European Journal of Inorganic Chemistry

Current research reports and chronological list of recent articles.

The scientific European Journal of Inorganic Chemistry - EurJIC - is the fastest growing journal in inorganic chemistry. It publishes Full Papers, Short Communications, and Microreviews from the entire spectrum of inorganic, organometallic, bioinorganic, and solid-state chemistry.

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Additional research articles in the field of inorganic chemistry, see Current Chemistry Research Articles. Magazines with similar content:

 - Dalton Transactions,

 - Inorganica Chimica Acta,

 - Inorganic Chemistry,

 - Inorganic Chemistry Communications,

 - European Journal of Inorganic Chemistry,

 - Russian Journal of Inorganic Chemistry.

European Journal of Inorganic Chemistry - Abstracts

Syntheses of Sterically Bulky Schiff-base Magnesium Complexes and Their Application in the Hydrosilylation of Ketones

The sterically bulky Schiff-base ligand 1 (L1H) was treated with CH3MgI in toluene to give the unexpected homoleptic magnesium complex 2 (L1MgL1) in good yield. However the reaction of more sterically bulky ligand 3 (L2H) with CH3MgI in diethyl either yielded the desired heteroleptic magnesium iodide 4 (L2MgI(OEt2)) which was further reduced with sodium to produce the MgNa heterobimetallic complex 5. The crystal structures of all new magnesium complexes were determined by single crystal X-ray diffraction. All new magnesium complexes have been investigated as catalysts for the hydrosilylation of ketones with (EtO)3SiH. The study showed that catalytic activity of the MgNa bimetallic complex 5 is superior to those of monometallic magnesium complexes 2 and 4 and is applicable to a series of subatrates.
Datum: 26.08.2016

An OFF-ON-OFF fluorescent sensor for pH windows based on the 13aneN4: Zn2+ system

The new ligand L was prepared, featuring a 13-membered tetraaza macrocyclic ring and a 1,8-naphtalimide fluorophore appended on a C atom of its backbone. The protonation constants of L as well as its complexation constants with Zn2+ have been determined in 1:1 water:methanol solution by potentiometric titrations. pH-fluorimetric titrations have been carried out both on L alone and in the presence of 1:1 Zn2+ and compared with the % vs pH species distribution. A window-shaped fluorescence trend was observed with pH for the L/Zn2+ system, that behaves as an OFF-ON-OFF pH sensor. The ON window is centered in the 6.5-7.5 pH range, in correspondence with the formation of [ZnL]2+. L also works as a Zn2+ sensor in such pH window, that includes the physiological pH value (7.4). Accordingly, L was used as a probe capable of visualizing the Zn2+ pools in Saccharomyces cerevisiae yeast cells at pH 7.4, with the additional ability of distinguishing between living and dead cells.
Datum: 26.08.2016

Optimal Size-Matching and Minimal Distortion Energy: Implications for Natural Selection by Macrocycle of Iron Species in Heme

In heme, a porphyrin macrocycle naturally selects iron ionic species. It is found that this natural combination is directly related to the geometry sizes of both components. Three series of monostrapped nonplanar metalloporphyrins [M = Fe(III)Cl, Co(II), Ni(II)] and their metal-free counterparts were synthesized as model systems, and their core sizes were compared, and density functional theory computations were used to calculate the molecular distortion energies. The results indicate that optimal size-matching of both is to maintains the minimal distortion energy of the macrocycle. This shows that the mutual selection process between the macrocycle and the metal ion is mainly based on the principle of minimum energy for tuning the electronic structure of the central metal ion; this may be a common principle in natural tetrapyrroles containing metal species. The structural parameters of all the model compounds were directly obtained from their crystal structures.
Datum: 26.08.2016

The Activation of CO2, CS2 and the Formic Acid Dehydrogenation Catalyzed by Iron(II) Hydride Complexes

Fluoroarylimine-stabilized iron(II) hydrides were used for the activation of CO2. The resulting iron(II) formate complex 6, which was obtained by formal CO2-insertion into the Fe-H bond, turned out to be unstable in solution. CO was found to be beneficial for the formation of stable analogues of complex 6. From the three-component reaction of CO, CO2 and iron hydride, a series of stable carbonyl formate iron(II) complexes (7 - 9) was generated. The iron(II) formate complex 6 could also be obtained from the reaction of iron(II) hydride complex with formic acid. Based on this result, the formic acid dehydrogenation reaction catalyzed by iron(II) hydrides was explored. The reaction was monitored by in situ 1H NMR spectroscopy and a possible mechanism was proposed. In addition, iron(II) hydrides could also react with CS2 to generate thiocarboxy iron(II) complexes (12, 13, 14 and 16). An unexpected complex 17 was produced from the three-component reaction of CS2, 4 and compound 15. The possible mechanism of the three-component reaction was also studied through the operando IR monitor.
Datum: 26.08.2016

Synthesis and in vitro toxicity of D-glucose and D-fructose conjugated curcumin ruthenium complexes

A series of carbohydrate conjugated bisdemethoxycurcumin (BDC) ligands were synthesized by using the Huisgen copper(I) catalyzed cycloaddition between azido-functionalized D-glucose and D-fructose as well as propargyl modified BDC. The unprotected sugar ligands were reacted with Ru(bpy)2Cl2 to form curcumin conjugated Ru-complexes of the general formula Ru(bpy)2(L)Cl. Ligands as well as Ru complexes were analyzed by NMR, IR, UV/Vis and fluorescence spectroscopy, mass spectrometry as well as elemental analysis (EA). Incubation of L929, HepG2 and the breast cancer cell line MDA-MB-231 revealed lower cytotoxicity of all carbohydrate conjugated ligands compared to BDC. The Ru-complexes exhibited higher cytotoxicity as the parent ligands in particular against HepG2 cells, whereas the non-cancerous L929 cell line remained unaffected. Unlike expected, the D-fructose conjugated ligand and its corresponding Ru complex did not show any significant toxicity against MDA-MB-231 cells.
Datum: 26.08.2016

Indenyl compounds with constrained hapticity: the effect of strong intramolecular coordination.

A series of cyclopentadienyl and indenyl molybdenum(II) compounds with intramolecularly coordinated pyridine arm, including scorpionate-like species bearing two irreversibly coordinated arms on the indenyl core, was synthesized and characterized. All presented structural types were confirmed by X-ray diffraction analysis. Due to strong nucleophilicity of pyridine, the intramolecular interaction is considerably stronger than in case of analogous species bearing tertiary amines in the side chain. Although the starting compounds for syntheses are isostructural, the reaction outcomes differ considerably. The cyclopentadienyl precursor gives a pentacoordinated 5:N-compound while the indenyl analogue produces a hexacoordinated species with unprecedented 3:N-coordination mode of the indenyl ligand representing an unusual example of so-called indenyl effect. The unusually high stability of the 3:N-coordination compounds toward 3 to 5 haptotropic rearrangement was clarified by theoretical calculations. As the strong intramolecular interaction prevents rotation of the indenyl, it cannot reach the conformation suitable for the 3 to 5 rearrangement. As the result, the low hapticity is effectively locked.
Datum: 24.08.2016

Transition Metal Complexes with Ferrocene-Bridged Bis(imidazolin-2-imine) and Bis(diaminocyclopropenimine) Ligands

The reaction of the ferrocene-bridged bis(imidazolin-2-imine) ligand N,N-bis(1,3-diisopropyl-4,5-dimethylimidazolin-2-ylidene)-1,1-ferrocenediamine, fc(NIm)2, with MCl2 salts furnished the complexes [{fc(NIm)2}MCl2] (M = Mn, Fe, Co, Ni, Cu, Zn), which were structurally and spectroscopically characterized. The iron complex was oxidized by reaction with ferrocenium hexafluoroantimonate, and both compounds, [{fc(NIm)2}FeCl2] and [{fc(NIm)2}FeCl2]SbF6, were further studied by means of Mössbauer spectroscopy, SQUID magnetometry and single-crystal X-ray diffraction, revealing that oxidation occurred at the tetrahedral FeN2Cl2 moiety. The CuX (X = Cl, Br, I) complexes of fc(NIm)2 were synthesized, affording dimeric (X = Cl, Br) or polymeric (X = I) structures. In addition, the ligand fc(NCyp)2, bis(N,N,N',N'-tetraisopropyl-2,3-diaminocyclo-propen-1-ylidene)-1,1'-ferrocene¬diamine, was prepared and the trimetallic complex [{fc(NCyp)2}Pd2Cl4] was synthesized and structurally characterized. The attempted synthesis of the corresponding nickel complex furnished single crystals of the composition [{fc(NHCyp)2}Cl(NiCl3)]; X-ray diffraction analysis afforded the first crystal structure of the [Ni2Cl6]2- anion.
Datum: 24.08.2016

Synthesis, Structure and Gas-phase fragmentation of Trinuclear Mo3S4 Clusters Bearing Aminophosphine Ligands: A Combined Experimental and Theoretical Study

Aminophosphine [Mo3S4X3(edpp)3]+ cluster complexes, 1+ (X=Cl) and 2+ (X=Br) (edpp= 2-aminoethyl)diphenylphosphine) have been quantitatively prepared by reacting the molecular[Mo3S7X6]2- anion with the edpp ligand in a one-pot synthetic procedure. Alternatively, complexes 1+ and 2+ can be synthesized using polymeric {Mo3S7X4}n phases as metal precursors. Their crystal structure show the incomplete cubane-type Mo3S4 cluster core as well as the formation of a unique isomer in which the nitrogen atoms of the amino group and the halide atoms are located above the trimetallic plane. Gas phase reactivity studies on complexes 1+ and 2+ show the subsequent elimination ofneutral HX (X=Cl,Br) molecules under collision induced dissociation (CID) conditions. The fragmentation pattern of 1+ and 2+ in combination with gas-phase DFT calculations are contrary to the general idea on the hemilabile character of the aminophosphine ligands and give support to the formation of unsaturated molybdenum/imine Mo=NH species. Based on DFT calculations, two competitive mechanisms involving a proton transfer from the amino group to a halide ligand attached to the geminal or to the vicinal molybdenum center are proposed. The first mechanism, which is a proton transfer within the nitrogen and halogen atoms bound to the same metal, is energetically favored.
Datum: 24.08.2016

Self-assembly of a tri-lanthanide(III) core sandwiched between two thiacalix[4]arene ligands

Thiacalix[4]arene-p-tetrasulfonate (TCAS) incorporated a tri-lanthanide(III) core to form a 3:2 Ln3TCAS2 complex in aqueous solution. The self-assembly process was monitored at pH 9.5 and 7.4 by HPLC for all lanthanides except PmIII. Self-assembly took place in three steps. First, TCAS and LnIII formed a 1:1 Ln1TCAS1 complex. Second, two molecules of Ln1TCAS1 condensed to form Ln2TCAS2. Finally, Ln2TCAS2 reacted with additional LnIII to form Ln3TCAS2. This self-assembly exhibited extremely slow kinetics and required 1-4 days to reach completion. Small amounts of minor species, including Ln1TCAS1, Ln2TCAS2, and Ln4TCAS2, were observed depending on the LnIII species and pH. The generation of these species is controlled by factors such as the stability of the Ln-TCAS species, effect of coordinated water, and size of LnIII. XAFS spectra of aqueous Gd3TCAS2 solutions established the solution structure of the tri-LnIII cluster sandwiched by two TCAS ligands.
Datum: 24.08.2016

Oxidized Styrylruthenium Ferrocene Conjugates: From Valence Localization to Valence Tautomerism

We report on ferrocenyl styryl ruthenium conjugates FcC6H4CH=CHRu(CO)(PiPr3)2(L) where the electron density at the ruthenium alkenyl site is modified by the variation of coligand L (L = Cl, acac, hfac, or dpvm). Crystallographic studies on three derivatives provide snapshots of the conformational degrees of freedom for rotation around the vinyl-phenylene and the phenylene-ferrocenyl linkages. All four complexes undergo two consecutive, reversible one-electron oxidations, whose potentials depend on the ligand L. According to IR spectroelectrochemistry, the first oxidation of the less electron-rich chloro and hfac complexes is strongly biased towards the ferrocenyl site. The radical cation of the acac complex, however, exists as two equilibrating valence tautomers (VTs) Fc+C6H4CH=CH{Ruacac}Fc[C6H4CH=CH{Ruacac}]+ ({Ruacac = Ru(CO)(PiPr3)2(acac)), where the positive charge is either localized at the ferrocenyl site or delocalized over the styryl ruthenium moiety. Variable-temperature EPR and Mössbauer spectroscopy reveal that the ferrocenium valence tautomer dominates at low T. A marked solvent-dependence on the position and relative intensities of the separate Ru(CO) bands in the IR spectra reveals environmental effects on the relative stabilities of the two VTs, while the strong negative solvatochromism of the prominent near IR band of the radical cation of the acac complex argues for a sizable (intervalence) charge-transfer component of the underlying excitation.
Datum: 24.08.2016

Group 11 Metal Complexes with Unsymmetrical Bifunctional Ferrocene Ligands

The reactions of two unsymmetrical P^N (L1) and P^P (L2) ferrocene ligands towards group 11 metal complexes have been studied. L1 shows a different behaviour with the three metals. Gold forms mononuclear derivatives with coordination of the metal to the phosphorus atom, whereas the reaction with silver(I) or copper(I) complexes affords mononuclear or dinuclear compounds in which both donor atoms, phosphorus and nitrogen, are involved in the coordination to the metal. The reactions of the diphosphine ligand [Fc(CH2PPh2)(PPh2)] L2 with gold(I), gold(III), silver(I) or copper(I) complexes afford mono, di or trinuclear derivatives. Some homo and heterodinuclear compounds have been obtained by the reaction of the mononuclear gold(III) complex [Au(C6F5)3{Fc(CH2PPh2)(PPh2)}] (6), in which one of the phosphorus atoms is free, with gold(I), gold(III) or silver(I) derivatives. Some of these derivatives have been characterized by X-ray diffraction.
Datum: 23.08.2016

Unexpected Formation and Crystal Structure of the Highly Symmetric Carbanion [C(SiCl3)3]-

Disproportionation reactions of Si2Cl6 in the presence of [n-Bu4N]Cl in halogenated solvents yield the compound [n Bu4N][C(SiCl3)3] (1). The X-ray structure analysis of 1 proves the existence of a planar carbanion, which is stabilized by three trichlorosilyl groups. Quantum chemical analysis shows the presence of highly polar bonds in the anion. Planarization of the anion can be explained by interaction of the occupied lone pair at the carbon atom with the antibonding * orbitals of the Si-Cl bonds (negative hyperconjugation).
Datum: 23.08.2016

Self-assembled palladium and platinum coordination cages: Photophysical studies and anticancer activity

Self-assembled coordination cages are interesting as drug delivery systems. Therefore, the synthesis of new ML (M = Pd, Pt) molecular cages, derived from highly fluorescent, rigid polyaromatic ligands is reported and the first PtL cage with a ligand consisting of three pyridine moieties is described. Photophysical properties were examined showing high quantum yieldsof up to 48% for the methoxy-functionalized ligands. Coordination of the ligands to palladium and platinum ions reduces the metallocages' fluorescence, however. The host-guest chemistry of the palladium cage with cisplatin is investigated confirming the encapsulation. The cages encapsulating cisplatin show a significantly increased cytotoxicity towards A549 (human lung adenocarcinoma) cells compared to cisplatin, and thus appear to be promising delivery vectors for the anticancer drug cisplatin.
Datum: 23.08.2016

A Palladium(II) Peroxido Complex Supported by the Smallest Steric N-heterocyclic Carbene, IMe (IMe = 1,3-Dimethylimidazole-2-ylidene), and Its Reactivity by Oxygen Atom Transfer

Stabilized with an NHC ligand of the smallest steric profile, Pd(II)(²-O)(IMe) was synthesized by direct addition of dioxygen to Pd(0)(IMe). The peroxido palladium complex with IMe, which was previously available by only computation, was characterized with IR and X-ray crystallography. Moreover, its oxo-atom transfer reactivity was elucidated by studying 1) thermolysis in pyridine at 60°C to yield IMeO, and 2) reaction with oxygen atom transfer (OAT) acceptors such as PPh and (MeSi).
Datum: 23.08.2016

Capillary Zone Electrophoresis as a Tool to Monitor the Stability and Hydrolytic Equilibria of Strandberg-Type Polyoxometalates in Aqueous Solution

In this study, we applied capillary zone electrophoresis (CZE) to investigate the solution stability and equilibria of pentamolybdobis(phenylphosphonate), [(C6H5PO3)2Mo5O15]4–, which is a Strandberg-type of polyoxometalate (POM) with considerable promise as an antiviral and anti-HIV chemotherapeutic agent. This is achieved by analyzing the intensities and shapes of the three peaks in the CZE electropherogram that correspond to the three components involved in the equilibria, that is, [(C6H5PO3)2Mo5O15]4–, [Mo7O24]6–, and [Mo8O26]4– anions. The dependence of the equilibria of pentamolybdobis(phenylphosphonate) on various conditions, including sample concentration, counterion, and solution pH, was investigated through CZE. The interactions of pentamolybdobis(phenylphosphonate) with amino acids and cyclodextrins in solution were also investigated and discussed on the basis of the CZE results. Our study indicates that CZE has great potential as a simple, low-cost, and efficient method to monitor the synthesis, purity, stability, and solution equilibria of POMs.Capillary zone electrophoresis is used to monitor the effects of sample concentration, counterion, and solution pH on the stability and equilibria of pentamolybdobis(phenylphosphonate).
Datum: 22.08.2016

A new 3D Cu(II)-based energetic MOF: Synthesis, structure and energetic performance

A new energetic MOF, [Cu2(TO)(DNS)(H2O)]n (1) (H2TO = 1,2,4-triazole-5-one, H2DNS = 3,5-dinitrosalicylic acid), has been synthesized and structurally characterized. Single crystal X-ray diffraction indicates that 1 possess compact 3D architecture. Noteworthily, two oxygen atoms of nitryl coordinate to two Cu(II) ions with syn-anti mode, which is further decrease the sensitivity but no influence on the explosive property. Based on TG and DSC analyses results, a rapidly thermal decomposition process and superior thermostability exist in 1. The non-isothermal kinetic for exothermic process of 1 is studied by Kissinger's and Ozawa's methods. The sensitivity tests and calculated detonation property show that 1 can be used as potential green explosives.
Datum: 22.08.2016

Hexaethyltripyrrindione (H3Et6tpd): A non-innocent ligand forming stable radical complexes with divalent transition metal ions

Nickel, palladium and copper complexes of the tripyrrolic ligand hexaethyltripyrrindione (H3Et6tpd) have been prepared and characterized by UV/Vis and EPR spectroscopy, as well as by single crystal X-ray structure determination. In all cases the metal ion is coordinated in a distorted square-planar geometry carrying a water ligand at the fourth coordination site. The Et6tpd ligand acts as a radical dianion in all cases. In solution, monomeric species are present in which the open-shell character of the ligand becomes apparent through EPR spectroscopic measurements. In the solid state, the compounds form polymorphs with tightly bound-dimers and chains showing small interplanar distances of 3.191-3.493 Å to one or more neighboring molecules. Magnetic measurements confirm the radical character of the tripyrrindione ligand and reveal strong intermolecular magnetic interactions for these complexes.
Datum: 22.08.2016

Multiferrocenyl Cobalt-based Sandwich Compounds

The reaction of FcCC-CCFc (Fc = Fe(5-C5H4)(5-C5H5)) (1) with Co(5-C5H5)(CO)2 (2) afforded ferrocenyl-functionalized cyclobutadiene and cyclopentadienone cobalt(I) compounds as well as multiferrocenyl benzene derivatives. The synthesis procedures are described. Eleven products could be separated by column chromatography and were characterized by NMR, UV-Vis and IR spectroscopy, high resolution ESI-TOF mass spectrometry and elemental analysis. For five representatives the structure in the solid state was determined by single X-ray structure analysis. The electronic properties of the appropriate compounds were studied using cyclic and square-wave voltammetry. Further investigation of the interaction between Fe(II)/Fe(III) centres in the mixed-valent species was achieved by in situ UV-Vis/NIR spectroelectrochemistry. These measurements demonstrated that weak electronic metal-metal interactions through the cobalt- coordinated cyclobutadiene building block occur (weakly coupled class II systems according to the classification of Robin and Day), while the cyclopentadienone core acts as insulator (class I) and hence only electrostatic interactions are characteristic.
Datum: 22.08.2016

Synthesis, Electronic Spectroscopy, Photophysics and Electric Properties and X-ray Molecular Structures ofthe Aza Ligands tetrakis[4-(benzoyloxy)phenyl]porphyrinatoComplexes

The synthesis of the new meso-porphyrin namely, tetrakis[4-(benzoyloxy)phenyl]porphyrin (H2TPBP), the meso-(tetrakis[4-(benzoyloxy)phenyl]porphyrinato)zinc(II) starting material complex [Zn(TPBP)] (1) and the 1,4-diazabicyclo[2.2.2]octane (dabco), pyrazine (pyz), 4,4'-bipyridine (4,4'-bpy), 4,4'-diaminodiphenylmethane (4,4'-mda) and the 4-cyanopyridine (4-CNpy) coordination compounds with the TPBP porphyrinate complexes (1-7 respectively) are described. The pyrazine derivative crystallizes as bis-pyrazine six-coordinated zinc metalloporphyrin (4). Complex 5 is present in solid state as a dimer with the 4,4'-bpy acting as a bridging ligand while in solid state, the 4,4'-mda species (6) is a five-coordinated monomer zinc derivative. All structures of 2-6 possess cavities with different dimensions where are located the solvent molecules. The solution UV/Vis spectra of 2-7 exhibit redshifted Soret bands indicating that these derivatives in solution are five-coordinated zinc(II) porphyrin complexes. The proton NMR of these species also confirms this deduction. The photophysical proprieties of 1-7 are similar to those of zinc(II) meso-porphyrins related species. The cyclic voltammetry of the H2TPBP free base and 1-7 present a third one-electron reversible oxidation wave. Single-layer diode devices of the [iridium tin oxide / zinc porphyrins (1-7) / aluminum] configurations show relatively low turn-on voltages.
Datum: 22.08.2016

Multi-Ferrocenyl Aryl Ethers - Applying the Nucleophilic Aromatic Substitution Reactions on Aryl fluorides

The reaction of ferrocenol (FcOH; Fc = Fe(C5H5)(C5H4) with aryl fluorides ArH6-nFn (n = 3 - 6) within a nucleophilic aromatic substitution reaction (SNAr) gave ferrocenyloxy-substituted fluoro benzenes of general type C6H0-3F1-5(OFc)1-5. For 1,3,5-C6H3F3 one, for 1,2,4,5-C6H2F4 two and for C6H6-nFn (n = 5,6) three F atoms could be replaced by FcO units. The reaction of 1,4-(OFc)2-C6F4 with additional amounts of FcOH afforded the tetra- and penta-substituted arenes 3,6-F2-C6(OFc)4 and C6F(OFc)5. Electrochemical investigations of both compounds showed four or five Fc/Fc+ related reversible redox processes that were attributed to electrostatic interactions. The addition of C6F6 as the electrophile after the anionic phospho-Fries rearrangement of a ferrocenyl phosphate (1,3-O->C migration) to the 1,2-substituted ortho-phosphonato ferrocenol, resulted in the formation of the respective ortho-functionalized ether. The constitution of all compounds was verified by using 19F NMR spectroscopy. Steric hindrance of the ortho-substituent resulted in a doubling of the signal sets for the C6F5 moiety in the 13C{1H} and 19F NMR spectra. The identity and substitution pattern of five compounds could also be determined by using single crystal X-ray diffraction analysis, revealing the 1,4-constitution of double functionalized derivatives, intermolecular non-classic C-HF interactions andinteractions.
Datum: 22.08.2016

Octaammine EuII and YbII Azides and Their Thermal Decompositions to the Nitrides

The common preparation for many nitrides is the synthesis from the corresponding metals and nitrogen at quite high temperatures and/or high pressures. Here we present a route to metal nitrides by the use of ammine metal azides under relatively mild conditions. Europium(II) and ytterbium(II) azides are prepared in liquid ammonia at –36 °C in form of their temperature-sensitive octaammine complexes. These were investigated by single-crystal X-ray diffraction at low temperatures, and their structures seem to be the first evidence for the existence of homoleptic ammine EuII and YbII complexes, as well as that the coordination number of these divalent cations can go beyond six with NH3 ligands. In one of the cases presented here the observed coordination polyhedron is better described as a bicapped trigonal prism (C2v), in one case better as square-antiprismatic (D4d). Warming of these compounds to room temperature leads to the lanthanoid metal azides still containing approximately 1 equiv. of ammonia. The behaviour of these azides towards further heating was investigated: By very careful and slow decomposition, the nitrides of europium(III) and ytterbium(III) are obtained at only 230 °C at ambient pressure. This method may be suitable to obtain other metal nitrides at remarkably low temperatures and pressures. EuII and YbII azides are prepared in liquid NH3 at –36 °C in form of their temperature-sensitive octaammine complexes. We present the first evidence for the existence of homoleptic octaammine EuII and YbII complexes. Warming of these compounds to room temperature leads to the lanthanoid metal azides still containing approximately 1 equiv. of ammonia. By slow thermal decomposition, EuN and YbN are obtained at only 230 °C at ambient pressure.
Datum: 22.08.2016

Spotlights on our sister journals: Eur. J. Inorg. Chem. 24/2016

Datum: 19.08.2016

Synthesis and Structural Characterization of Mono- and Bimetallic Rhodium(I), Iridium(I) and Gold(I) Methanide and Methandiide Complexes from 2-Quinolyl-Linked (Thiophosphoranyl)methane

Invited for the cover of this issue is the group of Wing-Por Leung at the Chinese University of Hong Kong, Shenzhen, P. R. China. The cover image shows the isolation of mono-, bi-, and polymetallic complexes derived from 2-quinolyl-linked potassium (thiophosphoranyl)methanide by simple metathesis reactions. A bimetallic gold(I) derivative with a strong aurophilic interaction was isolated…Read more about the story behind the cover in the Cover Profile and about the research itself on p. 3859 ff.
Datum: 19.08.2016

Front Cover: Synthesis and Structural Characterization of Mono- and Bimetallic Rhodium(I), Iridium(I) and Gold(I) Methanide and Methandiide Complexes from 2-Quinolyl-Linked (Thiophosphoranyl)methane (Eur. J. Inorg. Chem. 24/2016)

The cover picture shows the isolation of mono-, bi-, and polymetallic complexes derived from 2-quinolyl-linked potassium (thiophosphoranyl)methanide by simple metathesis reactions. The four different gear wheels represent four metal complexes. The biggest gear wheel represents the potassium salt, which is a useful synthon for preparing these complexes. By “pushing” the main gear wheel, we are able to isolate various metal complexes with different numbers of metal centers by using the appropriate metal halide; hence, these four gear wheels are in fact interrelated. Details are discussed in the article by W.-P. Leung et al. on p. 3859 ff. For more on the story behind the cover research, see the Cover Profile.
Datum: 19.08.2016

Dyads and Triads based on Phenothiazine, Bisterpyridine Ruthenium(II) Complexes and Fullerene

We report the modular synthesis of donor-photosensitizer-bridge-acceptor (D-P-B-A) triads and D-P dyads for the formation of photoinduced charge-separated species. The structures are based on a phenothiazine unit (D), a bisterpyridine ruthenium(II) complex (P), several phenylene(ethynylene)-type spacer units (B) and a pyrrolidino[60]fullerene (A) entity. The donor-acceptor distance is between 18 to 37 Å and was varied by four different bridging units. The photophysical and electrochemical characterization revealed certain interactions between the active moieties in the ground and the excited state. In particular, a reduced ruthenium-based emission in the triads indicates the occurrence of a quenching process mediated by the fullerene entity. Strong electrostatic interactions between the ruthenium(II) complex and the pyrrolidino[60]fullerene have been observed for the shortest triad, resulting in the strongest electron-accepting pyrrolidino[60]fullerene unit in the series.
Datum: 18.08.2016

Extended Sandwich Molecules Displaying Direct Metal-Metal Bonds

Treatment of [Cp*IrCl2]2 with Li[BH3(SePh)] at room temperature led to the isolation of dimetala analogue of hexaborane(10), nido-[(Cp*Ir)(µ-SePh)2Ir{(Cp*Ir)SePh}B4H8] 1. The solid state X-ray structure analysis of 1 shows a extended sandwich molecule with two iridium atoms between a pentamethyl-cyclopentadienyl (Cp*) and [B4Ir] ring. Further, in an effort to synthesize the Rh analogue of 1 under similar reaction conditions, we have isolated arachno-[{(Cp*Rh(µ-SePh)3}Rh(µ-SePh)B3H6], 2 a rhodium analogue of tetraboarane(10) in which the {RhB3} unit showed a geometric equivalence with a metal -allyl {MC3} species. The Ir complex 1, having an Ir-Ir bond, can be considered similar to the di-zinc sandwich complex, [Cp*Zn-ZnCp*], in terms of the valence electron count (VEC) at the metal centers.
Datum: 18.08.2016

Exploring the Nature of the Nanocavity and Channels in Apoferritin and Apoferritin–Sodium Dodecyl Sulfate Complex Using an Enhanced Antenna Effect through the Encapsulation of EuIII–Tetracycline

The drug tetracycline hydrochloride (TC), which has cytotoxic and cytostatic effects on tumor cells, has been encapsulated within the nanocavity of apoferritin in the form of its EuIII complex (Eu3TC). The Eu3TC complex was encapsulated within apoferritin through disassembly followed by reassembly of the protein and exhibited significantly enhanced EuIII emission in comparison with that of free Eu3TC in aqueous buffer at pH 8. The steady-state and transient measurement of the emission of each species in the ternary system suggest that the effective sensitization of EuIII emission may be ascribed to a comparatively rigid environment for the bound TC after encapsulation that promotes efficient energy transfer to the EuIII ions. Emission studies in D2O revealed that the microenvironment of the EuIII ion is shielded from O–H oscillators in the ternary system, and the extent of shielding is greater after the encapsulation of the complex within the apoferritin cavity. The rotational correlation time (θc) of bound TC and docking studies also support the contention that the TC is in a more buried environment after encapsulation within the apoferritin cavity. A competition study with sodium dodecyl sulfate (SDS) revealed that SDS does not interfere with the binding of TC to apoferritin. The biocompatible system consisting of Eu3TC encapsulated within the cavity of apoferritin may be used as an efficient targeted drug transporter, and the sensitization of the EuIII emission may also enable its use as a biosensor.The drug tetracycline (TC) as Eu3TC is encapsulated within the nanocavity of apoferritin through disassembly then reassembly of the protein and exhibits significant enhancement of the EuIII emission in comparison with that of free Eu3TC in aqueous buffer at pH 8. This simple system with Eu3TC encapsulated within the cavity of apoferritin may be used for efficient targeted cancer therapy.
Datum: 16.08.2016

Reactions of the Lithiated Diphosphine tBu2P–P(SiMe3)Li with [(η6-C6H6)RuCl2]2 in the Presence of Tertiary Phosphines

tBu2P–P(SiMe3)Li reacted with [(η6-C6H6)RuCl2]2 at –40 °C in the presence of PR3 (PR3 = PEt3, PEt2Ph, PEtPh2) by the nucleophilic addition of the tBu2P–P(SiMe3) moiety to the benzene ring to yield solely the complexes [(R3P)2Ru(Cl){η5-C6H6(Me3SiP–PtBu2)}] (1). These products decomposed slowly at ambient temperature to yield benzene, Ru clusters, and small amounts of the dinuclear ruthenium complexes [{(R3P)2Ru}2(µ,η2:2-P2)2Ru(PR3)2] (Ru–Ru) (6). Single-crystal X-ray diffraction studies of [(PhEt2P)2Ru(Cl){η5-C6H6(Me3SiP–PtBu2)}] (1b) and [(Ph2EtP)2Ru(Cl){η5-C6H6(Me3SiP–PtBu2)}] (1c) revealed that the addition of the tBu2P–P(SiMe3) group occurred through an exo pathway. Complex 6a (R = Et) displays a planar rectangular P4 system consisting of two P2 units and a Ru–Ru distance that lies in the range of a single bond.Nucleophilic addition to a coordinated benzene ring. tBu2P–P(SiMe3)– attaches to the benzene ring in [(η6-C6H6)RuCl2]2 in the presence of a tertiary phosphine to form unstable [(Et3P)2Ru(Cl){η5-C6H6(Me3SiP–PtBu2)}]. This complex decomposes to give dimeric Cl-bridged RuII complexes together with several phosphorus compounds. In the presence of tBu2P–P(SiMe3)Li it yields [{(Et3P)2Ru}2(µ,η2:2-P2)2].
Datum: 16.08.2016

Structure and Antiferromagnetism of Trinuclear Heterometallic Strings Containing MnII–MII–MnII Frameworks (M = Ni, Pd, Pt)

The syntheses, crystal structures, and magnetic properties of three trinuclear, symmetric, heterometal string complexes stabilized by four dipyridylamide (dpa) ligands were explored. MnNiMn(dpa)4Cl2 (1), MnPdMn(dpa)4Cl2 (2), and MnPtMn(dpa)4Cl2 (3) were found to exhibit an approximate D4 symmetry and a linear metal framework helically wrapped by four syn–syn-type ligands. The center metal ions bond with the amide part of dpa– in a square-planar environment, and the outer Mn ions bond with Cl– and the pyridyl part of dpa– in a square-pyramidal environment. The magnetic susceptibilities of these three compounds showed antiferromagnetic interactions (2J = –13.7 cm–1 for 1, –29.7 cm–1 for 2, and –66.2 cm–1 for 3 in the Heisenberg exchange framework) between the MnII magnetic centers. The value of 2J increased with increasing atomic number of the central metal ion. The antiferromagnetic properties were further confirmed by electron paramagnetic resonance spectroscopy studies in variable-temperature measurements.MnMMn(dpa)4Cl2 (M = Ni, Pd, Pt; dpa = dipyridylamide) shows antiferromagnetism and special electron paramagnetic resonance (EPR) spectroscopy patterns. The antiferromagnetic interaction increases with increasing atomic number of the central metal ion. The antiferromagnetic properties are further confirmed in the EPR studies in variable-temperature measurements.
Datum: 16.08.2016

Evaluation of Perylene Bisimide-Based RuII and IrIII Complexes as Photosensitizers for Photodynamic Therapy

The synergistic action of a photosensitizer (PS), light, and oxygen is exploited in photodynamic therapy (PDT) to kill cancer cells with reduced side-effects compared with traditional chemotherapeutic treatments. In this regard, new PSs are still necessary to improve the efficacy and the outcomes of this medical technique. Over the past years, metal complexes have attracted interest as alternatives to traditional porphyrin and phthalocyanin-based PSs because of their tunable and thus tailor-made photophysical properties. Among others, RuII and IrIII derivatives have shown promising results. Here, we report on the investigation of [Ru(bpy)2(ab-PBI)][PF6]2 (1) and [Cp*Ir(ab-PBI)Cl]PF6 (2), where bpy = 2,2′-bipyridine, ab-PBI = azabenz-annulated perylene bisimide, and Cp* = pentamethylcyclopentadiene, as potential PDT PSs. These compounds display good photostability, as well as interesting singlet oxygen generation upon irradiation at 420 nm (in particular 2). Their biological activity was evaluated on four cell lines and, although the cytotoxicity of 1 did not improve significantly upon light irradiation, 2, which localizes in mitochondria of HeLa cells as indicated by ICP-MS measurements, reached nanomolar IC50 values on all the cell lines tested when activated with 420 nm light in low doses (9.27 J cm–2). The biological activity of a RuII polypyridyl complex 1 and an IrIII organometallic complex 2 on four cell lines is presented. Although the cytotoxicity of 1 did not improve significantly upon light irradiation, 2 reached nanomolar IC50 values on all the cell lines tested when activated with 420 nm light in low doses.
Datum: 16.08.2016

A Highly Robust Terbium Coordination Polymer as a Multiresponsive Luminescent Sensor for Detecting Pollutant Anions

An extremely stable Tb coordination polymer, TbL2 [HL = 4-(pyrimidin-5-yl)benzoic acid], was synthesized. It exhibits high thermal and chemical stability. TbL2 is a visual multiresponsive luminescent probe that can selectively detect F– among the same main-group anions as well as various pollutant phosphorus anions.TbL2 [HL = 4-(pyrimidin-5-yl)benzoic acid] is a multiresponsive sensor that is a highly sensitive detector for F– and various phosphates with many advantageous attributes such as open metal sites, open N-sites, as well as high chemical stability in water, over a wide pH range of 2–12, and thermal stability.
Datum: 16.08.2016

A Ferrocene based Phosphane/Borane Frustrated Lewis Pair for Asymmetric Imine Reduction

The -phosphanyl ferrocene carbaldehyde (pS)-1 was converted to the -styryl derivative (pS)-4 by Wittig-Horner olefination. Subsequent hydroboration with Piers' borane [HB(C6F5)2], followed by H2-splitting and crystallization gave the phosphonium/hydridoborate product (pS,R)-5, which was used as a FLP catalyst for the asymmetric hydrogenation of a series of imines (up to 69% ee).
Datum: 16.08.2016

The Interaction of 1,1'-Diphosphaferrocenes with Gold: Molecular Coordination Chemistry and Adsorption on Solid Substrates

1,1'-Diphosphaferrocene (1) and its 3,3',4,4'-tetramethyl (2), 3,3',4,4'-tetraphenyl (3), octamethyl (4), octaethyl (5) and octaphenyl derivative (6) have been investigated in terms of the suitability of 1,1'-diphosphaferrocenes as adsorbate species for fabricating self-assembled monolayers on gold. 3 and 6 have been structurally characterised by X-ray diffraction. The complexes [Au(4)2][GaCl4] and [Au2(mu-5)2][FeCl4]2 have been prepared and are only the second and third example to date of structurally characterised 1,1'-diphosphaferrocene gold complexes. [Au(4)2][GaCl4] exhibits intramolecular Au...Fe contacts compatible with Fe->Au bonding interactions, which have not been described before in ferrocene chemistry. [Au2(mu-5)2][FeCl4]2 exhibits an intramolecular Au...Au contact indicative of aurophilic bonding, leading to a structural motif unprecedented for 1,1'-diphosphaferrocenes. Ultrathin films obtained by chemisorption of the 1,1'-diphosphaferrocenes from solution onto gold substrates have been investigated by X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results indicate that the surface binding of 1 involves the Fe atom together with both P atoms, while in the other cases surface binding can be realised by just one phospholyl ring. There is no indication of any oxidative decomposition of the adsorbates on the surface. According to NEXAFS spectroscopic results 6 gives rise to SAMs of high orientational order.
Datum: 16.08.2016

Photoactivated functionizable tetracarbonyl phenylpyridine manganese(I) complexes as CO-releasing molecules: a direct Suzuki-Miyaura cross-coupling on a thermally-stable CO-RM

A new class of carbon monoxide-releasing molecules (CO-RMs) are reported based on a previously known tetracarbonyl phenylpyridine manganese(I) motif.A pre-functionalized CO-RM undergoes a direct Pd-catalysed Suzuki-Miyaura cross-coupling with phenylboronic acid to give a -extended three-ring CO-RM. Cross-coupling conditions were modified to allow coupling of a morpholine-containing boronic acid on to a CO-RM, introducing drug-like functionality. An LED system was used to facilitate controlled CO-release. Irradiation using an LED (400 nm or 365 nm) gives rise to faster CO-release, with lower overall input power compared to traditional use of a TLC lamp (365 nm), as measured by an assay based on the conversion of deoxymyoglobin to carbonmonoxymyoglobin.
Datum: 16.08.2016

Zinc chloride complexes with aliphatic and aromatic guanidine hybrid ligands and their activity in the ring-opening polymerisation of D,L-lactide

The synthesis of the new hybrid guanidine ligands TMGdmab, DMEGdmab, TMGdeab and DMEGdeab is reported. These ligands were combined with zinc chloride and the four new obtained complexes were structurally characterized by X-ray crystallography and NMR spectroscopy. Furthermore, eight new zinc chloride complexes were obtained by reaction of the hybrid guanidine ligands TMGdmae, DMEGdmae, TMGdeae, DMEGdeae, TMGdmap, DMEGdmap, TMGdeap and TEGdeap. All twelve complexes possess a tetrahedral coordination geometry. The donor situation between guanidine and amine donors was evaluated using density functional theory. These complexes show robust activity in the melt polymerization of technical unsublimed lactide. For selected complexes kinetic polymerization experiments have been performed which show first-order behavior. The end-group was proven by NMR spectroscopy.
Datum: 16.08.2016

[SiSxHy]n - Perhydridopolysilathianes - cross-linked thio-analogs of polysiloxanes

Polysiloxane-analogous Si-S-compounds have not been reported so far. Transsilylation reactions of the solid pyridine adduct of HSiCl3 with gaseous Me3Si-S-SiMe3 yield perhydridopolysila¬thianes. 29Si NMR, FTIR and Raman spectroscopy, elemental and thermal analysis, XRD, SEM and gas adsorption measurements indicate that the product consists of D-, T- and Q-units with a composition of ([H2SiS]1.2[HSiS1.5]2.6[SiS2]1.0)n. Formation of the latter is caused by pyridine catalysed dismutation reactions. The polymer is mesoporous with a surface area of 187 m²/g, amorphous and insoluble in organic solvents.
Datum: 16.08.2016

Hand in Hand: Experimental and theoretical investigations on the reaction of copper(I) mono- and bis(guanidine) complexes with dioxygen

Mono- and bis(guanidine) ligands stabilise bis-µ-oxido dicopper(III) complexes. Here, the formation of this complex has been investigated in detail using low temperature stopped-flow techniques for the monoguanidine 2-(3-(dimethylamino)propyl)-1,1,3,3-tetramethylguanidine (TMGdmap) and the related bis(guanidine) 1,3-bis(N,N,N',N'-tetramethylguanidino)propane (btmgp). Low temperature IR studies in solution support the formation of a bis-µ-oxido complex. For both systems, no intermediates could be detected on their way to the bis-µ-oxido complexes which is rationalised by extensive DFT calculations. In a first step, the oxygen reduction during the binding to the copper(I) complex to form a superoxido species is studied. In the second step, the full path from superoxido over trans-µ-peroxido to side-on-peroxido and finally bis-µ-oxido is modelled for singlet and triplet states. Hereby, a clear picture about the detailed reaction mechanism is gained which directly correlates with the observed activation enthalpies and reaction orders. The superoxido formation is rate-determining as pseudo-first order in copper(I) although the bis-µ-oxido formation is observed. The results illustrate the strength of density functional theory for the prediction of the reactivity of real-life systems.
Datum: 16.08.2016

A Mixed Porphyrin–Schiff Base Dysprosium(III) Single-Molecule Magnet

The mixed porphyrin–Schiff base potassium dysprosium(III) complex [K(TBPP)Dy(L)(CH3CN)2] [H2TBPP = 5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrin; H2L = N,N′-bis(3-methoxysalicylidene)benzene-1,2-diamine; 1] was isolated from the reaction between the metal-free Schiff base ligand H2L and the half-sandwich porphyrinato dysprosium compound [Dy(TBPP)(acac)] (Hacac = acetylacetone) in the presence of KOH. A sandwich-type double-decker structure has been unambiguously revealed by single-crystal X-ray diffraction analysis. Static and dynamic magnetic measurements disclosed the slow relaxation behavior of this new double-decker compound and indicated its single-molecule magnet (SMM) nature. Comparative studies on the magnetic properties of 1, the homoleptic bis[5,10,15,20-tetrakis(4-tert-butylphenyl)porphyrinato]dysprosium double-decker [DyH(TBPP)2] (2), and the bis(Schiff base)dysprosium double-decker {[Dy[Zn(L)Cl]2(DMF)2]·Cl} (3, DMF = N,N-dimethylformamide) indicate the effect of the ligand field (LF), through the deviation of the dysprosium coordination geometry from the ideal D4d form, on the SMM properties of 1–3 in addition to the effect of the charge distribution over the DyIII ion.A mixed porphyrinato–Schiff base potassium dysprosium(III) double-decker single-molecule magnet is synthesized and structurally characterized for the first time.
Datum: 16.08.2016

PhP=CPh2 and Related Phosphaalkenes: A Solution Equilibrium between a Phosphaalkene and a 1,2-Diphosphetane

The synthesis of phosphaalkenes, ArP=C(R)Ph (1, a: Ar = Ph, R = Ph; b: Ar = o-Tol, R = Ph; c: Ar = Mes, R = H), bearing sterically less hindered substituents is reported. Phosphaalkenes 1a–b were prepared by treating Ph2C=O with ArP(Li)SiMe3, whereas 1c was accessed from the AlCl3-mediated reaction of ArP(SiMe3)2 and PhC(O)H. Both 1a and 1b dimerize to afford their respective 1,2-diphosphetanes (2a and 2b). Compound 2a was characterized by X-ray crystallography. Dissolution of pure 2a in THF resulted in a temperature dependent equilibrium with monomer 1a (ΔHo = –94.6 ± 14.6 kJ mol–1; ΔSo = –284 ± 48 J mol–1 K–1). Although monomer E/Z-1c was identified in solution by its characteristic downfield 31P NMR chemical shift (δ = 247.1, 231.5), it was accompanied by the formation of what we believe are oligomers (δ = –25 to 10 ppm, br.). Attempts to trap phosphaalkenes 1a and 1b by treatment with W(CO)5(MeCN) afforded mixtures of complexes W(CO)5(1a–b) (4a–b) and W(CO)4(1a–b)2 (5a–b), the disubstituted species being subjected to X-ray crystallographic characterization (5a).The isolable 1,2-diphosphetane [PhPCPh2]2 serves as a precursor to phosphaalkene PhP=CPh2 in solution. This, and related phosphaalkenes may be isolated as tungsten(0) complexes.
Datum: 16.08.2016

σ-Bond Activation in Aluminium-Functionalized Alkynylchlorogermanes: Facile Insertion of Isocyanate and Azide into Al–C and Ge–Cl Bonds

Hydroalumination of Cl-functionalized alkynylgermanes yielded mixed Al/Ge compounds (1). The Cl atoms adopted bridging positions between the Ge and Al atoms to form four-membered GeCAlCl heterocycles with relatively long endocyclic Ge–Cl and Al–C bonds. Reactions with isocyanates resulted in the insertion of the heterocumulenes into both activated bonds and the formation of four-membered GeC2N heterocycles, which featured exocyclic C–C and C–O double bonds with C–O oxygen atoms coordinated to ClAltBu2 molcules (2). An intermediate (3) was isolated with Ad-NCO (Ad = 1-adamantyl) from the insertion of isocyanate into the endocyclic Al–C bond. These products are characterized by intact Ge–Cl bonds and a chelating coordination of the Al atoms by the OCN groups. They rearranged at elevated temperature to yield compounds of type 2. Quantum-chemical calculations were applied to evaluate the thermodynamics of these isocyanate insertion reactions. An azide reacted similarly by insertion into the Al–C and Ge–Cl bonds and afforded a GeCN3 heterocycle with an intact N3 group.σ-Bond activation results from an intramolecular interaction between Al and Cl atoms in dialkylaluminum-functionalized chlorogermanes. The concomitant weakening of the Ge–Cl and Al–C(vinyl) bonds facilitates insertion reactions with isocyanate and azide and the formation of unusual structural motifs by C–C and C–N bond formation.
Datum: 16.08.2016

A {Cu4I4} Cluster Supported on a Metal-Dithiolato Complex Anion Causes its Conformational Change Leading to a Doubly-Bridged Curved Coordination Polymer and its Reactivity with a Diamine Resulting in the Emergence of a [M(diamine)(dithiolate)] System

When dithiolene-based coordination complexes [Bu4N]2[MII(tdas)2] (tdas2– = 1,2,5-thiadiazole-3,4-dithiolate; M = Ni, Pd, Pt) are reacted separately with CuI, it results in the formation of chain-like coordination polymers [Bu4N]2n[MII(tdas)2Cu4I4]n [M = Ni (compound 1), Pd (compound 2), Pt (compound 3)] in which each metal(bis)dithiolato complex unit supports a {CuI4I4} cluster unit. Two of the crystal structures and powder X-ray diffraction studies confirm that compounds 1, 2 and 3 are isomorphous with each other showing the abundance of a doubly-bridged “curved” chain-like structure formed by the coordination of two “N” donor atoms of each [MII(tdas)2]2– complex unit to two Cu+ ions of two adjacent {CuI4I4} cluster units and by the coordination of two Cu+ ions of a {CuI4I4} cluster with its neighbouring two [MII(tdas)2]2– complex anions through their “N” donor atoms from opposite sides. Since the [MII(tdas)2]2– complex anion generally has a planar geometry, which becomes bent upon supporting a {CuI4I4} cluster in the present study, the Cu–S interaction in [MII(tdas)2Cu4I4]2– is responsible for the bending conformation of the metal–dithiolato complex unit. This bending structure of the complex anion [MII(tdas)2]2– in [MII(tdas)2Cu4I4]2– describes a situation where the central part of the complex anion is pulled away towards the {CuI4I4} cluster through Cu–S bonds. This causes a “curve-like” structure throughout the resulting doubly-bridged chain in compounds 1, 2 and 3. The second important aspect of the present work is an interesting reactivity of this doubly-bridged coordination polymer with a bidentate chelating ligand, tetramethylethylenediamine (TMEDA). Compound [Bu4N]2n[NiII(tdas)2Cu4I4]n (1), a representative member of the series of compounds 1–3, was treated with TMEDA, which resulted in a square planar complex [Ni(tdas)(TMEDA)] (4) belonging to a mononuclear [MII(N2S2)]-type system (where N2 = bidentate N∩N donor ligand, mostly a bipyridine type, and S2 = dithiolato ligand) representing an important class of compounds for photophysical properties. Compound 4 exhibits emission at room temperature in the visible region.A dithiolene-based coordination complex, on treatment with CuI, results in the formation of a coordination polymer in which each metal(bis)dithiolene complex unit, undergoing a conformational change, supports a {CuI4I4} cluster unit.
Datum: 16.08.2016

Amidinium-Containing 2D [MnCr] Dimetallic Oxalate-Based Networks – The Influence on Structure and Magnetism Explored by Combining Experience and Theory

Three X2+ bisamidinium dications are inserted into oxalate-based dimetallic [MnCr] compounds of formula X[MnII(CH3OH)CrIII(ox)3]2·nS [X2+ = C14N4H202+ (cation A2+, compound 1), C14O2N4H202+ (cation B2+, compound 2), C16N4H242+ (cation C2+, compound 3); n = 4 (1–2), 2 (3); S = CH3OH (1–2), CH3CN (3); ox = oxalate]. Single-crystal X-ray analysis of 1–3 reveals that Mn–Cr oxalate-bridged dimetallic coordination networks form corrugated two-dimensional (2D) layers based on heptacoordinate MnII ions surrounded by six oxygen atoms from three bis-bidentate oxalate ions and one oxygen atom from a coordinated methanol molecule. In 1–3, the observed coordination environments of the MnII ions are close to capped trigonal prismatic (CTPR-7) according to continuous shape measurements (CSM). Curie–Weiss temperatures of 0.62, 0.42, and 0.54 K for 1–3, respectively, were deduced from the magnetic susceptibility measurements and reveal dominant ferromagnetic exchange interactions. Ab initio calculations up to the DDCI-2 level were performed on [MnCr] dimeric units and allowed the evaluation of the exchange interactions in 1–3. Three oxalate-based dimetallic [MnCr] compounds with intercalated bisamidinium dications are studied, and magnetostructural correlations are provided.
Datum: 16.08.2016

3,5-Dimethylpyrazolyl-Substituted Di- and Trisiloxanes

The synthesis and characterization of di- and trisiloxanes with 3,5-dimethylpyrazolyl (pz*) moieties are presented. Disiloxanes of the type O(SiMe3–npz*n)2 (n = 1, 2, and 3 in 2, 3, and 4, respectively) are easily accessible through a trans-silylation approach. Crystal structure analyses of compound 4 and the two side products 5 and 6 illustrate different coordination motifs of pz* (terminal vs. bridging) in the disiloxane system. The reaction of O2Si3Cl8 with Me3Sipz* led to the unsymmetrically substituted trisiloxane pz*3SiO-Sipz*2O-SiCl2pz* (7) with bridging pz* units and tetra- and pentacoordinate silicon atoms and the fully pyrazolyl-substituted trisiloxane O2Si3pz*8 (8), depending on the choice of the reaction conditions. The 29Si NMR properties of 7 were investigated by 29Si CP/MAS NMR spectroscopy and supporting quantum chemical calculations analyzing the principal components of the chemical-shift tensor for all three silicon atoms in this molecule. The reaction of 3,5-dimethypyrazolyltrimethylsilane with chloro-substituted disiloxanes and octachlorotrisiloxane afforded fully substituted disiloxanes and trisiloxanes. The properties of a special asymmetric trisiloxane (see picture) were investigated with respect to its formation and 29Si NMR shielding-tensor components.
Datum: 16.08.2016

Snap-Shots of a Reduction Pathway: The Reaction of WCl6 with Copper Powder

A combined differential scanning calorimetry (DSC)/X-ray diffraction (XRD) methodology is used to search and identify compounds in the Cu/W/Cl system based on the successive reaction of WCl6 with copper powder. Thermal effects monitored by DSC are used to detect reaction pathways and phase formations of compounds. A series of five new and one already known compounds is discovered as crystalline phases in the Cu/W/Cl system and structurally characterized by XRD. The reaction of WCl6 with elemental copper begins at temperatures as low as 60 °C with the formation of crystalline powders of α-CuxWCl6. Continuing reaction stages include the successive formation of crystalline phases β-CuxWCl6, γ-CuxWCl6, α-Cu2W2Cl10, β-Cu2W2Cl10, and Cu2[W6Cl14].A combined differential scanning calorimetry (DSC)/X-ray diffraction (XRD) methodology is used to investigate the successive reduction of WCl6 with copper powder. This approach shows the reductive intercalation of copper ions to yield α-CuxWCl6, β-CuxWCl6, γ-CuxWCl6, α-Cu2W2Cl10, β-Cu2W2Cl10, and Cu2W6Cl14.
Datum: 16.08.2016

Olefin/Paraffin Separation Potential of ZIF-9 and ZIF-71: A Combined Experimental and Theoretical Study

Two zeolitic imidazolate frameworks, ZIF-9 and ZIF-71, are evaluated by adsorption experiments and molecular simulations with respect to their potential towards olefin/paraffin separation. Pure component adsorption isotherms are measured and compared to grand-canonical Monte–Carlo (GCMC) simulations. The experiments show that the adsorption of the paraffin is favorable over the olefin in both structures. Whereas the isotherms are predicted well by simulations for ZIF-71, in case of ZIF-9 only the saturation loading could be computed accurately because the latter material seems to undergo a so-called gate-opening effect upon adsorption of guest molecules; ZIF-71 does not show this effect. Both structures show promising results with respect to olefin/paraffin separation. Experimental adsorption isotherms of ethane, ethene, propane, and propene on the metal-organic frameworks ZIF-71 and ZIF-9 have been compared to simulated isotherms, showing the potential of predicting the separation behavior of rigid and flexible adsorbents by grand canonical Monte–Carlo simulation.
Datum: 16.08.2016

The Role of Bulkiness in Haptotropic Shifts of Metal–Cumulene Complexes

In metal–cumulene complexes, the metal easily slides through the double bonds of the chain. A series of late-transition-metal–[5]cumulene complexes has been studied by theoretical and experimental methods in order to understand the factors that control such haptotropic shifts. The bulkiness of the cumulene terminal groups plays a central role in the tautomeric preferences. The quantum theory of atoms in molecules and the electron localizability indicator show that the M–C bond closer to the terminal groups is significantly weakened by steric interactions between these groups and the rest of ligands around the metal center. The results emphasize that special attention should be paid to the orientation of both the bulky substituents at the cumulene and other voluminous ligands around the metal, because the orientation of such moieties is important in predicting the direction of the haptotropic equilibrium correctly.To correctly predict the direction of haptotropic shifts in metal–cumulene complexes, not only is the bulkiness of terminal groups important, but also the orientation of these groups with respect to the remaining ligands around the metal center.
Datum: 16.08.2016

Molecular and Nanoaggregation in Cyclometalated Iridium(III) Complexes through Structural Modification

New terpyridyl ligands TP1, TP2 and cyclometalated iridium(III) complexes 1 and 2 based on these ligands have been synthesized. The ligands and complexes have been characterized by elemental analysis and spectroscopic studies (ESI-MS, 1H and 13C NMR, UV/Vis, fluorescence). The molecular structure of 1 has been verified by X-ray single-crystal analysis. It has been unambiguously established that variation of the substituents on 1 and 2 leads to molecular aggregation in 1, while 2 remains nonaggregated. Furthermore, complexes 1 and 2 have been successfully utilized as capping agents for the stabilization of gold nanoparticles (AuNPs). It is of note that 1 forms discretely, while 2 aggregates AuNPs through the assemblage of ultrasmall nanoparticles. It has been affirmed by 1H NMR titration studies that –NH groups from 1 and 2 are involved in the capping of AuNPs. The role of simple structural variations in directing molecular and nanoaggregation has been clearly established for the first time by spectroscopic (UV/Vis, fluorescence, 1H NMR titration) and morphological studies [SEM, TEM, EDX (energy-dispersive X-ray), DLS (dynamic light scattering)]. The role of simple structural variations in directing molecular and nanoaggregation has been established for the first time in two new cyclometalated iridium(III) complexes with the help of various spectroscopic (UV/Vis, fluorescence, 1H NMR titration) and morphological analyses [SEM, TEM, EDX (energy-dispersive X-ray), DLS (dynamic light scattering)].
Datum: 16.08.2016

Neutral and Cationic Palladium Complexes of P-Stereogenic Phosphanes Bearing a Heterocyclic Substituent

The coordination chemistry of 13 optically pure P-stereogenic diarylmonophosphanes P(Het)PhR [Het = 4-dibenzofuranyl (DBF), 4-dibenzothiophenyl (DBT), 4-dibenzothiophenyl S,S-dioxide (DBTO2) and 1-thianthrenyl (TA); R = OMe, Me, iPr, Fc (ferrocenyl)] to Pd-allyl moieties is described. Both neutral [PdCl(η3-(2-methylallyl)(κP-P)] and cationic [Pd{η3-(2-methylallyl)(κP-P)2}]PF6 complexes have been prepared. Coordination of the heteroatom of the heterocycle was only possible in the case of TA-based phosphanes; these furnished complexes of the type [Pd{η3-(2-methylallyl)(κ2P,S-P)}]PF6 after chloride abstraction with TlPF6. The crystal structure of the complex [Pd(η3-2-methylallyl)(κ2P,S-PPh(OMe)(1-TA)]PF6 is reported. The neutral Pd complexes were found to be highly active in the hydrovinylation of styrene after activation with AgBF4, except for the TA-based phosphanes. The cationic Pd complexes were evaluated in allylic alkylation and amination with the model substrate rac-trans-1,3-diphenylprop-2-enyl acetate (rac-I), achieving total conversions and up to 70 % ee.The coordination chemistry of a series of P-stereogenic monophosphorus ligands, containing a heterocyclic substituent, towards the Pd-methallyl moiety has been studied. Some of the obtained complexes are very active in catalytic hydrovinylation whereas full conversion and a 70 % ee have been achieved in asymmetric allylic substitution.
Datum: 16.08.2016

In Situ Topotactic Synthesis of Monodispersed Hierarchically Nanostructured Yttrium-Based Microspindles from a Mesocrystal Precursor

Monodispersed hierarchically nanostructured yttrium-based materials including Y(OH)3, Y6O5F8, and H-NaYF4 were successfully synthesized from the same mesocrystal Y(OH)xF3–x precursor. It was found that there was a close crystallographic relationship between the precursor and the final products and all of the processes underwent an in situ topotactic transformation. Yttrium-based materials including Y(OH)3, Y6O5F8, and H-NaYF4 can be successfully synthesized from the same mesocrystal Y(OH)xF3–x precursor.
Datum: 16.08.2016

Synthesis and Conformational Study of Monosubstituted Aminoferrocene-Based Peptides Bearing Homo- and Heterochiral Pro-Ala Sequences

The synthesis and conformational analysis of a series of the monosubstituted aminoferrocene-based peptides bearing homo- and heterochiral Pro-Ala sequences are described. A change of the Pro amino acid chirality can affect the secondary structure. The homochiral derivatives of tBuCO–AA2–AA1–NHFc (Fc = ferrocene; AA = Pro, Ala) favour β-turns, and a disruption of the secondary structure is observed for the heterochiral analogues in solution. A detailed computational study suggested that γ-turns form in the heterochiral derivatives. The X-ray-determined crystal structures of the heterochiral compounds show a preference for β-turns. The calculated interaction energies indicate the significance of the intermolecular hydrogen bonds, which are favourable enough to overcome the rearrangement of a single molecule from the most stable conformer to that adopted in the solid state. The current research indicates the potential of the investigated compounds for the fine tuning of their conformational properties by variation of the chirality of the constituent amino acids.The synthesis and conformational analysis of monosubstituted aminoferrocene-based peptides bearing a Pro-Ala sequence indicate the potential fine tuning of the conformational properties by variation of the chirality of the constituent amino acids.
Datum: 16.08.2016

Dynamic directing effect and symmetric correlation in three pH modulated 1,4-diazabicyclo[2.2.2]octane/iodoargentate hybrids

Three iodoargentate hybrids, (HDABCO)(H2DABCO)(Ag3I6) (1), (HDABCO)2(H2DABCO)Ag3I7 (2) and [(H2DABCO·H2O)(AgI3)] (3) (DABCO = 1,4-diazabicyclo[2.2.2]octane), have been synthesized by simply changing pH value of reaction solution. 1 - 3 are all built by exclusive corner-sharing AgI4 tetrahedra, while they exhibit obvious different structural features (typical halozeotype in 1 and 2, chiral chain in 3). Noteworthy, variation in hydrogen bonded aggregating forms of DABCO at different pH value, regular modulation of inorganic moieties from [3276] cage in 1 to larger [32114] cage in 2 and three-fold helical chain in 3, as well as their intrinsic symmetric correlation reveal unique dynamic structural directing effects and flexible structural adaptability of iodoargentate framework. Moreover, three compounds display wide-bandgap semiconductor nature (band gaps about 3.70 eV for 1, 3.49 eV for 2 and 3.89 eV for 3) and photoluminescence properties (emission bands about 430 nm for 1, 467 nm for 2 and 460 nm for 3).
Datum: 12.08.2016

Enantioselective Synthesis of Ferrocene- or Cymantrene-Fused Planar-Chiral Phospholes

Planar-chiral ferrocene-fused phosphole (S)-1a was prepared in an enantiomerically pure form by the enantioselective transformation. The synthesis was starting with Kagan's chiral ferrocenyl acetal (-)-2a, and bromo- and (Z)-2-bromovinyl substituents were introduced at the 1- and 2-positions of the ferrocene platform in (S)-6a with controlling its planar chirality. The double Li/Br exchange on (S)-6a followed by the reaction with PhPBr2 provided (S)-1a in the excellent yield. The structure of (S)-1a was determined by X-ray crystallography. Planar-chiral cymantrene-fused phosphole (S)-1b was also prepared by the analogous asymmetric transformation starting with Jaouen's chiral cymantrenyl acetal (+)-2b.
Datum: 11.08.2016

Phenyl vs. Ferrocenyl Cyclometallation Selectivity: Diastereoselective Synthesis of an Enantiopure Iridacycle

Ferrocenyl (Fc) and phenyl (Ph) containing imines FcCH=NCH(R)Ph and FcCH(R)N=CHPh (R = H and Me) were cycloiridated using [Cp*IrCl2]2 with NaOAc in CH2Cl2. All resulted in the formation of neutral chloride ligated half-sandwich Iridacycles as a result of ortho-phenyl and not alpha-ferrocenyl C-H activation. The complexes derived from FcCH=NCH(R)Ph (R = H, Me) were obtained as a mixture of E and Z imine isomers, and with R = Me the product obtained from the (S)-imine was isolated by recrystallisation as a single diastereoisomer. The configuration was determined by an X-ray crystal structure analysis as SC,RIr,E.
Datum: 11.08.2016

Preparation, Characterization, Redox, and Photoinduced Electron-Transfer Properties of the NIR-Absorbing N-Ferrocenyl-2-Pyridone BODIPYs

Mono- and di-(N-ferrocenyl-2-pyridone)-containing BODIPYs were prepared using a set of ferrocene-enamine cyclization reactions. The target compounds were characterized by UV-Vis, NMR, and mass spectrometry, while their redox properties were probed by the electrochemical, spectroelectrochemical, and chemical oxidation methods. Redox properties of the di(ferrocenyl)-containing BODIPY suggestive of lack of the electronic coupling between two ferrocene groups. Oxidation of the ferrocene(s) in the target BODIPYs results in their observable fluorescence, while transient absorption spectroscopy data indicative of the fast electron-transfer from ferrocene donor to the photoexcited BODIPY acceptor. Density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to elucidate electronic structures of the organometallic BODIPYs and confirm the presence of the low-energy metal-to-ligand charge-transfer states in the NIR region.
Datum: 11.08.2016

Synthesis and reactivity of ferrocenyl allylamine derivatives.

((2-ferrocenylvinyl)methyl)dimethylamine 2 was obtained in good yields with perfect regio and reaction of dimethylmethylideneammonium salts on vinylferrocene. After methylation of amine 2, ((2-ferrocenylvinyl)methyl)trimethylammonium 4 was obtained in high yields and used to transfer ferrocene-containing allyl group on various amines. By controlling reaction conditions, various linear and branched ferrocenyl allylamines could be obtained with good yields and selectivities. When anilines were used as substrates against ammonium 4, compounds from Friedel-Crafts reaction with a complete regioselectivty for the para position were also obtained.
Datum: 11.08.2016

Prolonging the emissive lifetimes of new copper (I) complexes with 3MLCT and 3(-*) state equilibrium: a fluorene moiety used as "energy reservoir"

Two Cu(I) complexes, [Cu(imPhen)(POP)]PF6 (1), and [Cu(Flu-imPhen)(POP)]PF6 (2) (imPhen=1H-imidazo[4,5-f][1,10]phenanthroline, Ful-imPhen=2-(9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, POP=bis[2-diphenylphosphino]-phenyl)ether) have been synthesized and characterized. The weak MLCT absorption band at 401 nm with a relatively lower molar extinction coefficient (=3170 M-1 cm-1) was observed for 1. In constrast, 2 displayed the higher MLCT absorption band at 405 nm( =5400 M-1 cm-1) by the incorporation of a fluorene group to imPhen ring. 1 and 2 exhibited the similar emission wavelength and quantum yield (em=564 nm, =11.2% for 1 and em=568 nm, =9.0% for 2), however, the excited state lifetime of 2 (=51.2 µs) was almost four times longer than that of 1 (=13.8 µs). The prolonged luminescent lifetime of 2 was rationalized by the reversible energy transfer between the 3MLCT state of the Cu atom center and the 3(-*) state of fluorene moiety. To the best of our knowledge, a fluorene group is firstly used as the triplet energy reservoir to extend the excited state lifetime of an emissive 3MLCT state of the Cu(I)complexes.
Datum: 11.08.2016

The diphosphorus complex [Cp2Mo2(CO)4(eta2-P2)] as a building block for the synthesis of novel mixed-hybrid coordination polymers

The three component reaction of the tetrahedral diphosphorus complex [Cp2Mo2(CO)4(2-P2)] (1), with Ag[BF4] (2) in the presence of 2,2'bipyrimidine (3) leads to the formation of two novel two-dimensional networks (4 and 5). Compound 4 is a new two-dimensional organometallic-organic hybrid polymer, while derivative 5 represents a unique two-dimensional organometallic-inorganic-organic hybrid polymer. These results show the possibility to synthesis a new class of coordination polymers which could be obtained from two component reactions with organic molecules in addition of metal ions.
Datum: 11.08.2016

Superparamagnetic core-shell metal-organic framework Fe3O4/Cu3(BTC)2 microspheres and their catalytic activities for the aerobic oxidation of alcohols and olefins

Core-shell structured Fe3O4/Cu3(BTC)2 (BTC = 1, 3, 5-benzenetricarboxylate) microspheres were successfully synthesized by coating the metal-organic frameworks on polyacrylic acid (PAA) functionalized Fe3O4 microspheres with layer-by-layer assembly method. The MOF composite exhibits excellent catalytic activities in the aerobic oxidation of alcohols and epoxidation of olefins due to the porosity of MOFs and large amount of readily accessible Cu2+. Furthermore, the catalyst can be easily segregated from the catalytic system using an external magnetic field due to its high magnetization. The heterogeneous catalyst displays good reusability and shows extensive applicability in the aerobic oxidation of alcohols and epoxidation of olefins.
Datum: 11.08.2016

Vanadium Complexes Derived from Acetyl Pyrazolone and Hydrazides: Structure, Reactivity, Peroxidase Mimicry and Efficient Catalytic Activity for the Oxidation of 1-Phenylethanol

Schiff bases obtained from the condensation of acetylpyrazolone (H2ap) with benzoyl hydrazide (bhz), furoyl hydrazide (fah), nicotinoyl hydrazide (nah) and isonicotinoyl hydrazide (inh) [H2ap-bhz (I), H2ap-fah (II) H2ap-nah, (III) and H2ap-inh (IV)], sharing a ONO donor set, upon reaction with [VIVO(acac)2] lead to the formation of [VIVO(ap-bhz)(H2O)] (1), [VIVO(ap-fah)(H2O)] (2), [VIVO(ap-nah)(H2O)] (3) and [VIVO(ap-inh)(H2O)] (4), respectively. These complexes slowly convert to monooxidovanadium(V) complexes [VVO(ap-bhz)(OMe)(MeOH)] (11), [VVO(ap-fah)(OMe)(MeOH)] (12), [VVO(ap-nah)(OMe)(MeOH)] (13) and [VVO(ap-inh)(OMe)(MeOH)] (14) in methanol. The reaction of aqueous K[H2VVO4] with the corresponding potassium salt of the ligands at neutral pH gives dioxidovanadium(V) complexes, K(H2O)[VVO2(ap-bhz)] (5), K(H2O)0.5[VVO2(ap-fah)] (6), [VVO2(Hap-nah)] (9) and [VVO2(Hap-nah)] (10). Acidification of solutions of 5 and 6 affords the neutral complexes [VVO2(Hap-bhz)] (7) and [VVO2(Hap-fah)] (8), respectively. All complexes were characterized by various spectroscopic techniques: FT-IR, UV/Visible, EPR, NMR (1H, 13C and 51V); elemental analysis, thermal studies, cyclic voltammetry (CV) and single-crystal X-ray analysis. X-ray diffraction studies of complexes 6, 7, 9–12 confirm the ligand's coordination to the metal centre through enolic oxygen (of pyrazolone), azomethine nitrogen and enolic oxygen (hydrazide) atoms. The reactivity of the complexes and their catalytic potential was screened towards their peroxidase mimetic activity in the oxidation of pyragallol in aqueous media with H2O2 as oxidant, showing high activity under mild conditions. They were also tested in the catalytic oxidation of 1-phenylethanol with H2O2 that yields acetophenone as main product. Parameters such as catalyst and oxidant amount, time, temperature, and solvent effects were optimised for maximum oxidation of 1-phenylethanol. The complexes show excellent catalytic activity towards oxidation of 1-phenylethanol being structural and functional models of the vanadate-dependent haloperoxidases. The synthesis and reactivity of vanadium complexes, their abilities to mimic peroxidases and efficient catalytic activity for the oxidation of 1-phenylethanol are reported.
Datum: 11.08.2016

Tellurites of Hexavalent Uranium: First Observation of Polymerized (UO4)2– Tetraoxido Cores

Two novel Ca2(UO3)(TeO3)2 (1) and K2(UO2)2O2(TeO3) (2) uranyl tellurites were obtained from telluric acid, used as a starting reagent for both compounds. In 1, the tetraoxido core is coordinated by TeO3 groups and UO4 squares polymerize into [UO3] chains. The tetraoxido core coordination modes in compound 1 are unique. New layered ⋡2[(UO2)2(TeO3)O2]2– topology is observed for 2. Both of the compounds were studied by the means of high-temperature X-ray diffraction. The thermal decomposition of 1 and 2 is different and leads to formation of uranate compounds.Two novel Ca2(UO3)(TeO3)2 (1) and K2(UO2)2O2(TeO3) (2) uranyl tellurites were obtained from telluric acid. In 1, the tetraoxido core is coordinated by TeO3 groups and (UO4) squares polymerize into [UO3] chains. The tetraoxido core coordination modes in 1 are unique. A new layered ⋡2[(UO2)2(TeO3)O2]2– topology is observed for 2. Both compounds were studied by the means of high-temperature X-ray diffraction.
Datum: 11.08.2016

Implications of Guanidine Substitution on Copper Complexes as Entatic-State Models

The guanidine–quinoline ligand dimethylethyleneguanidinoquinoline (DMEGqu) is able to stabilise bis(chelate) copper complexes in an intermediate geometry between tetrahedral and square-planar environments. The structures of the obtained complexes model the entatic state and have been investigated in solid state by single-crystal X-ray diffraction and in the solid state and in solution by X-ray absorption spectroscopy. The dimethylethyleneguanidine (DMEG) unit of the DMEGqu ligand displays a smaller steric encumbrance than the tetramethylguanidine (TMG) counterpart; this allows slightly larger structural changes upon oxidation than those for the TMG counterparts. Moreover, triflate coordination was possible for the CuII DMEG complexes. DFT analyses revealed that good structural and optical descriptions are possible through the use of the hybrid functionals B3LYP and TPSSh in combination with the triple-zeta basis set def2-TZVP and the inclusion of empirical dispersion with Becke–Johnson damping and a suitable solvent model. The orbital analysis gives insights into the electronic structure of the complexes and their charge-transfer behaviour.A series of guanidine–quinoline copper complexes reveals that subtle influences such as the change in guanidine substitution have a large impact on the coordination distortion between tetrahedral and square-planar environments and the role of these complexes as entatic-state models.
Datum: 11.08.2016

Synthesis of AuI- and AuIII-Bis(NHC) Complexes: Ligand Influence on Oxidative Addition to AuI Species

The oxidation chemistry of a range of AuI-bis(NHC) (NHC = N-heterocyclic carbene) complexes with hypervalent iodine(III) oxidants has been explored. AuI-bis(NHC) precursors have been synthesised by treatment of the corresponding [Au(NHC)Cl] derivatives with imidazol(idin)ium salts in the presence of K2CO3. The reactivity of the AuI complexes towards PhICl2 has revealed an influence of the nature of the NHC ligands present in the complex on the outcome of the oxidation reaction: small and more strongly electron-donating NHC ligands favoured the formation of a AuIII species. On the basis of these results, a AuI complex bearing two 1-butyl-3-methylimidazol-2-ylidene (BMIM) ligands has been synthesised. This complex reacted with PhICl2 and also – for the first time in Au-NHC systems – with PhI(OAc)2 and PhI(OAcF)2 (OAcF = trifluoroacetate), affording stable AuIII-(NHC)2 complexes bearing acetate ligands.The oxidation chemistry of a range of AuI-bis(NHC) (NHC = N-heterocyclic carbene) complexes with hypervalent iodine(III) oxidants has been explored. The reactivity of the AuI complexes towards PhICl2 has revealed an influence of the nature of the NHC ligands present in the complex on the outcome of the oxidation reaction.
Datum: 11.08.2016

Reactivity of an NHC-Stabilized Silylene towards Lewis Acids and Lewis Bases

The reactivity of N-heterocyclic carbene stabilized (NHC-stabilized) aminochlorosilylene ArN(SiMe3)Si(IiPr)Cl (1, Ar = 2,6-iPr2C6H3, IiPr = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) with selected Lewis acids and Lewis bases is described. Treatment of 1 with BH3·THF yielded 1·BH3 (2) quantitatively. Compound 2 is a rare example of an air-insensitive silylene–borane adduct showing both acidic and basic properties of chlorosilylene in a single molecule. Crystals of 1–(CH2)3CH2OB(C6F5)3 (3) were obtained from the reaction of 1 with B(C6F5)3 in THF. For the first time, a frustrated Lewis pair (FLP) composed of a silylene and a substituted borane was observed to activate small molecules. Reaction of 1 with IMe4 (IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) at room temperature afforded silylene ArN(SiMe3)Si(IMe4)Cl (4), which represents a rare example of an NHC-stabilized silylene synthesized through ligand exchange.The reaction of N-heterocyclic carbene stabilized (NHC-stabilized) aminochlorosilylene ArN(SiMe3)Si(IiPr)Cl (1) with BH3·THF yielded silylene–borane adduct 2 quantitatively. In addition, compound 1 reacted with IMe4 to afford ArN(SiMe3)Si(IMe4)Cl (4), which represents a rare example of an NHC-stabilized silylene synthesized through ligand exchange.
Datum: 11.08.2016

New and Improved Syntheses of 1,2-Disubstituted Ferrocenes

1,2-Disubstituted ferrocenes, in particular 1,2-dihaloferrocenes, are important starting materials. Here we describe new and significantly improved syntheses of some 1,2-disubstituted ferrocenes providing these compounds in high yields. These include 1,2-dibromo- and 1,2-diiodoferrocene as well as 1-bromo-2-iodoferrocene, and 1-bromo-2-fluoroferrocene. DFT calculations show that 1,2-dihaloferrocenes do not differ much in their HOMO energies, however, their LUMO energies and thus the HOMO-LUMO gaps correlate with the sum of the halogen electronegativities. In addition, a synthesis of the rather sensitive 2-aminoferrocenecarboxylic acid, the ferrocene analogue of anthranilic acid, is presented, which starts from ferrocene-1,2-dicarboxylic acid. However, 2-aminoferrocenecarboxylic acid rapidly decomposed and thus could not be properly characterized. Ferrocene-1,2-dicarboxylic acid anhydride serves as the starting material for preliminary photochemical decarbonylation/decarboxylation experiments resulting in 1,2-dideuterioferrocene when carried out in d8-toluene.
Datum: 10.08.2016

Gold(I)-Catalyzed Reaction of Ferrocene and Propargylic Esters: Synthesis of Functionalized Ferrocene Derivatives

The reaction of propargylic esters with ferrocene in the presence of gold catalysts provided ferrocene derivatives containing a functionalized vinyl moiety. This ferrocene C-H bond functionalization takes place with complete regio- and stereoselectivity. The reaction is proposed to proceed through an electrophilic substitution in which a vinylgold carbene intermediate arising from a 1,2-rearrangement of the starting propargylic ester would behave as the electrophilic counterpart.
Datum: 09.08.2016

A Halogen Bonding 1,3-Disubstituted Ferrocene Receptor for Selective Recognition and Redox Sensing of Azide

A neutral redox-active acyclic halogen bonding (XB) receptor with a ferrocene core functionalised at the 1,3-positions of a cyclopentadienyl ring with iodotriazole motifs is prepared. Owing to favourable host-guest size-complementarity, the receptor was found to be selective for azide over a diverse range of anions with different geometries. Voltammetric studies revealed the unique ability of the XB ferrocene receptor to selectively sense azide via a significant cathodic shift of its ferrocene/ferrocenium redox couple. Notably, much weaker binding of azide was observed for the hydrogen bonding 1,3-bis-prototriazole ferrocene receptor analogue, which also displayed a poorer electrochemical response suggesting that halogen bonding interactions play crucial roles in the selective binding and sensing of azide.
Datum: 09.08.2016

Asymmetrical 1,3-bis-(heteroazolyl)benzene platinum complexes with tunable second-order nonlinear optical properties

A series of cyclometalated platinum(II) complexes bearing asymmetrical 1,3-bis-(heteroazolyl)benzene ligands, as chloro or phenylacetylene derivatives, have been synthetized and characterized. The N^C^N proligands, (benzoxazolyl) (benzothiazolyl)benzene in complex 1 and related compounds, and (benzoxazolyl)(benzimidazolyl)benzene in complex 2, have been synthesized by a two-step procedure including a Pd-catalysed C-H bond activation reaction. Electronic absorption, luminescence and second-order nonlinear optical properties of the novel complexes have been investigated experimentally and theoretically (TD-DFT) calculations, and compared to that of the known 1,3-bis-(benzoxazolyl)benzene platinum complex for which the nonlinear optical response have been studied for the first time. All complexes exhibit green luminescence in dichloromethane solution at room temperature, and the nature of the heteroazolyl ligand and/or the substituent at the central phenyl ring has no significant impact on the emission signatures. In contrast, the functionalization of the terdentate ligands and the nature of the ancillary ligand (chloride or phenylacetylide) allow modulating the nonlinear optical activity.
Datum: 09.08.2016

Band Gaps and Photocurrent Responses of Bulk and Thin-film Coordination Polymers Based on 3,6-di(1H-imidazol-1-yl)-9H-carbazole

Based on a novel rigid N-donor, 3,6-di(1H-imidazol-1-yl)-9H-carbazole (L), two CPs formulated as CdL(L1)3DMF (H2L1 = 4,4'-carbonyldibenzoic acid, DMF = N,N'-dimethylformamide) (1) and Cu2L2(SO4) (2) have been solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. CP 1 exhibits a two-dimensional (2D) structure, and CP 2 shows a one-dimensional (1D) chain. The two CPs exhibit different quasi-reversible redox properties and they possess very weak photoluminescence properties. Density functional theory (DFT) calculation and experiment results show that CP 1 has wider band gap than CP 2. Notably, CP 2 produces higher photocurrent density than CP 1 upon the visible light illumination, which is also in agreement with their Nyquist plots and MottSchottky curves. The thin-film CP 1 has been obtained via physical exfoliation in methanol, and it shows more active electrochemical behavior and enhanced photoresponse than bulk CP 1.
Datum: 09.08.2016

Eu2(CN2)3 and KEu[Si(CN2)4]: Missing Members of the Rare Earth Metal Carbodiimide and Tetracyanamidosilicate Series

Europium(III) compounds with the compositions Eu2(CN2)3 and KEu[Si(CN2)4] were prepared by solid-state metathesis reactions. The europium(III) carbodiimide was prepared by the reaction of EuF3 and Li2CN2, while the europium(III) tetracyanamidosilicate was prepared from EuF3, K2SiF6, and Li2CN2. Their crystal structures were refined from powder XRD data with space groups C2/m for Eu2(CN2)3 and P21212 for KEu[Si(CN2)4]. Luminescence spectra of Eu2(CN2)3 and KEu[Si(CN2)4] as well as nonlinear optical properties of KEu[Si(CN2)4] are reported. The two synthesized compounds are the missing members of the rare earth metal carbodiimide and tetracyanamidosilicate series. Eu2(CN2)3 and KEu[Si(CN2)4] were prepared by solid-state metathesis reactions and structurally characterized. These Eu3+ compounds are the missing members of the RE carbodiimide and RE tetracyanamidosilicate series. Both compounds show narrow-line red emission originating from 5D0  7FJ transitions of Eu3+. For KEu[Si(CN2)4] the frequency-doubling effect was observed.
Datum: 09.08.2016

Reaction of [RuNO(NO2)4OH]2– with Sulfamic Acid as a Pathway to Mixed Nitro Pyridine Ruthenium Nitrosyl Complexes

The transformations of [RuNO(NO2)4OH]2– during sequential treatment with sulfamic acid and pyridine have been investigated by 15N NMR spectroscopy. Depending on the initial molar ratio of Ru/NH2SO3H, the first stage of the reaction at room temperature in an aqueous solution proceeded with stoichiometric removal of one or two NO2 ligands and may be accompanied by ligand redistribution and partial isomerization NO2/ONO. Further treatment with pyridine resulted in the replacement of labile ligands (H2O, SO4) and the formation of mixed nitro pyridine complexes of ruthenium nitrosyl. Mixed nitrito-N-nitrito-O complexes PyH[RuNO(NO2)2(ONO)Py(OH)] and OC-6-34-[RuNO(NO2)(ONO)Py2OH] as well as the dimeric ruthenium complex with µ-bridging oxo groups NH4[Ru(NO)Py3(µ-O)]2(PF6)3 were separated as solids and structurally characterized. The photochemical isomerization (445 nm, 9 K) of Ru–NO with the formation of metastable isonitrosyl complexes was found for all the prepared compounds; the population of the metastable state did not exceed 20 %. The transformations of [RuNO(NO2)4OH]2– during sequential treatment with sulfamic acid and pyridine have been investigated by 15N NMR spectroscopy. The structures of the final mixed amine-nitrito-N(nitrito-O) complexes have been determined by X-ray diffraction analysis.
Datum: 09.08.2016

Aroylphosphanes: Base-Free Synthesis and Their Coordination Chemistry with Platinum-Group Metals

A series of aroylphosphanes have been prepared in good yield by base-free condensation of the respective aroyl chloride and HPPh2. Alongside the cyclophane m-{-C(O)-C6H4(C(O)PMe)}2 (1), the IR spectroscopic signatures of C6H4R{C(O)PPh2} (R = 3-Me 2, 3-CH2Cl 3, 4-CO2Me 4, 4-CN 5) and the bis(aroylphosphanes) C6H4{2,6-C(O)PPh2}2 (6) and C6H3N{2,6-C(O)PPh2}2 (7) are consistent with a manifestation of “phosphomide” character; however, weight of evidence suggests negligible contribution from this canonical form. Comparison is drawn to the structurally characterised O=P(C6H5Me-2)3 (8) in which the lone pair is sequestered. The coordination of 2–5 to rhodium(I), palladium(II) and platinum(II) is described, affording rare examples of aroylphosphane complexes of the platinum-group metals.The facile base-free synthesis of a range of aroylphosphanes is described. Consideration of their spectroscopic features, alongside structural data for related systems, implies negligible “phosphomide” character. Their coordination chemistry toward platinum-group metals is described, providing rare examples of this type of complex.
Datum: 09.08.2016

Alternative Synthetic Route to Potassium Octacyanidoniobate(IV) and Its Molybdenum Congener

Octacyanidometallates have been proven to be very useful molecular building blocks for the construction of various molecular materials with a strong emphasis on magnetic properties. However, their availability is still limited due to the preparation difficulties. Existing methods for their preparation consume large amounts of cyanide and require prolonged time for the synthesis. In this contribution novel synthetic routes for octacyanidoniobate(IV) and octacyanidomolybdate(IV) using NbCl4(THF)2 and MoCl5, respectively, as starting materials are reported. The synthesis of both complexes are significantly improved in terms of simplicity, preparation time, yield and purity.A novel alternative synthetic route for octacyanidoniobate(IV) and octacyanidomolybdate(IV) are reported. The preparation of both complexes is significantly improved in terms of simplicity, preparation time, yield and purity.
Datum: 09.08.2016

Single-Ion Magnets Based on Mononuclear Cobalt (II) Complexes with Sulfadiazine.

The already reported monomeric complex Co(SDZ)2Bpy (1) and the novel ternary complex Co(SDZ)2(6MQ)2 (2) (SDZ = sulfadiazine; Bpy = 2,2-bipyridine and 6MQ = 6-methoxyquinoline) have been synthesized in order to study their magnetic properties. X-ray diffraction method indicates that in both compounds the SDZ acts as a bidentate ligand coordinating through the sulfonamide and the pyrimidinic N-atoms giving raise a CoN6 coordination sphere. The complexes have been characterized based on elemental analyses, FTIR, UV-Visible spectroscopy and thermogravimetric analysis (TGA, only for 2). Both compounds, 1 and 2, have been characterized magnetically and they show slow relaxation of the magnetization below 9 and 6 K, respectively.
Datum: 08.08.2016

Diphosphorus Ligands Containing a P-Stereogenic Phosphane and a Chiral Phosphite or Phosphorodiamidite – Evaluation in Pd-Catalysed Asymmetric Allylic Substitution Reactions

The synthesis of 14 new optically pure C1-symmetric phosphane–phosphinite (1–4), phosphane–phosphite (5–9) and phosphane–phosphorodiamidite (10–14) ligands is reported. The ligands were prepared through the condensation of (2-hydroxyphenyl)phenylphosphanes PPh(2-PhOH)R (R = Me, tBu and Ph) with chlorodiisopropylphosphane (1 and 2), chlorodiphenylphosphane (3 and 4), the chlorodioxaphosphepine derived from both enantiomers of 1,1′-bi-2-naphthol (5–9) and the chlorodiazaphosphepine derived from both enantiomers of N,N′-dimethyl-1,1′-binaphthyl-2,2′-diamine (10–14) in the presence of a base. With these ligands, cationic Pd complexes of the type [Pd(η3-C4H7)(PP′)]PF6 (Pd1–Pd14) were obtained and characterised; the crystal structures of Pd1, Pd2 and Pd13 were obtained. In solution, the complexes are present as mixtures of two diastereomers because of the lack of symmetry of the ligand and the presence of the methallyl group. The Pd complexes catalyse the allylic alkylation with dimethyl malonate and the amination with benzylamine of the model substrate rac-3-acetoxy-1,3-diphenyl-1-propene (I). For the alkylation, full conversions and good enantioselectivities (up to 96 % ee with Pd14) were observed.A series of C1-symmetric diphosphorus ligands containing a P-stereogenic phosphane moiety are synthetized and characterized. The derived π-methallyl Pd complexes are used in catalytic allylic substitutions and provide good conversions and enantioselectivities.
Datum: 06.08.2016

Ligands with Two Different Binding Sites and O2 Reactivity of their Copper(I) Complexes

The synthesis of two new unsymmetric dinucleating ligand systems, L1, combining a bidentate binding site with a tridentate binding site linked through a dibenzofuran spacer, and L2, with two tridentate binding sites bridged by an ethylene spacer, is reported. The ligands L1 and L2 were used for the preparation of the dicopper(I) complexes [Cu2(L1)(NCCH3)3](X)2, {[Cu2(L1)Cl2]}n and [Cu2(L2)(NCCH3)2](Y)2 (X = PF6, BF4, OTf; Y = ClO4, PF6, BF4), in which the two respective copper ions possess two different coordination environments. All complexes reacted with O2, but in the case of the L1 series, no primary O2 adduct could be identified by UV/Vis spectroscopy. Reaction of the [Cu2(L2)(NCCH3)2](Y)2 complexes with pure oxygen led to the formation of an O2 adduct that proved rather unstable.Seven dicopper(I) complexes are accessed from two unsymmetric dinucleating ligand systems. The complexes react with dioxygen, and in the case of the L2 series, a sensitive O2 adduct is observed.
Datum: 06.08.2016

Formation of a Radical Tricationic Tetraborane(4) by Hydride Abstraction from sp3–sp3-Hybridized Diboranes

The formation, electronic structure, and reactivity of the recently-reported radical tricationic tetraborane [B4(hpp)4]·3+ (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), which features a planar rhomboid B4 unit and bridging bicyclic guanidinate (hpp) substituents, is reported. New experiments show that the tetraborane could be synthesized by hydride abstraction either in a very fast reaction from the electron-rich sp3–sp3-hybridized diborane [HB(hpp)]2, or in a very slow reaction from the cationic, less electron-rich sp3–sp3-hybridized diborane [HB(hpp)2BPCy3]+. The results argue for an electron-transfer in the rate-determining step of a complex reaction sequence. Quantum chemical calculations highlight the role of the hpp substituents for the stabilization of the radical tricationic tetraborane [B4(hpp)4]·3+. Further analysis shows that [B4(hpp)4]·3+ is highly reactive, and especially a very strong electrophile. This reactivity makes the compound very interesting because boron atoms in such a low oxidation state (<2) are expected to be strong nucleophiles. The formation, electronic structure, and reactivity of the recently-reported radical tricationic tetraborane [B4(hpp)4]·3+ (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate), which features a planar rhomboid B4 unit and bridging bicyclic guanidinate (hpp) substituents, is reported. The high reactivity as a very strong electrophile of the compound very interesting because boron atoms in such a low oxidation state (<2) are expected to be strong nucleophiles.
Datum: 06.08.2016

Discrimination of Octahedral versus Trigonal Bipyramidal Coordination Geometries of Homogeneous TiIV, VV, and MoVI Amino Triphenolate Complexes through Nitroxyl Radical Units

A new stable radical-containing ligand and the corresponding VV, TiIV, and MoVI complexes have been synthesized and studied by electron paramagnetic resonance (EPR) spectroscopy. To achieve this goal, a novel strategy for the post-derivatization of a triphenolamine (TPA) ligand has been developed. This has allowed the effective embedding of three TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) radicals in the corresponding metal complexes. In these systems, dipolar interactions among the organic radicals are strongly dependent on the geometry assumed in solution: a |Δms| = 2 transition is observed when the geometry of the complexes is octahedral, whereas no signal is detected with trigonal bipyramidal geometries.A new stable radical-containing ligand and the corresponding VV, TiIV, and MoVI complexes have been synthesized and studied by electron paramagnetic resonance (EPR) spectroscopy. In these systems, dipolar interactions among the organic radicals are strongly dependent on the geometry assumed in solution.
Datum: 06.08.2016

Magnetic Bistability in Macrocycle-Based FeII Spin-Crossover Complexes: Counter Ion and Solvent Effects

Two new iron(II) complexes of formula [Fe(L2)](tcm)2·2H2O (1) and [Fe(L2)][Ni(CN)4]·H2O (2) {L2 = 1,8-bis(2′-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane; tcm– = [C(CN)3]– = tricyanomethanide anion} have been synthesized and characterized by X-ray diffraction and magnetic measurements and compared with the previously described compound of the same series [Fe(L2)](BF4)2·H2O (3). The crystal structures of the three compounds show discrete iron(II) complexes in which the FeII ions adopt distorted FeN6 octahedral geometries. A hydrogen-bonding network involving the water molecules and the different counter ions, tcm– in 1 and [Ni(CN)4]2– in 2, leads to chains for both compounds whereas compound 3 reveals no significant intermolecular contacts. For 1, the magnetic measurements show an abrupt and incomplete high-spinlow-spin (HSLS) spin transition (ST) with a hysteresis of 9 K (T1/2down = 136 K; T1/2up = 145 K) that is also optically observed. Compound 2 presents slightly weaker intermolecular contacts and shows an abrupt ST at 85 K without hysteretic behaviour. Finally, compound 3, in which the FeII complex is well isolated, exhibits a gradual spin transition centred at 150 K. Detailed X-ray diffraction studies performed at various temperatures (293–120 K) show strong modifications of the iron coordination sphere in 1 and 3, in agreement with the presence of a ST in this temperature range in both complexes.A new series of FeII spin-crossover complexes based on an N-functionalized macrocycle ligand have been prepared and fully characterized. One exhibits magnetic bistability with a 9 K wide hysteresis loop (136–145 K) and the other two show either an abrupt (T1/2 = 83 K) or gradual (T1/2 = 150 K) transition without hysteresis. The different behaviour can be explained by intermolecular interactions.
Datum: 06.08.2016

Bis(N-methylimidazole)-Substituted Neutral Phthalocyanines {MIII(MeIm)2(Pc)·3–}0 (M = Al, Ga) Containing Radical Trianionic Phthalocyanine Macrocycles

Reduction of aluminium(III) and gallium(III) chloride phthalocyanines (Pc) in the presence of N-methylimidazole (MeIm) by sodium fluorenone ketyl allows the dissolution of phthalocyanines. Slow mixing with n-hexane crystallizes formally neutral compounds [AlIII(MeIm)2(Pc)·3–]0·MeIm (1) and [GaIII(MeIm)2(Pc)·3–]0·2C6H4Cl2 (2), which contain radical trianionic phthalocyanine {Pc·3–} macrocycles. The formation of Pc·3– is confirmed by the appearance of new bands in the NIR range with maxima at 999 (1) and 994 nm (2) and a blueshift of both the Soret and Q-bands of the phthalocyanines. The phthalocyanine macrocycles in 1 and 2 are planar with the central metal atoms positioned exactly in the Pc plane. The average lengths of the M–N(Pc) and M–N(MeIm) bonds in 1 are 1.956(3) and 2.055(2) Å, and they are elongated up to 1.987(1) and 2.161(1) Å, respectively, in 2. The formation of the 19π-electron system of Pc·3– results in partial disruption of the aromaticity with alternation of shorter and longer C–N(imine) bonds belonging to two oppositely located isoindole units in 1 and 2. The presence of unpaired spins on the macrocycles is justified by intense Lorentzian EPR signals with g = 2.0028 and linewidth (ΔH) = 0.648 mT in 1 and g = 2.0011 and ΔH = 0.551 mT in 2 at room temperature. The effective magnetic moment of 2 of 1.65 µB at 300 K indicates the contribution of one non-interacting S = 1/2 spin per formula unit, which is weakly antiferromagnetically coupled with a Weiss temperature of –6 K. Weak coupling can be explained by weak π–π interaction between the Pc·3– macrocycles in 2.Reduction of AlIIICl(Pc2–) and GaIIICl(Pc2–) (Pc = phthalocyanine) in the presence of N-methylimidazole (MeIm) by sodium fluorenone ketyl gives neutral compounds [AlIII(MeIm)2(Pc·3–)]0·MeIm (1) and [GaIII(MeIm)2(Pc·3–)]0·2C6H4Cl2 (2), containing radical trianionic Pc·3– species. The Pc·3– formation is confirmed by optical, structural and magnetic measurements. The unpaired spins show a weak antiferromagnetic coupling in 2.
Datum: 06.08.2016

Variation of Desolvation Behaviour in Two Isostructural Metal–Organic Frameworks Based on a Flexible, Racemic Bifunctional Organic Linker

A racemic mixture of the chiral ligand 4,4′-(1,2-dihydroxyethane-1,2-diyl)dibenzoic acid was used to prepare two isostructural metal–organic frameworks, CPO-49-Zn and CPO-49-Mn, which contain coordinated solvent molecules at the metal site. The compounds showed different behavior upon desolvation. The dissociation of the solvent molecule from the metal site leads to a single-crystal-to-single-crystal transformation. In CPO-49-Zn, a change of coordination geometry from trigonal bipyramidal to tetrahedral occurs at the zinc atom. In CPO-49-Mn, a rearrangement of coordination mode of a carboxylate group occurs instead, leading to a 4+1 coordination of the manganese cation in the form of a capped distorted tetrahedron. N2 gas adsorption confirms that both desolvated structures are permanently porous. The behavior of the compounds upon heating has also been studied using variable temperature powder X-ray diffraction. The presence of a coordinated solvent molecule in the as-synthesized structures indicates the possibility to access the metal cation with reactive substrates. Both materials were evaluated in the catalytic oxidation of styrene. CPO-49-Mn showed significantly higher conversion than the CPO-49-Zn material.Two new isostructural metal–organic frameworks based on Zn and Mn and a chiral organic linker were synthesized. Solvent removal leads to single-crystal-to-single-crystal transformation, which proceeds in different fashion for the two metals. The compounds also behave differently upon heating and in catalysis.
Datum: 06.08.2016

Reversible Redox Transformations of Bridging Sulfide Ligands within Bioctahedral Rhenium Cluster Anions

The present study provides new experimental data on the reactivity of sulfur-based ligands connected to Re atoms. It was recently discovered that oxidation of µ-S ligands within the bioctahedral [Re12CS14(µ-S)3(CN)6]6– cluster anion using H2O2 led to the formation of µ-SO2 and µ-SO3 products. This work is focused on the investigation of the opposite process – reduction of the [Re12CS14(µ-SO2)3(CN)6]6– anion to [Re12CS14(µ-S)3(CN)6]6– by sulfide ions in an aqueous medium under mild conditions. The reduction results in a slow change of the solution colour, making it possible to investigate in detail the intermediate products. Analysis of the reaction mixture by ESI mass spectrometry revealed that a series of cluster anions [Re12CS17On(CN)6]6– (n = 0–5) was generated during the process. This indicates stepwise chemical reduction of bridging SO2 ligands proceeding through the formation of µ-SO ligands. In this way, twelve-nuclear rhenium clusters demonstrate a unique, fully reversible redox cycle of their µ-bridging ligands, keeping the cluster core unchanged. Two mixed-ligand cluster anions, [Re12CS14(µ-SO2)2(µ-S)(CN)6]6– and [Re12CS14(µ-SO2)(µ-S)2(CN)6]6–, were found to be the major reaction intermediates. The former was crystallised with [Cu(NH3)5]2+ and [Cd(NH3)n]2+ ammine cations and investigated by single-crystal X-ray diffraction. To understand the electronic structure and charge distribution in [Re12CS17On(CN)6]6– cluster anions, DFT calculations were also carried out.Reduction of µ-SO2 ligands to µ-S within [Re12CS14(µ-L)3(CN)6]6– cluster anions takes place in aqueous solution containing S2–. The reduction proceeds through a variety of cluster anions containing µ-S, µ-SO and µ-SO2 ligands. In this way, twelve-nuclear rhenium clusters represent a unique example of reversible redox transformations of bridging ligands keeping the cluster core unchanged.
Datum: 05.08.2016

Peierls-Distorted Ru-Chains and Boron Dumbbells in Nb2RuB2 and Ta2RuB2 from First-Principles Calculations and Experiments

Nb2RuB2 and Ta2RuB2 phases were recently predicted by GGA-VASP structure optimization to crystallize in the Nb2OsB2-type structure. Although the Fe-based (Mo2FeB2 type) and Os-based (Nb2OsB2 type, superstructure variant of Mo2FeB2 type) analogues have been synthesized and characterized successfully, the Ru-based phases remained unknown. Crystal structure prediction of Nb2RuB2 and Ta2RuB2 phases, using an evolutionary algorithm, led to the AlMn2B2-type structure in contrast to the aforementioned optimization; however, phonon calculations showed that the Nb2OsB2-type phases are dynamically more stable than the AlMn2B2-type phases. A slightly modified synthetic strategy finally led to the successful preparation of the predicted phases. The extremely quick arc-melting procedure, under argon atmosphere, not only led to a quantitative amount of the phases but also to single crystals suitable for structure determination. Powder and single-crystal X-ray diffraction as well as EDX analysis of the metal ratio have confirmed the GGA-VASP structure optimization: Nb2RuB2 and Ta2RuB2 compounds indeed crystallize isotypically with Nb2OsB2 structure, a superstructure variant of Mo2FeB2 type, in which B-dumbbells and Peierls-distorted Ru-chains are found. Susceptibility measurements on a Ta2RuB2 single crystal reveal no superconducting transition down to 2 K, even though some features in the band structures of both phases, similar to those reported in superconducting NbRuB, hinted at possible superconductivity.Two methods to predict the structure of A2RuB2 (A = Nb, Ta) compounds led to two structure types, the AlMn2B2-type and Nb2OsB2-type for both compounds. Phonon calculations revealed that the former is dynamically unstable for A2RuB2, while the latter is stable. Single-crystal refinements confirmed Nb2OsB2-type structure and the presence of Peierls-distorted Ru-chains.
Datum: 05.08.2016

Ru(bpy)3[PF6]2 Complex with Rhodamine Unit: Synthesis, Photophysical Properties and Application in Acid-Controllable Triplet-Triplet Annihilation Upconversion

Ruthenium(II) trisbipyridine-rhodamine dyad was prepared for controlling of the triplet state properties with external stimuli (Acid). The rhodamine moiety is acid-responsive module and Ru(II) coordination center is responsible for triplet state formation upon photoexcitation. With steady-state UVvis absorption and luminescence spectra, electrochemical characterization, nanosecond/femtosecond transient absorption spectroscopy, we found that in the absence of acid, the dyad gives quenched 3MLCT triplet excited state (lifetime= 103.6 ns vs. 1.54 microseconds), due to the photo-induced electron transfer (PET) process. In the presence of acid, the rhodamine unit reversibly transformed from the spirolactam structure into the opened amide structure, thus with the PET inhibited, prolonged triplet state lifetime (5.70 microseconds) was resulted, and the T1 state is relocated to the rhodamine unit. This is the first time that the fundamental triplet excited state properties of Ru(II) complex, i.e. the triplet lifetime, and localization, have been simultaneously controlled. Intramolecular singlet-triplet energy transfer and triplet-triplet-energy-transfer (TTET, 3MLCT->3IL) were observed for the dyad with the femtosecond and nanosecond transient absorption spectra, respectively. The dyad was used for acid-controllable triplet-triplet annihilation upconversion.
Datum: 04.08.2016

Reversible Formation of a Cerium-Bound Terminal Hydride: Ce(C5Me4SiMe3)2(H)(thf)

The use of the bulky cyclopentadienyl ligand Cp' (Cp' = C5Me4SiMe3) to stabilize cerium hydrides has resulted in the preparation of two novel tuck-in complexes with C-H activated SiMe3 groups. Subsequent reaction of these with H2 in thf gives a rare lanthanide terminal hydride species Ce(Cp')2(H)(thf) which reversibly regenerates the tuck-in complex under sustained vacuum. This compound is only the second structurally characterized terminal cerium hydride. This new hydride is a catalyst in H/D exchange reactions between with both sp3-CH and sp2-CH bonds, and for the hydrogenation of unsaturated alkene bonds.
Datum: 04.08.2016

Iron and Ruthenium Alkynyl Complexes with 2-Fluorenyl Groups: Some Linear and Nonlinear Optical Absorption Properties

Four new mononuclear alkynyl complexes each featuring a terminal 2-fluorenyl group, namely Fe(η5-C5Me5)(CO)2[C≡C(2-C21H25)] (2), Ru(κ2-dppe)2Cl[C≡C(2-C21H25)] (3), Ru(κ2-dppe)2[C≡C(4-C6H4NO2)][C≡C(2-C21H25)] (4), and [Fe(η5-C5Me5)(κ2-dppe){C≡C(C5H4N)-CH2(2-C13H9)}][PF6] (5[PF6]), have been synthesized and characterized, and their redox, absorption, and emission properties have been studied. For the two ruthenium derivatives 3 and 4, these studies are complemented by spectroelectrochemical investigations, Z-scan measurements, and DFT calculations. Fluorimetric studies reveal that these compounds are poorly or not luminescent, and, when luminescent, that the detected weak luminescence most likely originates from a higher lying ligand-centred (LC) excited state presumably located on fluorene. Finally, the third-order nonlinear optical (NLO) properties of 3 and 4 are reported. It is shown that the bis-alkynyl complex 4 is significantly more active than 3 and that both compounds exhibit two-photon absorption (TPA) around 860–1050 nm, with TPA cross-sections above 350 GM. In addition, it is shown that both species should give rise to a marked switching of their cubic NLO properties in this spectral range upon oxidation.The linear and third-order nonlinear optical properties of a series of new 2-ethynylfluorene complexes are investigated and compared with those of known Fe(Cp*)(dppe) analogues. Among these, the bis-alkynyl RuII derivatives give rise to remarkably large and potentially redox-switchable apparent two-photon absorptions in the 700–750 nm wavelength range.
Datum: 02.08.2016

Rhodium and Iridium Fluorido and Bifluorido Complexes Derived from Peroxido Precursors

The rhodium and iridium fluorido bifluorido complexes trans-[Rh(4-C5F4N)(F)(FHF)(CNtBu)(PEt3)2] (1) and trans-[Ir(4-C5F4N)(F)(FHF)(CNtBu)(PiPr3)2] (2) have been synthesized by protonation of the peroxido complexes trans-[M(4-C5F4N)(O2)(CNtBu)(PR3)2] with an HF source (M = Rh, R = Et; M = Ir, R = iPr). Abstraction of the coordinated HF resulted in the formation of the difluorido compounds trans-[M(4-C5F4N)(F)2(CNtBu)(PR3)2] (4: M = Rh, R = Et; 5: M = Ir, R = iPr).The rhodium and iridium fluorido bifluorido complexes trans-[M(4-C5F4N)(F)(FHF)(CNtBu)(PR3)2] (M = Rh, R = Et; M = Ir, R = iPr) have been synthesized from the peroxido precursors by using HF sources. Abstraction of the coordinated HF by base gave the difluorido complexes trans-[M(4-C5F4N)(F)2(CNtBu)(PR3)2] (M = Rh, R = Et; M = Ir, R = iPr).
Datum: 29.07.2016

The Ethylhexanoate Route to Metal Oxide Nanocrystals: Synthesis of CoO Nanooctahedra from CoII 2-Ethylhexanoate

CoO nanocrystals were prepared by solvothermal processing of Co 2-ethylhexanoate in oleylamine at 250 °C. The obtained products, identified as CoO by X-ray diffraction, had an octahedral shape, as seen by transmission electron microscopy, reflecting the cubic symmetry of the CoO crystallographic phase. The materials were converted into the Co3O4 phase after heat treatment at 400 °C. The nanocrystal evolution was investigated by FTIR spectroscopy. It was concluded that weak oleylamine bonding to the nanocrystal surface during the synthesis step favored the exchange with 2-ethylhexanoato ligands, and that the interplay between the two ligands favored the kinetic control of the growth, resulting in the finally observed octahedral morphology. The Co3O4 phase obtained from the heat treatment at 400 °C was used to process chemoresistive sensors, which were able to detect ethanol under dry and humid conditions (0 and 50 % r.h. H2O at 25 °C) at low temperatures (100 °C).The solvothermal processing of Co 2-ethylhexanoate in oleylamine results in octahedral CoO nanocrystals induced by the rocksalt, cubic crystallographic phase of CoO. This result stems from the kinetic control over the nanocrystal growth resulting from the co-presence of 2-ethylhexanoato and oleylamine ligands during the synthesis.
Datum: 29.07.2016

A Dual-Characteristic Bidentate Ligand for a Ternary Mononuclear Europium(III) Molecular Complex – Synthesis, Photophysical, Electrochemical, and Theoretical Study

The new bipolar ligand 4-{1-(9,9-diethyl-9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl}-N,N-diphenylbenzenamine (Phen-Fl-TPA) and its β-diketonate EuIII complex have been designed, synthesized, characterized, and their photophysical and electrochemical properties have been investigated. The UV/Vis absorption and photoluminescence (PL) emission spectra of the Eu complex and Phen-Fl-TPA in solution as well as in the solid state and as thin films were recorded. The PL study indicated that the Eu complex emits narrow-band red emission with an appropriate International Commission on Illumination (CIE) color gamut. Moreover, it also confirmed the efficient energy transfer from the ligand to the Eu3+ ion. Time-dependent DFT (TD-DFT) calculations were performed for the ligand to determine the exact positions of the excited singlet and triplet energy levels. The EuIII complex shows a dominant pathway involving energy transfer between the ligand triplet level and the excited (5D0) level of the EuIII ion. In addition, the theoretically calculated UV/Vis spectrum of the ligand is similar to the experimental one. The Judd–Ofelt theory was applied to the emissive properties of the EuIII complex, and the lifetime was found to be 0.66 ms. The ground-state optimized ligand structure was a good match with the single-crystal structure. The photoluminescence quantum yield (PLQY) of Eu(TTA)3Phen-Fl-TPA (TTA = thenoyltrifluoroacetone) in solution was 34.1 %, and it possess a high thermal decomposition temperature (317 °C), as determined by differential scanning calorimetry/thermogravimetric analysis (DSC-TGA). Electrochemical analysis revealed highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels for the EuIII complex of 5.6 and 2.8 eV, respectively. Efficient energy transfer is observed from β-diketonate ligands as well as a triphenylamine–fluorene–phenanthroline-based bipolar ligand to EuIII ions, and the complex shows intense red emission (5D0–7F2) with 34.1 % photoluminescence quantum efficiency (PLQE).
Datum: 29.07.2016

Syntheses of [Pt6(CO)8(SnCl2)(SnCl3)4]4– and [Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)2]2– Platinum–Carbonyl Clusters Decorated by SnII Fragments

The reaction of [Pt6(CO)6(SnCl2)2(SnCl3)4]4– (1) with CO under atmospheric pressure resulted in the new [Pt6(CO)8(SnCl2)(SnCl3)4]4– (2) cluster by the addition of two CO ligands and the elimination of a stannylene SnCl2 group. In turn, 2 reacted with 2 equivalents of PPh3 under a CO atmosphere to afford [Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)2]2– (3) by elimination of two stannyl [SnCl3]– ligands. Conversely, the reaction of 2 with 2 equivalents of PPh3 under a N2 atmosphere resulted in a species tentatively formulated as [Pt6(CO)5(SnCl2)2(SnCl3)2(PPh3)2]2– (4–5CO) on the basis of 13C NMR, 31P NMR spectroscopy and ESI-MS studies. Compounds 2–4 were spectroscopically characterized by IR spectroscopy and multinuclear (13C and 31P) variable-temperature NMR spectroscopy. The crystal structures of 2 and 3 were determined by means of single-crystal X-ray diffraction, and their bonding was computationally investigated by DFT calculations. The possible structure of 4–5CO was predicted by means of DFT methods. The stepwise addition of CO and PPh3 to [Pt6(CO)6(SnCl2)2(SnCl3)4]4– results in the new [Pt6(CO)8(SnCl2)(SnCl3)4]4– and [Pt6(CO)8(SnCl2)(SnCl3)2(PPh3)2]2– bimetallic clusters. These clusters show perfect segregation of the two metals and are composed of a zero-valent Pt6 core decorated on the surface by CO, PPh3, SnCl2, and [SnCl3]– ligands.
Datum: 29.07.2016

Heterovalent 2EuII/4EuIII and Trivalent 5EuIII Clusters Assembled with a Macrocyclic Cyclen Derivative Ligand: Molecular Structures, Oxidation Stabilities, and Luminescence Properties

Two coordination complexes EuII2EuIII4(OH)4(bza)4L2 (1) and EuIII5(H2O)(OH)4(NO3)3(bza)4L (2) have been assembled with the tetrasubstituted cyclen ligand N,N′,N′′,N′′′-tetrakis(2-hydroxy-3-methoxy-5-methylbenzyl)-1,4,7,10-tetraazacyclododecane (H4L) and the auxiliary ligand benzoic acid (Hbza). Complex 2 is a pentanuclear EuIII cluster whereas complex 1 is a huge heterovalent 2EuII/4EuIII cluster in which two divalent europium ions are trapped within the macrocyclic cavities of the designed ligands L and are further isolated from the environment by peripheral phenyl rings and the tetrahedral 4EuIII cluster, which results in the enhanced oxidative stability of Eu2+. The luminescence of complex 1 was investigated and is discussed in comparison with the luminescence of ligand H4L and complex 2. Owing to the protection of Eu2+ by the macrocyclic ligands L, the heterovalent complex exhibits a strong broad emission band with a maximum at 533 nm as well as the characteristic sharp emissions of Eu3+. The broad emission is redshifted compared with that of ligand H4L and has been attributed to the Laporte-allowed 4f65d1  4f7 transition of Eu2+.Owing to the protection of Eu2+ by the macrocyclic ligand L, the heterovalent complex EuII2EuIII4(OH)4(bza)4L2 [1; Hbza = benzoic acid, H4L = N,N′,N′′,N′′′-tetrakis(2-hydroxy-3-methoxy-5-methylbenzyl)-1,4,7,10-tetraazacyclododecane] exhibits a strong broad emission band arising from Eu2+ as well as the characteristic sharp emissions of Eu3+.
Datum: 29.07.2016

Nano-Nonanuclear Mixed-Lanthanide Clusters [Eu9–xTbx] Featuring Tunable Dual Luminescence Properties

Five Tb3+/Eu3+ mixed nonanuclear clusters with the general formula [Eu9–xTbx(acac)16(µ3-OH)8(µ4-O)(µ4-OH)] ([Eu9–xTbx], x = 0.9–8.1, acac = acetylacetonate) were synthesized. Characterization by powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) highlight a near-perfect match between the amounts of Tb3+ and Eu3+ ions input in the reaction mixture and the amounts in the clusters. The luminescence properties of these [Eu9–xTbx] clusters were investigated thoroughly in the solid state, and a strong energy transfer from the Tb3+ to Eu3+ emitters was evidenced. Thus, these nano-nonanuclear 4f clusters, which can be viewed as square pyramids that share one top, exhibit dual luminescence that can be adjusted by controlling the ratio of the lanthanide ions within the crystal architecture. New mixed [Eu9–xTbx] nanoclusters exhibit adjustable dual luminescence with strong TbIII to EuIII energy transfer through the fine control of the amounts of the lanthanide ions within the crystal structure.
Datum: 28.07.2016

Difluoroborenium Cation Stabilized by Hexaphenyl-Carbodiphosphorane: A Concise Study on the Molecular and Electronic Structure of [(Ph3P)2C⇉BF2][BF4]

The reaction of hexaphenyl-carbodiphosphorane C(PPh3)2 (CDP, 1) with BF3·OEt2 provides the corresponding difluoroborenium cation [CDP–BF2]+ (2+) through fluoride abstraction. Advanced NMR spectroscopy methods, including 19F,31P HMQC; 31P,13C HMQC; 19F,1H HOESY; 19F NOESY; 31P,13C INEPT; and 1H, 31P, 19F, and 11B diffusion NMR measurements, were performed, and they revealed strong ion pairing of 2+ with the [BF4]– counterion in chloroform solution. Structural and computational studies showed strong donor–acceptor interactions, in which the σ and π lone pairs of electrons of C(PPh3)2 donate into the vacant orbitals of the [BF2]+ fragment. The C–B bond shows the highest interaction energy of 242.9 kcal mol–1 found for the corresponding carbodiphosphorane adducts.The reaction of C(PPh3)2 with BF3·OEt2 affords the difluoroborenium cation [CDP⇉BF2]+ (2+). Advanced NMR spectroscopy methods reveal strong ion pairing of 2+ with the [BF4]– counterion in solution. Structural and computational studies show strong donor–acceptor interactions in which both the σ and π lone pairs of electrons of C(PPh3)2 donate into the vacant orbitals of [BF2]+.
Datum: 28.07.2016

Innovative Concept of Designing Primary Explosives by IntroducingPolymers: Preparation and Investigation of {[Ca(CHZ)2](ClO4)2}n (CHZ = carbohydrazide)

A novel alkaline-earth metal perchlorate coordination polymer {[Ca(CHZ)2](ClO4)2}n (1, CHZ = carbohydrazide) was synthesized and characterized. The X-ray single-crystal diffraction results illustrate that the structure of the complex belongs to a tetragonal system, space group I-42m. Every Ca2+ ion is octa-coordinated with four CHZ groups. The CHZ group forms a tridentate coordination mode with different Ca2+ ions, leading to a coordination polymer structure. Therefore, the molecule is extended to a super 1D infinite polymer, and the configuration of the Ca2+ ion is a distorted dodecahedron. The DSC results show only one exothermal decomposition process with a peak temperature of 242.2 °C. The TG-DTG curves demonstrate a 58 % mass loss from 210–290 °C and that finally 18 % of the polymer remains. Experimental data show that the combustion heat is –6.41 MJ kg–1 and the enthalpy of formation is –610.9 kJ mol–1. Non-isothermal kinetic and thermodynamic parameters are obtained from Kissinger's method as well as Ozawa's method. The critical temperature of thermal explosion, ΔS≠, ΔH≠, and ΔG≠ are calculated as 234.7 °C, 134.1 J K–1 mol–1, 213.8 kJ mol–1, and 147.0 kJ mol–1, respectively. Additionally, the sensitivities towards impact and friction are assessed to be 0.5 J and 28 N from the relevant standard methods. Coordination polymers were introduced to primary explosives. The remarkable structure of “discrete MOFs” makes great sense in the design of thermal-stable molecules with proper sensitivities.
Datum: 28.07.2016

Square-Planar PtII versus Octahedral PtIV Halido Complexes: 195Pt NMR Explained by a Simple Empirical Approach

In this work, we show by a simple empirical approach that a linear relationship between observed 195Pt NMR frequencies and the overall sum of the ionic radii of the coordinated halido ligands [Σ(rh)] exists in square-planar PtII complexes of the type [PtXnY4–n]2– (1 ≤ n ≤ 4; X, Y = Cl, Br, I). Another finding was that such square-planar complexes could be empirically described as octahedral complexes, with the two lobes of the 5dz² orbital above and below the coordination plane acting as two pseudo-halido ligands, each showing a constant apparent radius of around 207 pm. According to our approach, the overall apparent radius of around 415 pm produces constant 195Pt NMR shielding for all [PtXnY4–n]2– complexes of about 10450 ppm. This result is 1) consistent with the theoretically calculated overall 5d shell lone-pair shielding observed in square-planar PtII with respect to octahedral PtIV complexes and 2) almost coincident with the already measured chemical shift anisotropy (CSA) of the K2[PtCl4] complex both in solution and in the solid state (single crystal).The 195Pt NMR chemical shifts of octahedral [PtXnY6–n]2–, square-planar [PtXnY4–n]2–, and pentacoordinate [PtXY(η2-C2H4)(2,9-Me2-1,10-phen)] (X, Y = halido) vary linearly with the overall sum of the ionic radii of the halido ligands. The square-planar PtII complexes may be treated empirically as octahedral complexes in which the filled 5dz² orbital acts as two pseudo-halido ligands.
Datum: 27.07.2016

Postsynthetic Modification of Zirconium Metal-Organic Frameworks

Metal-organic frameworks (MOFs) have been in the spotlight for a number of years due to their chemical and topological versatility. As MOF research has progressed, highly functionalised materials have become desirable for specific applications, and in many cases the limitations of direct synthesis have been realised. This has resulted in the search for alternative synthetic routes, with postsynthetic modification (PSM), a term used to collectively describe the functionalisation of pre-synthesised MOFs whilst maintaining their desired characteristics, becoming a topic of interest. Advances in the scope of reactions performed are reported regularly; however reactions requiring harsh conditions can result in degradation of the framework. Zirconium-based MOFs present high chemical, thermal and mechanical stabilities, offering wider opportunities for the scope of reaction conditions that can be tolerated, which has seen a number of successful examples reported. This microreview discusses pertinent examples of PSM resulting in enhanced properties for specific applications, alongside fundamental transformations, which are categorised broadly into covalent modifications, surface transformations, metalations, linker and metal exchange, and cluster modifications.The chemical and mechanical stabilities of zirconium metal-organic frameworks (MOFs) make them ideal platforms for postsynthetic modification. This microreview provides an overview of the various techniques for modification and the functionalities that can be incorporated into zirconium MOFs to facilitate different applications.
Datum: 27.07.2016

Structure and Magnetocaloric Effect of Two Kinds of Ln–MnII Heterometallic Coordination Polymers Produced by Fractional Crystallization

Two series of Ln–MnII heterometallic coordination polymers (HCPs), [Ln8Mn3(µ3-OH)8(IN)14Cl6(H2O)16]n(OH)2n·5nDMF·8nH2O {Ln = Gd (1); Ln = Dy (2)} and [Ln2Mn(IN)6Cl2(H2O)4]n·2nDMF {Ln = Gd (3); Ln = Dy (4), IN = isonicotinic cation}, were synthesized by using fractional crystallization and structurally characterized. Polymers 1 and 2 are isostructural and form a 2D double layer of [Ln4(µ3-OH)4] cubane and Mn(IN)4Cl2 units, whereas 3 and 4 are isomorphic and form a four-connected cds-type 3D framework assembled from paddle-wheel binuclear Ln2(COO)4 units and planar Mn(IN)4Cl2 units. Polymers 1–4 exhibited large magnetic entropy changes of 42.0, 16.7, 31.5, and 16.6 J kg–1 K–1, respectively (ΔH = 7 T). In addition, compounds 2 and 4 displayed field-induced slow magnetic relaxation behavior.Two series of Ln–MnII heterometallic coordination polymers, Ln8Mn3 {Ln = Gd (1); Ln = Dy (2)}, Ln2Mn {Ln = Gd (3); Ln = Dy (4)} were synthesized by using fractional crystallization and structurally characterized. Polymers 1–4 exhibit large magnetic entropy changes of 42.0, 16.7, 31.5, and 16.6 J kg–1 K–1, respectively (ΔH = 7 T). In addition, compounds 2 and 4 displayed a slow magnetic relaxation.
Datum: 27.07.2016

The Impact of Mesopores on the Mechanical Stability of HKUST-1: A Multiscale Investigation

Correlated missing node defects can lead to mesoporosity in MOFs. In order to investigate the effect of such cavities in the microporous crystalline material, spherical pores of increasing size were cut into HKUST-1, and the resulting inner surface was completely saturated. Our recently developed coarse-grained force field was used to relax these systems and to assess the mechanical stability by computing the bulk moduli. In a multiscale fashion, atomistic models were generated systematically from the coarse-grained relaxed structures in order to determine void fraction, surface area, and the relative mesoporous void volume. Despite the presence of mesopores with large radii of above 20 Å, the lattice parameters shrink only by a negligible amount. The bulk moduli are reduced, but overall a sufficient mechanical stability is found, consistently with experimental observations. Interestingly, for a fixed amount of defect degree, and thus mesoporous void volume, larger cavities lead to higher mechanical stability. For small mesopores in the size range below that of a HKUST-1 unit cell we observe unexpected trends due to the additional surface area generated by saturating the inner surface of the mesopore. With a large number of small mesopores, this can lead to an effective increase in the gravimetric surface area.The impact of mesopores due to defects in HKUST-1 on surface areas and mechanical stability was investigated by a multiscale simulation approach, combining coarse-grained and atomistic methods. The mechanical stability is related to size and concentration of the mesopores, and unexpected trends in volumetric and gravimetric surface area are pointed out.
Datum: 27.07.2016

Diastereoselective Synthesis of Pyranoquinolines on Zirconium-Containing UiO-66 Metal-Organic Frameworks

The Zr terephthalate MOFs UiO-66 and UiO-66-NH2 have been found to be highly diastereoselective catalysts for the synthesis of a pyrano[3,2-c]quinoline through an inverse electron-demand aza-Diels–Alder [4+2] cycloaddition of an aryl imine (formed in situ from aniline and benzaldehyde) and 3,4-dihydro-2H-pyran in one pot, affording the corresponding trans isomer in diastereomeric excesses of 90–95 %. The solids are stable under the reaction conditions and can be reused at least three times without significant loss of activity or diastereoselectivity.Zirconium-containing UiO-66-type compounds catalyze the Povarov reaction between an imine and dihydropyran at room temperature to give trans-pyrano[3,2-c]quinoline with diastereomeric excesses of 90–95 %. The solids are stable and reusable catalysts that show no significant loss of activity or diastereoselectivity.
Datum: 25.07.2016

One-Pot Hydrothermal Synthesis of Visible-Light-Responsive MoS2/g-CNO Heterostructures for Organic-Pollutant Degradation

MoS2/g-CNO (g-CNO = oxidized graphitic carbon nitride) heterostructures were synthesized by a one-step low-temperature hydrothermal route. The hydrolysis and oxidation reactions during the hydrothermal synthesis provide a fivefold increase in the surface area of the carbon nitride matrix. The heterostructure formation between MoS2 and the g-CNO matrix induced reduced recombination effects, and 1 wt.-% MoS2/g-CNO composites showed the highest photocatalytic activity towards the degradation of organic pollutants under visible-light irradiation. Moreover, owing to the presence of groups with negative inductive effects in g-CNO and g-CNO-based composites, the photocatalytic activities were higher than that of bare g-C3N4. Recyclability studies on the synthesized catalysts indicated no loss of efficiency after four cycles. Thus, these MoS2/g-CNO heterostructures are promising photocatalysts for the degradation of organic pollutants.Heterojunction catalysts with MoS2 integrated into oxidized graphitic carbon nitride material are synthesized by a one-step hydrothermal route. The materials are reusable photocatalysts for the degradation of organic pollutants.
Datum: 22.07.2016

Kinetics and Thermodynamics of Constitutional Dynamic Coordination Systems Based on FeII, CoII, NiII, CuII, and ZnII

The self-adaptation of constitutional dynamic systems based on selective coordination between 5,5′-dimethyl-2,2′-bipyridine and deuterium-labeled 4,4′-dimethyl-2,2′-bipyridine to FeII, CoII, NiII, CuII, or ZnII has been evaluated by ESI-MS in methanol. The equilibration rates of the systems proved dependent on the metal species, following the order ZnII > CuII > CoII > NiII > FeII, where ZnII resulted in rapid rearrangement of the original homoleptic complexes. The heteroleptic complexes were favored in the systems with CoII, CuII and ZnII, whereas the homoleptic complexes were more pronounced with FeII and NiII. The constitutional dynamics of adaptive coordination systems based on FeII, CoII, NiII, CuII, and ZnII has been evaluated by ESI-MS and NMR. The resulting dynamic equilibration processes could be easily followed over time, and the kinetic and thermodynamic properties assessed.
Datum: 22.07.2016

Observing the Effects of Shaping on Gas Adsorption in Metal-Organic Frameworks

A series of four micro- or mesoporous metal-organic frameworks [UiO-66(Zr), UiO-66(Zr)_NH2, MIL-100(Fe), MIL-127(Fe)] were synthesized in powder form and pelletized in the form of spheres by using a polyvinyl-based binder. The effect of pelletization on the adsorption of a series of gasses (N2, CO, CO2, CH4, C2H6, C3H8, C3H6, C4H10) at 303 K was evidenced in the adsorption isotherms and the enthalpies of adsorption measured by using microcalorimetric analysis. As expected, uptakes of gas per gram of material were lower for the spheres than for the powder. However, taking into account the bulk density, this tendency was inverted, suggesting that the spherical materials are of distinct interest for gas-based applications. Nevertheless, other effects including partial pore restriction and active site “protection” may equally be evidenced for some pelletized materials, suggesting that the polyvinyl binder may play a more complex role.A series of four metal-organic frameworks were synthesized as powders and spheres, and these were characterized by gas adsorption at 30 °C coupled with microcalorimetry. Whereas most variations were expected, interesting effects including partial pore restriction and active site “protection” were also evidenced for some shaped materials, suggesting that the binder may play a more complex role.
Datum: 22.07.2016

Luminescent Carbonyl Hydrido Ruthenium(II) Diimine Coordination Compounds: Structural, Photophysical, and Electrochemical Properties

A series of luminescent carbonyl hydrido ruthenium(II) complexes with various diimine ligands with diverse electronic properties, including Me2bpy (bpy = bipyridine), Me2phen (phen = phenanthroline), PhenCOOH, PhenCN, Me2Ph2phen, Ph2phen, and π-conjugating dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), dipyrido[3,2-a:2′,3′-c](6,7,8,9-tetrahydro)phenazine (dpqc), and dipyridophenazine (dppz) have been synthesized and characterized. Four of these complexes have been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been studied. The effects of the electronic features and π-conjugation of the diimine ligand on the electronic and photophysical properties of these complexes have also been discussed. Our study revealed that the luminescence performance of these complexes could be significantly enhanced by increasing the rigidity and π-conjugation of the diimine ligand. Luminescent carbonyl hydrido ruthenium(II) complexes with various diimine ligands have been synthesized. The effects of the electronic features and diimine ligand π-conjugation on the electronic and photophysical properties are discussed. The luminescence performance of these complexes could be significantly enhanced by increasing the rigidity and π-conjugation of the diimine ligand.
Datum: 22.07.2016

Unprecedented 3D and 2D Frameworks of Manganese Thioarsenates Based on Heterometallic Cubic Cluster [Mn6(µ6-S)(AsS3)4] and Covalent Linker N2H4

New Mn thioarsenates [Mn(dien)2][Mn6(µ6-S)(µ-N2H4)3(µ3-AsS3)4]·H2O (1) and [Mn(1,2-dap)3][Mn6(µ6-S)(N2H4)2(µ-N2H4)2(µ3-AsS3)4] (2) (dien = diethylenetriamine; 1,2-dap = 1,2-diaminopropane) were solvothermally synthesized with the synergistic assistance of coordinative polyamines and hydrazine. Compounds 1 and 2 contain a 3D {[Mn6(µ6-S)(µ-N2H4)3(µ3-AsS3)4]2–}⋡ network and a 2D {[Mn6(µ6-S)(N2H4)2(µ-N2H4)2(µ3-AsS3)4]2–}⋡ layer, respectively, which are constructed by cubic [Mn6(µ6-S)(µ3-AsS3)4] clusters and µ-N2H4 covalent linkers. In the [Mn6(µ6-S)(µ3-AsS3)4] cluster, four As3+ cations occupy the four opposite vertexes, and six Mn2+ cations are located at the face centers. An S2– anion at the heart of the cube coordinates to six Mn2+ cations at the face center in a µ6-S mode, generating an octahedral Mn6(µ6-S) core. The Mn6(µ6-S) core and µ6-S coordination mode are observed for the first time in the Mn/As/S system. In 1, the cubic [Mn6As4S13] clusters are connected into a 3D framework of {[Mn6(µ6-S)(µ-N2H4)3(µ3-AsS3)4]2–}⋡ anions through three µ-N2H4 bridging ligands. In 2, the [Mn6As4S13] cluster is joined by two µ-N2H4 bridging ligands and coordinated by two terminal N2H4 molecules, with formation of a 2D layer {[Mn6(µ6-S)(N2H4)2(µ-N2H4)2(µ3-AsS3)4]2–}⋡. The room-temperature band gaps of 1 and 2 are 2.21 and 2.34 eV, respectively.New Mn thioarsenates 1 and 2 based on the heterometallic cubic cluster [Mn6As4S13] were prepared with the assistance of the synergistic coordinating effect of hydrazine and ethylenepolyamine ligands. The 3D {[Mn6(µ6-S)(µ-N2H4)3(µ3-AsS3)4]2–}⋡ and 2D {[Mn6(µ6-S)(N2H4)2(µ-N2H4)2(µ3-AsS3)4]2–}⋡ clusters represent new types of structure and connectivity in compounds of the Mn/As/S family.
Datum: 22.07.2016

Unique Colours of 3d-Transition-Metal-Substituted Lyonsite Molybdates and Their Derivatives: The Role of Multiple Coordination Geometries and Metal-to-Metal Charge Transfer

We describe the synthesis, crystal structures, and optical absorption spectra/colours of 3d transition-metal-substituted lyonsite-type oxides Li3Al1–xMIIIx(MoO4)3 (0 < x ≤ 1.0; MIII = Cr, Fe) and Li3–xAl1–xMII2x(MoO4)3 (0 < x ≤ 1.0; MII = Co, Ni, Cu). The oxides were readily synthesized by the solid-state reaction of stoichiometric mixtures of the constituent binaries at around 700 °C in air. The crystal structures determined by Rietveld refinement of PXRD data revealed that in the smaller trivalent-metal-substituted lyonsite oxides, the MIII ions occupy the octahedral (8d, 4c) sites and the lithium ions occur exclusively at the trigonal-prismatic (4c) site in the orthorhombic (Pnma) structure. On the other hand, larger divalent-metal (CoII/CuII)-substituted derivatives show occupancy of the CoII/CuII ions at both the octahedral and trigonal-prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1–xMIIIx(MoO4)3 (MIII = Cr, Fe) and Li3–xAl1–xMII2x(MoO4)3 (MII = Co, Ni, Cu) and interpreted the results in terms of the average crystal field strengths experienced by MIII/MII ions in multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo 4d orbitals in the resulting colours of these oxides.Lyonsite molybdates containing 3d transition metals display bright and unique colours that arise from both ligand-field electronic transitions in distorted octahedral coordination geometries and 3d-metal-to-4d-Mo charge transfer. Accordingly, the work identifies the lyonsite framework structure as a novel platform for developing new inorganic pigments.
Datum: 22.07.2016

Five Disc-Shaped {MII7} (M = Mn, Fe, Co, Cu, Zn) and One Capsule-Like {CuII6NaI2} Clusters Assembled from an Identical Schiff Base Ligand

Six transition-metal clusters of compositions [Mn7L6](NO3)2·2CH3OH (1), [Fe7L6](NO3)2·2CH3OH (2), [Co7L6](NO3)2·2CH3OH (3), [Cu7L6](NO3)2 (4), [Zn7L6](NO3)2·2CH3OH (5), and [Cu6Na2L6](NO3)2·4CH3OH (6) {H2L = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol} have been synthesized under solvothermal conditions. The structures of 1–6 have been established based on single-crystal X-ray diffraction studies. Complexes 1–5 possess disk-shaped {MII7} cores, with the central MII ion and the six peripheral MII ions being linked by six µ3-O atoms. The six MII ions of the rim of the disk are bridged in a pairwise manner by six µ2-O atoms. Complex 2 is a very rare example of a disk-shaped {Fe7} cluster in which all of the Fe atoms exhibit +2 oxidation state. Furthermore, this is the first time that the five isostructural heptanuclear clusters were constructed by using an identical Schiff base ligand. The molecule of complex 6 contains a capsule-like {Cu6Na2} core. In this core, two sodium ions reside on the two vertices of the capsule and the 12 vertices of the {Cu6O6} hexagonal prism are occupied by alternately arrayed six CuII ions and six O atoms. Photoluminescence studies suggest strong emission for 5 in the solid state at room temperature. Variable-temperature dc magnetic susceptibility studies were carried out on polycrystalline samples of 1–4 and 6. The ac susceptibility studies were also performed with 3. Strong out-of-phase, χ′′, signals were observed for 3 at zero field, suggesting that 3 is a class of single molecule magnet (SMM).Five transition-metal {MII7} clusters and one capsule-like {Cu6Na2} compound have been synthesized by employing an identical Schiff base ligand. Complex {CoII7} exhibits single molecule magnetic behavior.
Datum: 19.07.2016

Formation of a Polythreaded, Metal–Organic Framework Utilizing an Interlocked Hexadentate, Carboxylate Linker

A unique hexacarboxylate linker was prepared on the basis of an interlocked [2]rotaxane motif. The linker contains four carboxylate groups attached to a rigid, H-shaped axle and two carboxylate units appended to a crown ether wheel. The resulting ZnII-based metal–organic framework material has a unique lattice, in which three independent 3-periodic frameworks (threefold interpenetration) are interconnected only by virtue of the threading of their individual components in the rotaxane linker.A hexacarboxylate ligand based on an interlocked [2]rotaxane motif is used to construct a ZnII metal–organic framework material. The structure has a unique lattice, in which three independent 3-periodic frameworks are interpenetrated only by virtue of the threading of their individual components (axle and wheel) in the rotaxane linker.
Datum: 18.07.2016

Substitution of Metallocenes with [2.2]Paracyclophane to Enable Confocal Microscopy Imaging in Living Cells

Bioimaging techniques that allow the visualization of ferrocene in living cells do not exist. This work addresses this challenging problem, and a new indirect approach for the bioimaging of ferrocenyl compounds in living and fixed cells is proposed. It is based on the structural similarity of metallocenyl (ferrocenyl and ruthenocenyl) groups to their metal-free [2.2]paracyclophanyl congeners. Three adequately designed compounds were obtained. They share a 5-(1-ethynylpyrenyl)uracil group as a common structural motif and differ in their three-dimensional aromatic substituents, namely, [2.2]paracyclophanyl, ferrocenyl and ruthenocenyl. The first substituent allows pyrenyl luminescence to occur, whereas the latter two act as quenchers. The accumulation of the luminescent derivative in the membranes, cytoplasm and mitochondria of living and fixed cells was confirmed by confocal microscopy. Microscopy studies were further correlated with high-resolution continuum-source atomic absorption spectroscopy (HR-CS AAS) measurements of the ruthenocenyl compound that confirmed the uptake of ruthenium into the cells. Thus, taking into account the overall similarity of the compounds under study, it can be hypothesized that the metallocenyl derivatives are localized in the membranes, cytoplasm and mitochondria of the assayed cells. This is the basis for the more general concept of the utilization of luminescent [2.2]paracyclophanes as probes in indirect bioimaging studies of metallocene derivatives.The biodistribution of metallocenyl uracil–pyrenes is investigated through an indirect approach that exploits the structural similarities of metallocenyl and [2.2]paracyclophanyl groups. Confocal microscopy of a [2.2]paracyclophane uracil–pyrene shows its accumulation in the membranes, cytoplasm, and mitochondria. A similar biodistribution pattern is postulated for the metallocenyl congeners.
Datum: 13.07.2016

Adding to the Arsenal of Zirconium-Based Metal–Organic Frameworks: the Topology as a Platform for Solvent-Assisted Metal Incorporation

Gaining control over the assembly of mesoporous Zr-based metal–organic frameworks (MOFs) with modifiable metal nodes remains a challenge. The the topology is intriguing, particularly if considering postsynthetic modification, as it presents large sodalite-like cages surrounded by 12 interconnected 1D channels that allow for efficient diffusion of guest molecules throughout the structure. Herein, we demonstrate the first Zr MOF with the topology, NU-1200, which was synthesized by controlling the geometry of the organic building unit. In addition, by using NU-1200 as a platform, we perform solvent-assisted metal incorporation to form single-site metalated nodes, a process that is characterized by single-crystal X-ray diffraction.NU-1200 is a Zr-based metal–organic framework (MOF) with the topology. Consisting of unsaturated Zr6 oxide nodes and triangular linkers with large interconnected channels, this MOF is an ideal candidate for postsynthesis metalation.
Datum: 08.07.2016

Synthesis of Phosphanylferrocenecarboxamides Bearing Guanidinium Substituents and Their Application in the Palladium-Catalyzed Cross-Coupling of Boronic Acids with Acyl Chlorides

Phosphanylferrocene donors bearing polar guanidinium substituents, namely acylguanidinium chloride, [Ph2PfcCONHC(NH2)NH2]Cl (1), and amidoguanidinium chloride, [Ph2PfcCONHCH2CH2NHC(NH2)NH2]Cl (2; fc = ferrocene-1,1′-diyl), have been prepared and characterized. As functional phosphane donors, they were employed in the synthesis of PdII complexes bearing 2-[(dimethylamino)methyl-κN]phenyl-κC1 (LNC) and η3-allyl supporting ligands, [(LNC)PdCl(L-κP)] and [(η3-C3H5)PdCl(L-κP)] (L = 1 and 2), respectively. These defined complexes as well as their surrogates generated in situ from the respective palladium(II) precursor and the phosphanylferrocene ligand were evaluated as catalysts for the coupling of boronic acids with acyl chlorides to give ketones in an aqueous biphasic system. The coupling reaction proceeded best with a simple catalyst formed from Pd(OAc)2 and ligand 2, which (at 0.2 mol-% Pd loading) produced substituted benzophenones from benzoyl chlorides and benzeneboronic acids in very good yields. These yields could then be further improved by a proper choice of the reaction partners. Analogous reactions involving aliphatic substrates generally afforded lower yields.Phosphanylferrocene ligands 1 and 2 bearing guanidinium pendants have been prepared and utilized as donors in PdII complexes and in the Pd-catalyzed cross-coupling of arylboronic acids with benzoyl chlorides to give benzophenones. Consistently better results were achieved with ligand 2 possessing an extended alkylguanidinium moiety appended to the phosphanylferrocene unit through an amide moiety.
Datum: 06.07.2016

Impact of the Metal Centre and Functionalization on the Mechanical Behaviour of MIL-53 Metal–Organic Frameworks

An extended series of MIL-53(M)_X metal–organic frameworks (MIL = Materials of Institute Lavoisier; M = Al, Cr, Fe, Sc; X = Cl, CH3, NO2) have been systematically investiaged to explore the impact of the nature of both the metal centre and the functions grafted on to the organic linker on the mechanical behaviour of this family of highly flexible hybrid porous frameworks under the application of an external pressure of up to 3 GPa. The high-pressure X-ray diffraction measurements allowed the characterization of the pressure-induced phase transitions of the hydrated structures, the associated volume changes/pressure transitions, and their mechanical resilience through the determination of their bulk moduli.The pressure-induced phase transitions of a series of hydrated MIL-53 metal–organic frameworks and their compressibility have been investigated as a function of the nature of both the metal centre and the functions grafted on to the organic linker.
Datum: 04.07.2016

A Facile Synthesis of Co3O4 Hollow Microtubes by Decomposition of a Cobalt Metal–Organic Framework

In this work, we have successfully synthesized hollow microtubular crystals of the metal–organic framework (MOF) [Co2(NH2-bdc)2(dabco)]·[G] {G = H2O, N,N-dimethylformamide (DMF); NH2-bdc =2-amino-1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane} by a very simple coordination-modulation method that avoids the use of an external modulator. Additionally, we have obtained the corresponding hollow microtubular crystals of Co3O4 through the solid-state thermolysis of the Co-MOF material at 400 °C. The as-prepared Co3O4 crystals exhibit the typical magnetic behavior for a nanostructured material with good crystallinity. Thus, this coordination-modulation method provides a simple route for the preparation of nanostructured porous frameworks and derived oxides and opens a way to prepare new materials with advanced properties. We obtained the metal–organic framework [Co2(NH2-bdc)2(dabco)]·[G] {G = H2O, N,N-dimethylformamide; NH2-bdc = 2-amino-1,4-benzenedicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane} as hollow microtubes and synthesized microtubular crystals of Co3O4 by calcination at 400 °C. The coordination-modulation method provides a simple route to nanostructured porous frameworks and derived oxides.
Datum: 04.07.2016

Synthesis and Structural Characterization of Mono- and Bimetallic Rhodium(I), Iridium(I) and Gold(I) Methanide and Methandiide Complexes from 2-Quinolyl-Linked (Thiophosphoranyl)methane

The synthesis and structural characterization of RhI, IrI and AuI metal complexes derived from 2-quinolyl-linked (thiophosphoranyl)methane CH2(iPr2P=S)(C9H6N-2) (A) are reported. Metathesis reactions of 2-quinolyl-thiophosphinoyl potassium complex [K{CH(iPr2P-S)(C9H6N-2)}]n (1) with 1 equiv. of [MCl(COD)]2 (M = Rh, Ir; COD = cycloocta-1,5-diene) afforded monomeric 2-quinolyl-thiophosphinoyl-rhodium(I) and iridium(I) complex [M(COD){CH(iPr2P=S)(C9H6N-2)}] {M = Rh (2), Ir (3)}, respectively. Upon treatment of 1 with 2 equiv. of [MCl(COD)]2 (M = Ir, Rh), bimetallic complexes [M(COD){CH(iPr2P=S)(C9H6N-2)(M(COD)Cl)}] {M = Rh (4), Ir (5)} were obtained. The reaction of 1 with [AuCl(PPh3)] afforded a geminal dinuclear gold(I) methandiide complex [{Au(PPh3)}2{C(iPr2P-S)(C9H6N-2)}] (6), featuring an aurophilic interaction. Meanwhile, the metathesis reaction of 1 with 1 equiv. of gold(I) complex [AuCl(IPrNHC)] {IPrNHC = C[N(2,6-iPr2C6H3)CH]2} afforded a monomeric two-coordinate monoaurated product, 2-quinolyl-thiophosphinoyl-gold(I) N-heterocyclic carbene complex [Au(IPrNHC){CH(iPr2P-S)(C9H6N-2)}] (7). The structures of 3–7 have been determined by X-ray crystallography and the UV/Vis absorption properties of 2–6 have also been studied. A series of mono- and bimetallic rhodium(I), iridium(I) and gold(I) metal complexes have been synthesized and structurally characterized by X-ray crystallography.
Datum: 04.07.2016

Controlling the Growth of Metal-Organic Frameworks Using Different Gravitational-Forces

Control over Metal-organic framework (MOF) size and morphology is interesting for both fundamental and applied science. Gravitational force (g) is generally acknowledged as an interesting parameter for controlling crystal size; however, a dedicated study on the effect of g on MOF synthesis is missing. Here, we investigate the effect of varied g (< 1, 1, 20, 50, and 100) during the crystallization of different MOFs [ZIF-8, Tb2(BDC)3 and HKUST-1] in solution. The obtained MOFs were investigated using dynamic light scattering (DLS), X-ray scattering (SAXS and WAXS), and scanning electron and optical microscopy (SEM and OM, respectively). When compared with standard g (g = 1), high g (g = 20) gave rise to the formation of smaller MOF crystals, while low g (g < 1) led to larger crystals likely due to facet-oriented crystal fusion. This demonstrates that gravity and g-force can be used to rationally control the size of different MOFs by increasing or decreasing convection (mass transfer) and sedimentation.Metal-organic frameworks (MOFs) are grown under different gravitational forces. We demonstrate that larger MOFs grow at lower g-force (g < 1), while smaller MOFs grow at higher g-force (g = 20). This data matches well with historical studies on crystal growth in microgravity, suggesting that the MOFs explored herein are governed by similar growth mechanisms to a wide variety of other crystals.
Datum: 04.07.2016

Conducting Behavior and Valence Ordering of a One-Dimensional MMX-Type Coordination Polymer under High Pressure

One-dimensional (1D) halogen-bridged mixed-valent binuclear metal compounds, the so-called MMX chains, are well known as highly conductive coordination polymers because of the high electronic flexibility within their metal-dimer unit. Herein, we report on the conducting behavior and electronic state of a highly conductive MMX-chain compound, Pt2(dta)4I (dta: CH3CS2–) under high pressure. Electrical resistivity measurements showed that this compound exhibits semiconducting behavior in a broad pressure region, despite metallic conduction under ambient pressure. Raman spectra provided clear information about the semiconducting state of this compound under pressure, which was also supported by X-ray diffraction (XRD) studies. Moreover, we successfully clarified the pressure–temperature phase diagram of this material. By comparing with an analogous material, we found that the difference in the alkyl chain length of the terminal ligand plays an important role for the conducting behavior and the electronic phase under pressure.We report on the conducting behavior and electronic state of a highly conductive MMX-type coordination polymer, Pt2(dta)4I (dta: CH3CS2–), under high pressure. This compound shows semiconducting behavior up to 8 GPa. Raman and X-ray diffraction (XRD) studies clearly revealed the electronic states under pressure. In addition, the pressure–temperature phase diagram of this compound was clarified.
Datum: 04.07.2016

A Promising Catalytic and Theranostic Agent Obtained through the In-Situ Synthesis of Au Nanoparticles with a Reduced Polyoxometalate Incorporated within Mesoporous MIL-101

A well-controlled three-step green synthetic method allows the synthesis of composite materials based on the highly stable chromium(III) terephthalate MIL-101(Cr) with gold nanoparticles (NPs) and polyoxometalates (POMs) inside its mesopores. First, the POM was included within the MIL-101(Cr) cavities through the direct synthesis of MIL-101(Cr) in the presence of the preformed H3PMo12O40 POM. Then, the incorporated POM was reduced in situ with H2. Finally, an in-situ soft reduction of HAuCl4 by the reduced POM led to the formation of Au NPs and oxidized POM within the MIL-101(Cr) structure [(Au)H2redPOM@101]. A final Au/POM atomic ratio of 1.8 was reached. The chemical and structural stabilities of both MIL-101(Cr) and the POM were preserved during the whole process. In addition to the potential catalytic properties of these highly porous composite systems, we have demonstrated their promising performance as optical contrast agents. The (Au)H2redPOM@101 composites exhibited excellent biostability and were rapidly internalized in macrophage cells, as observed through fluorescence confocal microscopy.Promising catalysts and optical contrast agents based on (Au)POM@MOF (POM = polyoxometalate, MOF = metal–organic framework) composites are synthesized in situ through the incorporation of a POM into the mesopores of MIL-101, followed by reduction to form Au nanoparticles. These composites are internalized rapidly by cells, and no Au/POM leaching or MOF biodegradation occurs.
Datum: 27.06.2016

Difluorotriorganylphosphoranes for the Synthesis of Fluorophosphonium and Bismuthonium Salts

Fluoride ion affinities (FIA), provided by DFT calculations, are exceedingly useful for the design of new Lewis acids with defined reactivities. Herein, we report the synthesis, characterization and reactivity of new difluoro(perfluoroorganyl)phosphoranes, which readily abstract fluoride ions from difluoro(triorganyl)phosphoranes. Highly reactive fluorobismuthonium cations and the [Ph3Bi(NCCH3)2]2+ cation are accessible through the treatment of difluoro(triorganyl)bismuth(V) compounds with the Lewis acidic phosphoranes discussed here. Highly reactive fluorophosphonium cations, [R3PF]+, previously unknown fluorobismuthonium cations, [R3BiF]+, and triarylbismuth dications, [R3Bi]2+, are conveniently available by the reactions of difluoro(triaryl)pnictogens with new difluoro(perfluoroorganyl)phosphoranes.
Datum: 27.06.2016

Quantum Sieving for Separation of Hydrogen Isotopes Using MOFs

Hydrogen isotope mixtures can be separated either by confinement in small pores [i.e., “kinetic quantum sieving” (KQS)] or by strong adsorption sites [i.e., “chemical affinity quantum sieving” (CAQS)]. MOFs are excellent candidates for study of these quantum effects, due to their well-defined, tunable pore structures and the potential to introduce strong adsorption sites directly into the framework structure. In this microreview we summarize the recent status of hydrogen isotope separation using MOFs and future strategies relating to it. Furthermore, a state-of-the-art technique for the direct measurement of selectivity with regard to isotope mixtures is introduced. Experimental results relating to separation factors with different pore apertures in the case of KQS and the role of open metal sites in that of CAQS as a function of temperature and gas pressure are given. Furthermore, technologically relevant parameters such as feasible operating pressure and temperature are discussed with respect to possible applications in a temperature swing process.Two mechanisms for hydrogen isotope separation using MOFs are introduced: “kinetic quantum sieving (KQS) with confinement in small pores” and “chemical affinity quantum sieving (CAQS) by strong adsorption sites”. In addition, the recent status and future strategies for hydrogen isotope separation with the aid of MOFs is discussed.
Datum: 22.06.2016

Vapochromic Luminescence of a Zirconium-Based Metal–Organic Framework for Sensing Applications

For the integration of responsive molecular units into chemically stable metal–organic frameworks (MOFs), the luminescent ligand 9-fluoreneone-2,7-dicarboxylic acid (H2FDC) was utilised in a reaction with Zr4+. The resulting framework has fcu topology and is permanently porous with a BET surface area of 1428 m2 g–1. The MOF shows guest-responsive fluorescent properties and is therefore suitable for application in sensing of solvent vapours. Saturated vapours of non-polar aromatic and non-aromatic compounds can be distinguished on the basis of their shifts in the fluorescence emission peak. Polar solvents are also distinguishable, whereas aprotic solvents induce a hypsochromic and protic solvents a bathochromic shift. Furthermore, different alcohols can be distinguished from each other. In the case of water, the significant dependence of the emission wavelength on the concentration demonstrates the potential of the MOF as a humidity sensor.Integration of fluorenone cores into a zirconium metal–organic framework (MOF) results in sensitive vapochromic luminescence. The MOF shows significant changes in the emission spectrum in response to solvent-vapour exposure, which makes this material a potential candidate for luminescence-based sensing applications.
Datum: 22.06.2016

Flexible Metal–Organic Frameworks with Discriminatory Gate-Opening Effect for the Separation of Acetylene from Ethylene/Acetylene Mixtures

Adsorptive separation of acetylene from ethylene/acetylene mixtures is a technologically very important and highly challenging task. In this work, we describe two flexible metal–organic frameworks (MOFs), ELM-11 and ELM-13, that display adsorbate discriminatory gate effects. The two MOFs exhibit gate-opening-type adsorption properties for C2H2 but not for C2H4, leading to a highly selective adsorption of acetylene over ethylene at 273–298 K. The potential of the flexible MOFs for the separation is established by combining measurements of adsorption isotherms, ideal adsorbed solution theory (IAST) calculations of the adsorption equilibrium of the mixture, and transient breakthrough experiments. The results suggest the potential of both flexible MOFs for the industrial removal of acetylene from ethylene/acetylene mixtures through the energy-efficient adsorption separation process.Two flexible metal–organic frameworks (MOFs) exhibit gate-opening-type adsorption properties for acetylene but not for ethylene, leading to a highly selective adsorption of acetylene over ethylene at 273–298 K. The results suggest the potential of both flexible MOFs for industrial acetylene/ethylene separation through the energy-efficient adsorption separation process.
Datum: 22.06.2016

10000-Fold Enhancement in Proton Conduction by Doping of Cesium Ions in a Proton-Conducting Zwitterionic Metal–Organic Framework

Developing metal–organic framework (MOF)-based proton-conducting electrolytes for fuel-cell applications is an important target that has drawn a lot of attention. A key approach involves the selective replacement of the guest species within the pores to enhance performance. The modular and crystalline nature of the MOF permits controlled introduction of such species and characterization of their compositions with high precision, a task which is very difficult to achieve in amorphous polymers. Herein, we partially replaced the protons of a zwitterionic pyridinol in Mg(terephthalate)(pyridinol) MOF 1 with Cs+ ions, which brought about a 10000-fold increase in the proton conductivity (10–6 to 10–2 S cm–1). Interestingly, Li+ ions could not be loaded, whereas Cs+ ions with smaller hydrated ionic radii could be loaded, and the loading was controlled as a function of time. The Cs+ loading nearly halved the activation energy (from 0.35 for 1 to 0.19 eV for 1_Cs). The highest conductivities were realized for an optimal loading of Cs+ ions, which was found to be about 10 % in this case. Partial replacement of protons from a zwitterionic pyridinol of a Mg(terephthalate) metal–organic framework by about 10 % Cs+ ions provides a 10000-fold enhancement in proton conductivity. The concentration of Cs+ needs to be optimal to realize this maximum enhancement.
Datum: 20.06.2016

A Facile “Green” Route for Scalable Batch Production and Continuous Synthesis of Zirconium MOFs

Considering the requirements for the commercial production of metal–organic frameworks (MOFs), we investigated the aqueous synthesis of zirconium MOFs. A highly versatile route was identified employing ZrOCl2·8H2O, H2O, acetic acid and the respective linker molecule as starting materials. These synthesis conditions are suitable to obtain zirconium MOFs with different topologies like UiO-66-(OH)2, zirconium fumarate, zirconium mesaconate, DUT-67 or MOF-808 with synthesis times of 1 to 5 h under microwave irradiation. The scalability of the synthesis of zirconium fumarate was demonstrated at multigram scale under reflux conditions using conventional dielectric heating. To ease the recovery of this MOF which bypasses filter paper as a pure product, we identified sodium polyacrylate as a suitable additive to induce aggregation of the particles. Moreover, a custom-made prototype flow reactor was developed which allows for the continuous synthesis of zirconium fumarate and UiO-66-NH2 starting from a slurry of the starting materials. The commonly employed toxic organic solvents needed for activation/purification of the MOFs could be successfully replaced by a basic aqueous solution. A “green” preparative route for the synthesis of zirconium MOFs with diverse topologies was developed. This allows the synthesis of multigram amounts in batch reactions or under continuous flow conditions.
Datum: 16.06.2016

Quantitative Structure–Property Relationship Models for Recognizing Metal Organic Frameworks (MOFs) with High CO2 Working Capacity and CO2/CH4 Selectivity for Methane Purification

Metal-organic frameworks (MOFs) can theoretically yield a nearly infinite number of nanoporous materials, which represents a combinatorial design challenge that demands computational tools rather than experimental trial-and-error. Here we report Quantitative Structure–Property Relationship (QSPR) models to identify high-performing MOFs for methane purification solely using geometrical features. The CO2 working capacity and CO2/CH4 selectivity of ca. 320,000 hypothetical MOF structures was computed at conditions relevant to natural gas purification using grand canonical Monte-Carlo (GCMC) simulations. Using 32,500 MOF structures we calibrated binary decision tree (DT) and support vector machine (SVM) models that can accurately identify high-performing MOFs based on their pore size, void fraction and surface area. DT models yielded guidelines of pore size, void fraction and surface area for designing high-performing materials. The SVM machine learning classifiers could be used to quickly pre-screen MOFs, such that compute intensive GCMC simulations are not performed on all structures. The SVM classifiers were tested on ca. 290,000 MOFs that were not part of the training set and could correctly identify up to 90 % of high-performing MOFs while only flagging a fraction of the MOFs for more rigorous screening. QSPR models constitute efficient computational tools for the virtual screening of large structural libraries and provide rational design rules for the discovery of sorbents for methane purification.Robust machine learning QSPR models have been developed to accurately recognize high-performing metal organic framework materials for both the working capacity and selectivity in CO2/CH4 gas separations under methane purification conditions. The models were trained on 32,500 MOFs and validated on a test set of ca. 290,000 hypothetical MOFs.
Datum: 15.06.2016

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