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



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


Front Cover: Sulfur versus Dioxygen: Dinuclear (Trisulfido)copper Complexes (Eur. J. Inorg. Chem. 21/2016)

The cover picture shows elemental sulfur in the crater of the volcano on the Vulcano island, Italy (photograph courtesy of Christopher Schmidt, Marburg). Sulfur is one of the few elements that can be found in its elemental form in nature. It is quite likely that sulfur was a key element for the evolution of life. A macrocylic copper(I) complex with the ligand tet b (= rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) can easily react with elemental sulfur to form a dinuclear product complex with a bridging trisulfido ligand. Details are discussed in the article by S. Schindler et al. on p. 3384 ff. For more on the story behind the cover research, see the Cover Profile.
Datum: 22.07.2016


Sulfur versus Dioxygen: Dinuclear (Trisulfido)copper Complexes

Invited for the cover of this issue are the groups of Siegfried Schindler and Doreen Mollenhauer from the Justus-Liebig University Gießen, Germany. The cover image shows the reaction of a copper(I) complex with elemental sulfur. It was quite surprising that sulfido ligands can be easily substituted with peroxido ligands in the reaction of copper sulfido complexes with dioxygen…Read more about the story behind the cover in the Cover Profile and about the research itself on p. 3384 ff.
Datum: 22.07.2016


Spotlights on our sister journals: Eur. J. Inorg. Chem. 21/2016


Datum: 22.07.2016


A Quantitative Description of the σ-Donor and π-Acceptor Properties of Substituted Phenanthrolines

The bond between molybdenum and substituted 1,10-phenanthroline ligands in a series of [Mo(CO)4(phen*)] complexes has been studied by combining experimental data (νCO) with DFT calculations. First, natural orbitals for chemical valence (NOCV) were calculated: The resulting charge-transfer magnitudes (Δqi) associated with the deformation density channels (Δϱi) were related to σ-donation and π-back-donation. Then, energy decomposition analysis was performed by applying the extended transition state (ETS) scheme. The outcomes of the ETS-NOCV approach has allowed us to quantify the energetic contribution of both ligand-to-metal (Eσ) and metal-to-ligand (Eπ) interactions. A new parameter (Tphen) has been introduced comprising both Eσ and Eπ and thus providing a descriptor for the overall electronic contribution given by phenanthrolines to the metal–ligand bond. This was corroborated by the linear correlation found between Tphen and the νCO vibration modes of [Mo(CO)4(phen*)] complexes, at least for those containing a 2,9-unsubstituted phenanthroline. The case of [Mo(CO)4(phen*)] derivatives with a 2,9-substituted phen* is also discussed.Like players of opponent teams in rugby, σ and π contributions are involved in a sort of “electronic scrum” that determines the nature of metal–ligand bonds. An ETS-NOCV study allowed us to quantify these contributions, associated with Eσ and Eπ, in [Mo(CO)4(phen*)] compounds. A new electronic parameter (Tphen) comprising both Eσ and Eπ has been introduced and correlated with experimental data.
Datum: 20.07.2016


One-Pot Intermolecular C–S Self-Coupling of Dimethyl Sulfoxide Promoted by Molybdenum Pentachloride

The reactions between MoCl5 and 1–2 equiv. of a selection of sulfoxides at room temperature in dichloromethane as solvent were studied. The 1:1 molar reaction between MoCl5 and dimethyl sulfoxide (DMSO) afforded the C–S coupling product [Me2SCH2SMe][MoOCl4] (1), which was isolated in 46 % yield and characterized by analytical and spectroscopic methods and by X-ray diffraction. MoOCl3, SMe2 and HCl were identified as side products. The reactions between MoCl5 and tetrahydrothiophene 1-oxide, nBu2SO, MePhSO or (PhCH2)2SO yielded the corresponding sulfides and, in the cases of (PhCH2)2SO and MePhSO, also C–S activation compounds. According to DFT calculations, the unusual formation of 1 is the consequence of thermodynamically feasible Cl/O interchange between MoCl5 and DMSO, this being a prerequisite for successive C–H bond activation.The reactions between MoCl5 and limited amounts of a selection of sulfoxides are reported. The unusual, one-pot conversion of DMSO into a mercaptomethylsulfonium salt has been studied by means of X-ray crystallography, DFT calculations and spectroscopic and analytical techniques.
Datum: 20.07.2016


Highly Robust Terbium Coordination Polymer as a Multi-responsive Sensor Showing Sensitive Luminescent Detection for Pollutional Anions

An ultrastable Tb-coordination polymer TbL2 (HL = 4-(pyrimidin-5-yl) benzoic acid) was successfully synthesized, which exhibits high thermostability and chemical stability. TbL2 as a visual multi-responsive luminescent probe can highly selectively detect F- from same main group anions as well as various pollutional phosphorus anions.
Datum: 19.07.2016


Dual Role of Acetate in Copper(II) Acetate Catalyzed Dehydrogenation of Chelating Aromatic Secondary Amines: A Kinetic Case Study of Copper-Catalyzed Oxidation Reactions

Copper(II) acetate is a frequent empirical choice of the copper source in copper(II)-mediated redox reactions. The effect of the acetate counterion appears crucial but has not been adequately investigated. Herein, we report that copper(II) acetate catalyzes the aerobic dehydrogenation of chelating aromatic secondary amines. The chemoselectivity of acetate and chelating amines in this reaction provides a unique opportunity for a mechanistic study. The progression of this homogeneous reaction is monitored by using electron paramagnetic resonance spectroscopy, UV/Vis absorption spectroscopy, and manometry. The kinetic dependence on the amine substrate, copper(II), and acetate counterion, together with the results of kinetic isotope and substituent effect experiments, suggests that acetate acts both as a bridging ligand of a dinuclear catalytic center for mediating two-electron transfer steps and as a base in the turnover-limiting C–H bond-cleavage step. Upon including 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a surrogate base, DBU and acetate act in a complementary manner to enable a rapid, catalytic dehydrogenation reaction of a chelating secondary amine substrate. Finally, the contrasting reactivities between copper(II) acetate (promoting two-electron transfer) and copper(II) perchlorate (promoting single-electron transfer) underscores how a counterion could completely alter the mechanistic pathway of a copper-mediated oxidation reaction.The acetate ion accelerates the dehydrogenation of chelating secondary aromatic amines by acting as a base and a bridging ligand for the dinuclear copper catalytic center. The two-electron oxidation turnover-limiting step is therefore mediated by the redox conversion of a dicopper center from the +2 to +1 oxidation state.
Datum: 19.07.2016


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


Experimental and Theoretical Studies on the Crystal Structure of Ternary Copper Arsenides A2Cu3As3 (A = Sr, Eu)

Two new ternary copper-containing arsenides, Sr2Cu3As3 and Eu2Cu3As3, were synthesized through Pb-flux reactions. In combination with theoretical calculations, the crystal structures of these compounds were determined through single-crystal X-ray diffraction. Both compounds crystallize in the orthorhombic space group Cmcm (no.63) with the cell parameters a = 4.2465(6)/4.1866(5) Å, b = 17.604(3)/17.486(2) Å, and c = 4.2552(6)/4.2096(5) Å for the Sr- and Eu-containing compounds, respectively. Temperature-dependent magnetic susceptibility measurements suggest that both ferromagnetic and antiferromagnetic coupling exists in the structure of Eu2Cu3As3 for the Eu 4f states. According to DFT calculations, these compounds are metallic, and the Cu 3d orbitals make significant contributions to the states around the Fermi level.Two ternary copper-containing arsenides, Sr2Cu3As3 and Eu2Cu3As3, are synthesized, and their crystal structures are characterized by single-crystal XRD. The coexistence of ferromagnetic and antiferromagnetic order is observed. Theoretical calculations indicate that the Cu 3d orbitals make significant contributions around the Fermi level and also play an important role in the structure formation.
Datum: 19.07.2016


Multi-Readout Logic Gate for the Selective Detection of Metal Ions at the Parts Per Billion Level

Optical sensors utilizing visual responses for the identification of metal ions require reliable molecular systems able to operate selectively in multicomponent solutions. Herein, we report a water-soluble terpyridyl-based ligand that demonstrates effective quantification of parts per billion to parts per million levels of Fe2+, Fe3+, Zn2+, and Ru3+. Whereas the Fe3+ and Ru3+ ions were found to bind to the ligand to form a monometallic complex, a 2:1 ligand/metal binding stoichiometry was found for the Zn2+ and Fe2+ complexes. The corresponding metal-binding events were directly translated into distinct colorimetric and spectroscopic logic outputs. Applying molecular logic (Boolean logic operations) to describe these binding events, selective discrimination between the ions was demonstrated.A sensing platform for the rapid and sensitive detection of Fe2+, Fe3+, Ru3+, and Zn2+ in aqueous solutions is proposed. Boolean logic is applied to describe the interactions between the ligand (as a logic gate) and four target cations (logical inputs). The crystallographically determined structure of the [Fe(terpy-PO3Et2)2](ClO4)2 (terpy = 2,2′:6′,2′′-terpyridine) complex is presented.
Datum: 18.07.2016


Bonding Analysis in Homo- and Hetero-Trihalide Species: A Charge Displacement Study

The bonding in homo- (X3–) and hetero-trihalides (XYX–), with X = F, Cl, Br, and I; Y = I, has been analyzed through the charge displacement (CD) method, coupled with energy decomposition analysis (EDA). We focus our attention on how the different bond components vary with the distance between the terminal and the central halogen atoms. The results clearly show that all the homo-halide systems X3– feature the same trend of the charge transfer (CT) versus the asymmetry of the three-body system, defined as the ratio between the two bond lengths dX1–X2 and dX2–X3, whereas in the case of the hetero-trihalides BrIBr– and ClICl–, the CT values are similar, but systematically lower with respect to the homo-trihalide case. Comparison with solid-state geometries also allows us to estimate the influence of the crystal lattice (the packing and the interactions with the surrounding fragments) on the geometry. Following the results reported here, the CD method is confirmed to be a useful alternative computational tool to analyze the nature and the origin of weak intermolecular interactions such as halogen and hydrogen bonding. The bonding in homo- and hetero-trihalide species has been investigated by integrating charge displacement results in the function of the X1···X2 distance with energy decomposition analysis.
Datum: 18.07.2016


Formation of C@Fe3O4@C Hollow Sandwiched Structures with Enhanced Lithium-Storage Properties

Transition-metal oxides are considered promising anode materials for lithium-ion batteries (LIBs). However, their application is limited because of huge volume changes and poor conductivity during the discharge/charge process. To this end, integration of different active components into an assemblage poses a potential solution. To gain better structural and synthetic control, the integration should be executed in a stepwise manner. In this paper, a versatile strategy to obtain C@Fe3O4@C hollow sandwiched composite structures was explored. Starting from Fe2O3 nanotubes, a RF (resorcinol–formaldehyde resins) layer was sequentially applied outside to form RF@Fe2O3@RF structures, which were calcined to realize carbonization and finalize the C@Fe3O4@C sandwiched structures. To the best of our knowledge, this is the first study on the preparation of a novel Fe3O4/carbon-based nanocomposite. Upon using as an anode material for LIBs, the C@Fe3O4@C hollow sandwiched structures displayed high reversible capacity and good rate performance. The discharge capacity was maintained at 593 mA h g–1 after 350 cycles at a current density of 1000 mA g–1, which is better than that of Fe2O3 nanotubes (discharge capacity of 140 mA h g–1 after 80 cycles at 500 mA g–1). The improved electrochemical performance was attributed to the unique hollow sandwiched composite structure and good electrical conductivity.C@Fe3O4@C hollow sandwiched composite structures are obtained by a hydrothermal process and are coated with a resorcinol–formaldehyde (RF) resin layer by the sol–gel method, followed by subsequent thermal treatment. The excellent electrochemical activities are due to the unique hollow sandwiched composite structure and good electrical conductivity.
Datum: 18.07.2016


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


Synthesis, Characterization, and Catalytic Application of Mononuclear and Dendritic Cationic CuI Iminopyridine-Ligated Complexes in Aryl Iodide Hydroxylation

A series of mononuclear (C1–C4) and dendritic G1 (DC1–DC4) and G2 (DC5–DC8) cationic CuI iminopyridine complexes of the general formula [Cu{(R-C5H3N)CH=N(nPr)-κ2-N,N}2][BF4] (C1: R = 6-Me; C2: R = H; C3: R = 6-Br; C4: R = C4H3) and [DAB-Gx-PPI-(Cu{(R-C5H3N)-κ2-N,N}y)z][BF4]n [DAB: 1,4-diaminobutane; PPI: poly(propyleneimine); for G1: x = 1, y = 4, z = 2, n = 2; for G2: x = 2, y = 8, z = 4, n = 4; DC1/DC5: R = 6-Me; DC2/DC6: R = H; DC3/DC7: R = 6-Br; DC4/DC8: R = C4H3] have been prepared and characterized by a range of spectroscopic and analytical techniques. The mononuclear and dendritic complexes were found to be active catalysts for the hydroxylation of 4-iodotoluene to p-cresol in DMSO/H2O mixtures. A positive dendritic effect on catalytic activity was observed. Furthermore, our catalyst system was found to be active for the hydroxylation of 4-iodotoluene in neat water. The active catalyst could be recycled twice before catalyst deactivation was observed. HRTEM analysis revealed that catalyst deactivation arose as a result of metal agglomeration. A series of poisoning experiments provided evidence for the mediation of hydroxylation by a homogeneous active species for both classes of pre-catalysts, and a radical-trapping experiment in combination with our experimental observations provided evidence that the reaction proceeds through a similar mechanism to that reported for Cu-catalyzed halide exchange.Mononuclear and dendritic cationic complexes bearing iminopyridine-based ligands have been evaluated as catalysts for the hydroxylation of 4-iodotoluene. A dendritic analogue displayed high catalytic activity and recyclability in neat water without requiring a phase-transfer agent. Catalyst deactivation in water was found to proceed by metal agglomeration.
Datum: 18.07.2016


Synthesis and Spectroscopic Studies of the Photochromism of Bifunctional Derivatives of Cymantrene in Solution and without Solvent

Four monosubstituted cymantrene derivatives (5–8) containing two functional groups (allyl and amide) in a dendritic substituent were synthesized. The irradiation of these compounds with an Hg lamp in solution and under solvent-free conditions gives two types of dicarbonyl chelates with Mn–olefin or Mn–amide coordination bonds. Olefin chelates (19 and 21) were isolated for the first time, and they undergo reverse photochemical intramolecular isomerization to the amide chelates in solution and as pure liquids. For the first time, it was shown that the photochromism of cymantrene functional derivatives can be observed without the use of a solvent. Solvent-free photoisomerization and thermal isomerization between olefin and amide chelates is accompanied by a distinctive color change and can be repeated at least three times without substantial changes to the spectral parameters of these photochromic systems.
Datum: 18.07.2016


Advanced NMR Methods and DFT Calculations on the Regioselective Deprotonation and Functionalization of 1,1′-Methylenebis(3-methylimidazole-2-thione)

Depending on the temperature, the twofold deprotonation of 1,1′-methylenebis(3-methylimidazole-2-thione) (1) and the subsequent reaction with 2 equiv. of trimethylsilyl chloride (TMSCl) gives two different bis-TMS-functionalized isomers, namely, 1,1′-methylenebis(3-methyl-4-trimethylsilylimidazole-2-thione) (2) and 1,1′-methylenebis(3-methyl-5-trimethylsilylimidazole-2-thione) (3). The cyclic dimethylsilyl-bridged derivative 1,1′-methylene-5,5′-dimethylsilylenebis(3-methylimidazole-2-thione) (4) can also be obtained, corroborating the 5/5′ addition under certain conditions. All compounds have been examined by multinuclear 1D and 2D NMR experiments (1–4) together with single-crystal X-ray diffraction (3 and 4). Additionally, the dilithiated species 5 was synthesized by reacting 1 with 2 equiv. of nBuLi at ambient temperature in solution (THF). 1H and 7Li pulsed field-gradient spin-echo (PGSE) NMR, 7Li–1H heteronuclear Overhauser spectroscopy (HOESY), gradient heteronuclear multiple quantum correlation (gHMQC) and gradient heteronuclear multiple bond correlation (gHMBC) experiments showed that 5 exists as a monomeric contact ion pair (CIP) in THF solution. On the contrary, the X-ray diffraction analysis of 5 revealed a polymeric chain, which can be described as [{5(thf)2}2]∞. Quantum chemical DFT and MP2 calculations were also conducted to determine the energies required for the deprotonation of 1. These results explain the regioselective deprotonation of 1 by CIP formation depending on the temperature and fully support the results of the synthetic and spectroscopic experiments. The regioselective deprotonation and functionalization of 1,1′-methylenebis(3-methylimidazole-2-thione) is achieved through temperature control. The aggregation of the dilithiated species in the solid state and in solution is elucidated by X-ray analysis and NMR spectroscopy, respectively. Quantum chemical calculations of the deprotonation energies explain the reaction course.
Datum: 18.07.2016


Design and Photophysical Studies of Acridine-Based RuII Complexes for Applications as DNA Photoprobes

A series of new extended planar aromatic ligands based on an acridine core (dpac = dipyrido[3,2-a:2′,3′-c]acridine; dpacF2 = 7,8-difluorodipyrido[3,2-a:2′,3′-c]acridine; dpacF4 = 6,7,8,9-tetrafluorodipyrido[3,2-a:2′,3′-c]acridine) and their respective RuII complexes were synthesized and extensively studied. The photophysical and theoretical studies revealed that Ru-DPAC and Ru-DPACF2 allow emission from a 3MLCTphen/dpac excited state at 597 and 604 nm, respectively, whereas the lowest excited state for Ru-DPACF4 shifts from a bright 3MLCTphen/dpac state towards a poorly luminescent 3MLCTdpac state (λem = 609 nm) owing to the formation of hydrogen bonds with water molecules in the excited state. These complexes exhibit up to sevenfold luminescence enhancement in the presence of complementary and mismatched DNA, demonstrating a strong binding to polynucleotides. The results emphasize the interest in RuII complexes bearing acridine derivatives as DNA interacting agents as a complement to the well-known phenazine-based derivatives.RuII complexes bearing acridine-based ligands display relevant structures and photophysical behavior for their use as DNA photoprobes. Particularly, substitution of their terminal hydrogen by fluorine atoms allows tuning of the photophysical properties of the corresponding RuII complexes.
Datum: 14.07.2016


Rhodium(III) Speciation in Concentrated Nitric Acid Solutions

The interaction of rhodium(III) aqua ions with nitrate ions in 3–16 m nitric acid solutions has been studied by 103Rh and 15N NMR and Raman spectroscopy. The mononuclear complexes [Rh(H2O)6–n(NO3)n]3–n (n = 1–4) were found to be the only form of rhodium(III) existing in the solutions with the metal concentration in the range 0.2–1.3 m. The dynamics of the H2O  NO3– substitution process was studied at 80 °C. An increase in the average number of nitrate groups bonded to rhodium with increasing concentration of nitric acid was also determined. The fine crystalline salt Rb4trans-[Rh(H2O)2(NO3)4][Rh(NO3)6] was obtained by solvothermal concentration of the rhodium nitric acid solution on addition of rubidium nitrate. The structure of the salt was solved by the powder X-ray diffraction method, with monodentate coordination of nitrato ligands found for both the [Rh(NO3)6]3– and trans-[Rh(H2O)2(NO3)4]– anions.Mononuclear complexes [Rh(H2O)6–n(NO3)n]3–n (n = 1–4) have been found to be the only form of RhIII existing in concentrated nitric acid solutions. For the first time, nitrato complexes of RhIII with four and six nitrato ligands have been isolated and structurally characterized.
Datum: 14.07.2016


Magnesium and Zinc Complexes Supported by N,N,O Tridentate Ligands: Synthesis and Catalysis in the Ring-Opening Polymerization of rac-Lactide and α-Methyltrimethylene Carbonate

A series of racemic biphenyl- or binaphthyl-based aminophenols were treated with 1 equiv. of Mg[N(SiMe3)2]2 or Zn[N(SiMe3)2]2 to provide eight heteroleptic magnesium and zinc silylamido complexes (Mg, 1a–5a; Zn, 1b, 3b, 5b). Single-crystal X-ray diffraction studies on typical magnesium complex 5a and zinc complexes 1b, 3b, and 5b showed a tridentate chelating mode of the ligand and a distorted tetrahedral geometry around the metal center. All of these complexes proved to be efficient initiators for the ring-opening polymerization of rac-lactide in toluene and THF. Microstructure analysis of the resultant poly(rac-lactide) samples by homonuclear-decoupled 1H NMR spectroscopy revealed heterotacticities ranging from 0.45 to 0.69. These complexes were also applied as initiators in the polymerization of racemic α-methyltrimethylene carbonate in toluene and exhibited moderate to high regioselectivities; the most regioregular polymer was obtained with magnesium complex 4a (Xreg = 0.93).Magnesium and zinc complexes supported by biphenyl- or binaphthyl-based aminophenolate ligands efficiently initiated the ring-opening polymerization of rac-lactide (rac-LA) and α-methyltrimethylene carbonate (α-MeTMC), and gave relatively low heteroselectivities (Pr = 0.55–0.69) and high regioselectivities (Xreg = 0.81–0.93), respectively. Tol = toluene.
Datum: 14.07.2016


Yttrocene Chloride and Methyl Complexes with Variously Substituted Cyclopentadienyl Ligands: Synthesis, Characterization, and Reactivity toward Ethylene

The reaction of YCl3·3.5THF with 1 equiv. of Li(C5Me4SiMe3) afforded in high yield the ionic complex [Li(thf)4]+{[(η5-C5Me4SiMe3)YCl2]4(µ4-Cl)}– (1). The molecule of 1 consists of the tetranuclear anion {[(η5-C5Me4SiMe3)YCl2]4(µ4-Cl)}– compensated with [Li(thf)4]+ in the solid state. Reactions of compound 1 with selected lithium and potassium cyclopentadienides resulted in the formation of yttrocene chloride complexes [(η5-C5Me4SiMe3)Y(L)(µ-Cl)2M(thf)2] [M = Li, L = η5-C5H5 (2); M = Li, L = η5-C5Me5 (3); M = Li, L = η5-C5Me4SiMe2H (4); M = K, L = η5-C5Me4CH2Ph (5)]. Yttrocene chloride complexes 2–5 underwent methylation reactions to give yttrocene methyl complexes [(η5-C5Me4SiMe3)Y(L)(µ-Me)2Li(thf)2] [L = η5-C5H5 (6); L = η5-C5Me5 (7); L = η5-C5Me4SiMe2H (8); L = η5-C5Me4CH2Ph (9)]. The products of all these reactions were characterized by NMR and IR spectroscopy, and 2–5 were further studied by ESI mass spectrometry. The molecular structures of 1 and 4 were determined by single-crystal XRD. The methyl-bridged complexes 6–9 were tested as homogeneous catalysts for ethylene polymerization in the absence of cocatalysts.An ionic complex consisting of the tetranuclear anion {[(η5-C5Me4SiMe3)YCl2]4(µ4-Cl)}– and the thf-coordinated lithium cation [Li(thf)4]+ was used for the synthesis of mixed yttrocene chloride and methyl complexes containing two cyclopentadienyl ligands with different steric demands. Yttrocene methyl complexes were tested as catalysts in ethylene polymerization.
Datum: 14.07.2016


Synthesis of Homochiral CoIII– and MnIV–[2.2]Paracyclophane Schiff Base Complexes with Predetermined Chirality at the Metal Centre

The planar chiral Schiff base ligand 2, derived from (Rp)-5-formyl-4-hydroxy-[2.2]paracyclophane (FHPC) (1), was utilised to form a Λ-CoIII cis-β-octahedral metal complex 3 with complete control of the metal-centred chirality. In addition, a di-µ-oxo Λ,Λ-MnIV complex 4 was synthesised with control of both metal-centred and (P)-helical chirality.A planar-chiral Schiff base [2.2]paracyclophane-derived ligand enabled the synthesis of homochiral cis-β-octahedral CoIII and MnIV metal complexes with complete control of the metal-centred chirality, and in the case of a di-µ-oxo MnIV complex, with (P)-helical chirality.
Datum: 14.07.2016


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


Copper(I) Thiolate Heteroadamantane Cage Structures with Relevance to Metalloproteins

Cu–S heteroadamantanes are of great interest owing to their relevance to bioproteins. New copper(I) thiolate compounds with additional N-donor functions from phenanthroline ligands have been synthesised. These complexes feature heteroadamantane cage structures with minor deviations in their construction and, therefore, a strong structural relationship. Furthermore, a decanuclear copper–sulfur cluster complex was isolated and shows known structural motifs arranged in a new fashion. Metallothioneins are natural counterparts to these complexes due to their thiolate-rich and polynuclear d10 character. In addition to the structural characterisation, theoretical studies with a triple-zeta basis set have been performed to further understand the building patterns of the reported complexes and their relevance to copper-rich metalloproteins. This includes a Wiberg bond analysis and a full orbital analysis of selected heteroadamantanes to highlight the bonding interactions that connect the copper–sulfur skeletons.Herein, we present five new heteroadamantane copper(I) cluster complexes and a sixth decanuclear complex. Their structural relationship and comparability is highlighted by theoretical studies of the bonding and antibonding interactions within the molecular orbitals. These complexes show similarities to metallothioneins.
Datum: 13.07.2016


Multiple Reactivity of SnII Complexes Bearing Catecholate and o-Amidophenolate Ligands

The reactivity of tin(II) catecholate complex CatSn (1) (where Cat = 3,6-di-tert-butylcatecholate dianion) and two o-amidophenolate complexes DippAPSn (2) and PhAPSn (3) [where DippAP = 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)amidophenolate; PhAP = 4,6-di-tert-butyl-N-(phenyl)amidophenolate dianions] towards different reagents is reported. Products of the insertion of 1 and 2 into the S–S bond of tetramethylthiuram disulfide were obtained and characterised by X-ray diffraction analyses. The low temperature oxidation of complexes 1 and 2 with 2-ethoxy-3,6-di-tert-butylphenoxy radical enabled us to detect formation of paramagnetic tin(II) derivatives containing the radical-anion form of the redox-active ligand. The reaction of tin derivative 3 with Ni(CO)4 leads to substitution of one of the CO groups in the latter with the formation of a new bimetallic product.Multiple modes of reactivity for selected stannylenes bearing redox-active catecholate and o-amidophenolate ligands towards different reagents are reported.
Datum: 13.07.2016


Phase-Controlled Synthesis of Cu2SnS3 Nanocrystals: The Effect of Redox Conditions on the Initial Binary Cu2–xS Nucleation

In this work, it is shown that both pure zincblende and wurtzite structures of Cu2SnS3 (CTS) nanocrystals (NCs) have been synthesized by a facile one-spot heating-up procedure. By controlling the solvent ratios, different phase components of zincblende and wurtzite mix-phase CTS NCs were also obtained. The effect of different precursors and surfactants on the phase selectivity of CTS NCs was investigated, and a phase-controlled mechanism is proposed: the crystal structures of the resulting CTS NCs are related to the initial structure forms of the CuxS seeds, and the different phase structures are formed as a result of the initial redox conditions. When the reaction was conducted under reducing conditions, Cu2S (or Cu31S16) seeds were formed, leading to the formation of wurtzite CTS nanocrystals. When the conditions were less reducing, the initial CuS (or Cu1.84S) seeds resulted in the zincblende structure CTS nanocrystals.Different phase components of zincblende and wurtzite mix-phase Cu2SnSe3 nanocrystals (NCs) were obtained. The phase selectivity of the Cu2SnSe3 NCs is related to the initial redox conditions. Wurtzite Cu2SnSe3 NCs formed because of the Cu31S16 seeds, and the CuS seeds led to zincblende structure Cu2SnSe3 NCs.
Datum: 12.07.2016


Application of Imidazole-2-thione Substituents in Low-Coordinate Phosphorus Chemistry – Probing the Scope

A variety of (2-thioxoimidazol-4-yl)phosphanes have been synthesized with the prospect of further functionalization. Following a standard reaction protocol, P-amino (2a,b), P-chloro (3a,b), and P-hydrogeno (8a) phosphane derivatives were synthesized. Treatment of chlorophosphanes 3a,b with Lewis acids in dichloromethane/diethyl ether did not afford the expected phosphenium cation, instead ethoxyphosphane derivatives 5a,b were isolated. Treatment of secondary phosphane 8a with potassium hexamethyldisilazide afforded 2-thioxoimidazol-4-yl-substituted phosphanide derivative 10a, which was used to access dinuclear phosphanido borane 11a and tungsten complexes 12a. Furthermore, the first strong NMR evidence for P-anionic bis(imidazole-2-ylidene) 13a is provided. The first attempts to synthesize an (2-thioxoimidazol-4-yl)-substituted phosphanyl radical or its dimer, the tetrakis(2-thioxoimidazol-4-yl)-substituted diphosphane, led exclusively to tris(2-thioxoimidazole-4-yl)phosphane 14a. These compounds were fully characterized spectroscopically and the structures of 2a, 3a, 7b, 8a, 10a, 11a, and 14a were determined by single-crystal X-ray crystallography. The challenges associated with the synthesis of some of the titled compounds were studied computationally.2-Thioxoimidazole substituents have been investigated for the first time in the synthesis of low-coordinate phosphorus compounds of types I–III and revealed some surprising new features. The synthesis of some of the compounds have been studied computationally to provide further insights into some of the difficulties encountered in the syntheses.
Datum: 12.07.2016


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


First Evidence of a Water-Soluble Plutonium(IV) Hexanuclear Cluster

The singular PuIV hexanuclear cluster [Pu6(OH)4O4]12+ stabilized by 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) ligands was structurally characterized for the first time both in the solid state and in water solution by using X-ray diffraction and X-ray absorption and UV/Vis spectroscopy. The stability of this cluster in water and its high solubility over a large pH range are of upmost importance for plutonium environmental speciation with potential applications in a related migration model. The singular PuIV hexanuclear cluster [Pu6(OH)4O4]12+ is characterized in both the solid state and in water solution by using X-ray diffraction and X-ray absorption and UV/Vis spectroscopy. The stability of this cluster in water and its high solubility over a large pH range are of upmost importance for plutonium environmental speciation with potential applications in a related migration model.
Datum: 08.07.2016


Mono- and Dinuclear Rare-Earth Chlorides Ligated by a Mesityl-Substituted β-Diketiminate

The metathesis reaction of anhydrous LnCl3 (Ln = Y, Dy, Er, Sm, Yb) with the potassium salt KL [L = 2,4,6-Me3C6H2-NC(Me)CHC(Me)N-2,4,6-Me3C6H2], a mesityl-substituted β-diketiminate, is described. Dinuclear complexes with an unusual triple chlorido bridge in the molecule [LClLn(µ-Cl)3LnL(THF)] [Ln = Y (1a) and Dy (1b)] were obtained by recrystallization from a mixture of non-polar solvents (toluene/n-pentane) in low yield. In contrast, the crystallization in the presence of THF led to the isolation of mononuclear complexes [LLnCl2(THF)2] [Ln = Y (2a), Dy (2b), Er (2c), Sm (2d), Yb (2e)] in good yields. Compounds 1b and 2a–e were fully characterized, and the solid-state structures of 1a,b and 2a–c were determined by single-crystal X-ray diffraction. The magnetic properties of 2b were studied in detail.Dinuclear rare-earth metal complexes with an unusual triple chlorido bridge in the molecule [LClLn(µ-Cl)3LnL(THF)] and mononuclear complexes [LLnCl2(THF)2] were obtained by using a mesityl-substituted β-diketiminate as ligand L.
Datum: 08.07.2016


Polyhedral Bismuth Polycations Coordinating Gold(I) with Varied Hapticity in a Homoleptic Heavy-Metal Cluster

Shiny black, air-sensitive crystals of [Au(Bi8)2](AlCl4)5 were obtained from the reaction of AuCl, BiCl3, and bismuth in the ionic liquid [BMIm]Cl·4AlCl3 (BMIm = 1-n-butyl-3-methylimidazolium) at 180 °C. [Au(Bi8)2](AlCl4)5 crystallizes in the monoclinic space group P21/n. In the heavy-metal cluster [Au(Bi8)2]5+, two square-antiprismatic Bi82+ polycations coordinate the gold(I) atom in η2- and η4-mode, respectively. Quantum chemical calculations demonstrate that both Bi82+ polycations involve skeletal electrons for the donor bonding, which causes a widening of Bi–Bi distances compared with those in free Bi82+. [Au(Bi8)2]5+ is a heavy-atom cluster in which polyhedral bismuth polycations coordinate a gold(I) atom in two different modes: η2 and η4. The cationic complex was obtained by ionothermal synthesis and is a rare example of bonding interactions between gold and bismuth.
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


Intracell Hydrogen Adsorption–Transmission in a Co2P Solid Hydrogen-Storage Material

Co2P nanoparticles, obtained by a simple mechanical ball-milling treatment, have been shown to undergo a new hydrogen adsorption–transmission process called intracell Kubas-enhanced adsorption, which results in an improved hydrogen-storage capacity. It is found that in this intracell Kubas-enhanced adsorption process hydrogen is firstly adsorbed by the Co atoms in Co2P through a Co···H interaction and activated. It is then spilt over to the P atoms in Co2P accompanied by the formation of a P–H bond, which has a lower bonding energy. This adsorption–transmission process is unambiguously proved by a detailed analysis of X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), cyclic voltammetry (CV), and quantum chemical calculation results.An intracell Kubas-enhanced adsorption mechanism for improving the hydrogen-storage capacity of Co2P has been described for the first time.
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


Enhanced Antitumor Activity against Melanoma Cancer Cells by Nitric Oxide Release and Photosensitized Generation of Singlet Oxygen from Ruthenium Complexes

We have investigated the synergistic effect of nitric oxide and singlet oxygen originating from stimulated ruthenium complexes and their photodynamic action against a melanoma cancer cell line. In aqueous solution, the photosensitizer [Ru(NH3)5pz]2+ (I; pz = pyrazine) and the nitrosylruthenium complex trans-[RuCl([15]aneN4)NO]2+ (II; [15]aneN4 = 1,4,8,12-tetrazacyclopentadecane) can produce singlet oxygen and nitric oxide, respectively. The phototoxicity of complex I does not correlate with the singlet oxygen quantum yields unless it is mediated by nitric oxide release from complex II. This effect is around 70 and 50 % higher than the effect prompted by compounds I and II, respectively, in isolation in the presence of light. It was found that the number of hypodiploid cells in the melanoma cancer cells increased, which indicates that a mixture of compounds I and II induces apoptosis of tumorigenic cell lines. Both singlet oxygen and nitric oxide produced by the ruthenium complexes enhance the photodynamic efficacy in melanoma cancer cells.The synergistic effect of nitric oxide and singlet oxygen originating from Ru complexes has been used to enhance the anticancer activity against B16/F10 cancer cells. The combination of reactive oxygen and nitrogen species (RONS) resulted in a decrease of cell viability up to 40 % compared with their presence in isolation. It seems that RONS activate intracellular molecules associated with cell death.
Datum: 04.07.2016


Topological Evolution in Mercury(II) Schiff Base Complexes Tuned through Alkyl Substitution – Synthesis, Solid-State Structures, and Aggregation-Induced Emission Properties

From two series of Schiff base ligands, (E)-N-(pyridine-2-yl)(CMe=NPhR) and (E)-N-(pyridine-2-yl)(CH=NPhR) [R = H, L1a, L1b; 2-CH3, L2a, L2b; 4-CH3, L3a, L3b; 2,6-(CH3)2, L4a, L4b; 2,6-(C2H5)2, L5a, L5b; 2,6-(i-C3H7)2, L6a, L6b; 2,4,6-(CH3)3, L7a, L7b], fourteen mercury(II) complexes, namely, Hg1a–Hg7a and Hg1b–Hg7b were synthesized. Their structures were established by single-crystal X-ray diffraction, and they were physically characterized by 1H and 13C NMR spectroscopy, ESI-MS, FTIR spectroscopy, elemental analysis (EA), and powder XRD (PXRD). The crystal structures indicate that the position and type of substituent can directly influence the formation of 1D  3D supramolecular metal–organic frameworks through C–H···Cl and π–π interactions. Complexes Hg1a–Hg7a and Hg1b–Hg7b display deep blue emissions at λ = 401–428 nm in acetonitrile solution and light blue emissions at λ = 443–494 nm in the solid state. It is worth noting that Hg1a, Hg3a, Hg1b, and Hg3b exhibit good aggregation-induced emission (AIE) properties in CH3CN/H2O solutions.Two series of mercury(II) complexes (Hg1a–Hg7a and Hg1b–Hg7b) are synthesized to investigate the influence of alkyl substituents on the construction of supramolecular metal–organic frameworks (SMOFs) and photoluminescence properties. Complexes Hg1a, Hg3a, Hg1b, and Hg3b exhibit good aggregation-induced emission (AIE) properties in CH3CN/H2O solutions.
Datum: 04.07.2016


Silylosmium Anions for the Synthesis of Borylosmium(II) Complexes by Salt Elimination

Osmium anionic complexes, K[(PMe3)Os(CO)3(SiR3)] (R = Me, Et), were synthesized by deprotonation of the corresponding metal hydrides. The nucleophilicity of these compounds was demonstrated through the reaction of K[(PMe3)Os(CO)3(SiMe3)] with Cl2BDur and Br2BDur (Dur = 2,3,5,6-tetramethylphenyl) to give haloboryl complexes through a salt elimination process that is unprecedented for osmium–boron chemistry.Osmium anionic complexes, K[(PMe3)Os(CO)3(SiR3)] (R = Me, Et), are synthesized by deprotonation of the corresponding metal hydrides. The nucleophilicity of these compounds is demonstrated through the reaction of K[(PMe3)Os(CO)3(SiMe3)] with Cl2BDur and Br2BDur (Dur = 2,3,5,6-tetramethylphenyl) to give haloboryl complexes through a salt elimination process that is unprecedented for Os–B chemistry.
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


1,1- and 1,4-Addition Reactions with 3a,6a-Diaza-1,4-diphosphapentalene Containing Two-Coordinate and Formally Divalent Phosphorus

3a,6a-Diaza-1,4-diphosphapentalene (DDP) reacts with halocarbons to give addition products to one or both phosphorus atoms depending on the substrate. Chlorotriphenylmethane affords a 1,4-addition product, which slowly decomposes in solution to form the Ph3C radical and the chloro-DDP coupling product with a P–P bond. Benzyl chloride is added to one phosphorus atom to form hypervalent (trivalent, four-coordinate) phosphorus with a N···P distance (nonvalent interaction) of 2.191(2) Å. A workup of the latter with GeCl2 results in a complex salt containing the GeCl3– anion and cation with covalent N–P bonding.DDP reacts with benzyl chloride and chlorotriphenylmethane leading to 1,1- and 1,4-addition products, respectively. The 1,1-adduct of benzyl chloride contains hypervalent phosphorus showing a N···P nonvalent interaction.
Datum: 04.07.2016


The High-Pressure Polymorph of Ca4Te5O14 and the Mixed-Valent Compound Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3

A high-pressure/high-temperature experiment based on the multi-anvil technique has yielded a high-pressure (HP) modification of Ca4Te5O14 (I) from the starting materials Ca(OH)2 and TeO2. Reaction with the boron nitride crucible used in the high-pressure set-up led also to the formation of the mixed-valent TeIV,VI borate Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3 (II) as a minor phase. The crystal structures of both compounds were determined by single-crystal X-ray diffraction [I: P21/c, Z = 4, a = 11.0272(1), b = 12.0588(1), c = 10.1038(1) Å, β = 91.849(1)°, R1(F2) = 0.0317, wR2(F2) = 0.0459; II: P63/m, Z = 2, a = 9.0890(13), c = 18.731(4) Å, R1(F2) = 0.0401, wR2(F2) = 0.0867]. The principal building units of HP-Ca4Te5O14, namely [CaOx] (x = 7, 8) and TeIVO3 and TeIVO4 polyhedra, are similar to those of the ambient modification, but the structural set-up is markedly different in the two structures with an increase in density of about 6.6 %. Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3 is the first compound known so far to contain both oxotellurate and oxoborate units. The most remarkable feature of its disordered crystal structure is the centrosymmetric Te3O6 unit consisting of a TeVIO6 octahedron sharing opposite faces with two trigonal TeIVO3 pyramids. The face-sharing of TeVI and TeIV oxopolyhedra is unprecedented in the crystal chemistry of oxotellurates. In both structures I and II, the lone-electron pairs of the TeIV atoms are stereochemically active. Two new structure types have been elucidated during the high-pressure synthesis of calcium oxotellurates. The high-pressure polymorph of Ca4Te5O14 is compared with its ambient counterpart and Ca13TeVI2/3TeIV3.75O15(BO3)4(OH)3 is the first phase reported to contain both oxoborate and oxotellurate units. Face-sharing of TeVI and TeIV oxopolyhedra in the crystal structure of the latter is unprecedented in the crystal chemistry of oxotellurates.
Datum: 04.07.2016


Acid–Base Behaviour in the Absorption and Emission Spectra of Ruthenium(II) Complexes with Hydroxy-Substituted Bipyridine and Phenanthroline Ligands

Two bis(2,2′-bipyridyl)ruthenium(II) complexes bearing hydroxy-substituted diimine ligands [RuII(bpy)2(N-N)](BF4)2 (N-N = phenOH or bpyOH) have been synthesized and characterized. These complexes can be readily deprotonated under basic conditions to yield the deprotonated forms [RuII(bpy)2(N-N)](BF4) (N-N = phenO– or bpyO–). The structures of one of the complexes and its deprotonated form have been determined by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been examined. Detailed photophysical studies showed that the luminescent properties of these complexes are sensitive to the nature of the solvent media. In addition, the emission properties of these complexes exhibit a strong dependence on the pH of the aqueous medium, and hence these complexes are potentially useful as phosphorescent pH probes. A series of [RuII(bpy)2(N-N)](BF4)2 complexes bearing hydroxy-substituted diimine ligands have been synthesized and characterized. Photophysical studies showed that the luminescent properties of these complexes are sensitive to the nature of the solvent media. They also exhibit strong dependence on the pH of the aqueous medium, and hence these complexes have potential as phosphorescent pH probes.
Datum: 04.07.2016


Transition-Metal Carbonyl Complexes and Electron-Donating Properties of N-Heterocyclic-Carbene–Phosphinidene Adducts

Rhodium(I), tungsten(0), and molybdenum(0) carbonyl complexes of the N-heterocyclic-carbene–phosphinidene adducts IPr·PR [1a, R = H; 1b, R = Ph; 1c, R = Mes; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; Mes = 2,4,6-trimethylphenyl] were prepared. The reaction of 1b with [Rh(µ-Cl)(CO)2]2 afforded the dicarbonyl rhodium(I) complex cis-[(IPr·PPh)RhCl(CO)2] (2) as the major product together with the tetranuclear complex [{µ-(IPr·PPh)}2Rh4(µ-Cl)4(CO)4] (3). The latter was characterized by X-ray diffraction analysis. The tungsten pentacarbonyl complexes [(IPr·PR)W(CO)5] (4a, R = H; 4b, R = Ph; 4c, R = Mes) were isolated from the reactions of 1a–1c with [(Me3N)W(CO)5], whereas the reactions of 1a and 1b with [(thf)Mo(CO)5] (thf = tetrahydrofuran) gave the corresponding molybdenum complexes [(IPr·PR)Mo(CO)5] (5a, R = H; 5b, R = Ph). The molecular structures of the five carbonyl complexes were established by X-ray diffraction analyses. The IR spectroscopic analysis of the CO stretching frequencies of the carbonyl complexes 2, 4, and 5 revealed the strong electron-donating abilities of the phosphorus(I) ligands.A series of metal carbonyl complexes supported by N-heterocyclic-carbene–phosphinidene adducts are synthesized. The very low carbonyl stretching frequencies of these complexes in comparison with those of selected phosphines and N-heterocyclic carbenes indicate the strong electron-donating character of these newly emerging low-valent phosphorus ligands.
Datum: 04.07.2016


Alternative Precursors for the Synthesis of Binary Sb2E3 and Bi2E3 (E = S, Se, Te) Nanoparticles by the Hot Injection Method

Intramolecularly stabilized Sb(OCH2CH2NMe2)3 (1) and Bi(OCH2CH2NMe2)3 (2) readily react with (Me3Si)2S and (Et3Si)2E (E = Se, Te) at moderate temperatures (hot injection method) with elimination of the corresponding silyl ether and subsequent formation of the group 15 chalcogenides Sb2E3 and Bi2E3, which were characterized by XRD, SEM, and energy-dispersive X-ray spectroscopy (EDX). In addition, the solid-state structure of 1 was determined by single-crystal XRD.Binary antimony (Sb2E3) and bismuth chalcogenide (Bi2E3) nanoparticles were obtained by reaction of Sb(OCH2CH2NMe2)3 and Bi(OCH2CH2NMe2)3 with (R3Si)2E (E = S, Se, Te; R = Me, Et) at moderate temperatures. The reactions were studied by in situ 1H NMR spectroscopy, and the products were characterized by energy-dispersive X-ray spectroscopy, XRD, IR spectroscopy, and SEM.
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


Field-Induced Single-Ion-Magnetic Behavior of Octahedral CoII in a Two-Dimensional Coordination Polymer

Two 2D coordination polymers have been synthesized by employing V-shaped flexible terpyridine-based ligand L [L = 4′-(4-methoxyphenyl)-4,2′:6′,4′′-terpyridine] as linker and MII (M = CoII, FeII) as nodes. Structural analysis of both complexes revealed the formation of a rare [4+4] metallocyclic unit. The extension of these cyclic units into two dimensions gives rise to an interdigitated 2D sheet structure in which the methoxy group of the ligand is oriented above and below the sheet to form crests and troughs. Detailed dc and ac magnetic susceptibility measurements revealed the field-induced slow magnetic relaxation behavior of the magnetically isolated six-coordinate CoII center with easy-plane magnetic anisotropy. The effective energy barrier (Ueff) was found to be 36.9 K, which is the highest value reported so far for 2D CoII-based single-ion magnets. Two-dimensional coordination polymers have been synthesized by using 4′-(4-methoxyphenyl)-4,2′:6′,4′′-terpyridine as ligand and CoII or FeII salts. The CoII-based coordination polymer exhibits field-induced single-ion-magnet behavior.
Datum: 04.07.2016


ZnO@ZIF Core–Shell Single Crystals Formed by in Situ Conversion of ZnO Particles

We herein report the formation of two types of ZnO@ZIF core–shell single crystals through the in situ conversion of ZnO particles. The hybrid core–shell single crystals of ZIF-8 and ZIF-71 were obtained by treating 95 nm ZnO particles with 2-methylimidazole and 4,5-dichloroimidazole, respectively, under the optimized experimental conditions. The ZnO cores are spherical, caplike and noncentrally encapsulated in the ZIF crystals. The effects of the reaction solvent, ligand concentration and ZnO particle size were investigated, and the results show that the single-site heterogeneous nucleation and growth of ZIF on the template surfaces are the key to the formation of ZnO@ZIF core–shell single crystals.ZnO@ZIF-8 and ZnO@ZIF-71 core–shell single crystals can be synthesized by the in situ conversion of ZnO particles under optimized experimental conditions. The formation of these hybrid ZIF single crystals is attributed to the single-site heterogeneous nucleation and growth of ZIF on the ZnO surfaces but depends strongly on the reaction solvent, ligand concentration and ZnO particle size.
Datum: 04.07.2016


Octanuclear Silver Sulfide Cluster [Ag8(µ8-S)(µ-mimt)12](NO3)6 Containing the First Thione-Stabilized Ag8 Cube Caging a Sulfide Anion

The first thione-protected cluster [Ag8(µ8-S)(mimt)12](NO3)6 (1) (mimt = 4-methyl-1,3-imidazolidine-2-thione) was synthesized by gradual S2– release from Na2S2O3 in solution and was structurally characterized. The cluster contains a novel octanuclear Ag8 cube that cages an S2– ion at the center, and the shell is stabilized by 12 µ2-mimt ligands. Each thione ligand bridges two Ag atoms to form the cubic edges. Cluster 1 exhibits luminescent emission in the solid state at 298 K with a maximum peak at 512 nm.The first thione-protected silver sulfide cluster [Ag8(µ8-S)(mimt)12](NO3)6 (mimt = 4-methyl-1,3-imidazolidine-2-thione) is synthesized by gradual S2– release from Na2S2O3 in solution. The cluster contains an octanuclear Ag8 cube that cages an S2– ion at the center, and the shell is stabilized by 12 µ2-mimt ligands bridging two Ag atoms to form the cubic edges.
Datum: 04.07.2016


Sulfur versus Dioxygen: Dinuclear (Trisulfido)copper Complexes

In contrast to dinuclear (disulfido)copper complexes related trisulfido compounds have not been reported so far. Here we describe two new complexes of this type, [Cu2(tmpa)2S3](SbF6)2 {tmpa = tris(2-pyridylmethyl)amine} and [Cu2(tet b)2S3](OTf)2 (tet b = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane), that have been investigated and could be structurally characterized. Furthermore, the reactivity of these complexes towards dioxygen showed that the corresponding (peroxido)copper complexes formed. Depending on the stoichiometric conditions (excess of sulfur) mononuclear end-on (sulfido)copper complexes were detected spectroscopically. DFT calculations were performed and supported the experimental results. The first examples of structurally characterized (trisulfido)copper complexes (with ligands tmpa and tet b) have been synthesized and characterized. Reactivity studies and DFT calculations were performed with these complexes.
Datum: 04.07.2016


Formation of π-Cation Radicals in Highly Deformed Copper(II) Porphyrins: Implications for the Distortion of Natural Tetrapyrrole Macrocycles

Five copper(II)–porphyrin cages were synthesized with Cu ions as a template. CuII ions can be activated and stabilized as π-cation radicals in a highly deformed cage complex by electron transition from the metal ion to the π-a1u orbital of the ring. This study indicates that the activation of the unpaired electron of the CuII ion only requires the contraction of the core, because the excitation of the electron and the stability of the activated electron are related to the cage features of the molecule. The cation radical will drive the formation of CuIII ions at lower voltages, and these results aid the understanding of the roles of macrocyclic distortion and distal pockets in heme chemistry. The electronic structures of five copper(II) complexes were analyzed through electron paramagnetic resonance spectroscopy, UV/Vis spectroscopy, and electrochemical methods, and selected structural parameters were obtained directly from their crystal structures.The electronic structure of the CuII ion can be tuned through the activation of its unpaired electron under the strong compression of core in a highly ruffled porphyrin, and the activated electron can be stabilized as a π-cation radical in the cage complex. This study indicates that the activation of an electron in a CuII ion only requires the contraction of the core.
Datum: 04.07.2016


Syntheses, Structure Elucidation, and Characterization of the Borate-Nitrates RE[B5O8(OH)(H2O)x]NO3·2H2O [RE = Nd (x = 0.85), Sm (x = 0)]

The rare-earth borate-nitrates Nd[B5O8(OH)(H2O)0.85]NO3·2H2O and Sm[B5O8(OH)]NO3·2H2O have been prepared by hydrothermal synthesis. Both structures crystallize monoclinically in the space group P21/n (no. 14) with a = 642.85(2), b = 1552.58(4), c = 1070.52(2) pm, β = 90.39(1)°, and V = 1068.44(5) nm3 for the neodymium compound, and a = 644.09(3), b = 1541.99(8), c = 1050.97(5) pm, β = 90.33(1)°, and V = 1043.79(9) nm3 for the samarium variant. These compounds represent defect structures of Ce[B5O8(OH)(H2O)]NO3·2H2O. In addition to powder and single-crystal X-ray diffraction, the two novel borate-nitrates were characterized by IR and Raman spectroscopy. New borate-nitrates containing Nd3+ and Sm3+ have been synthesized hydrothermally from rare-earth nitrate hydrates and an excess of boric acid. X-ray, Raman, and IR characterizations of the new structural variants of Ce[B5O8(OH)(H2O)]NO3·2H2O are presented.
Datum: 28.06.2016


One-Pot Synthesis of Phosphanylbis(N-arylglycines) and Spontaneous Diastereoselective Lactamization of P-Alkyl Derivatives To Form Five-Membered P,N-Heterocyclic Amino Acids

The one-pot, three-component reaction of phenylphosphane with two equivalents each of 4-acetylaniline and glyoxylic acid hydrate (GAH) in diethyl ether at room temperature furnished phosphanyl-bis(glycine) 1 as a rac/meso mixture (molar ratio 7:3) whereas condensation of primary alkylphosphanes (cHexPH2, iBuPH2) with p-toluidine and GAH was followed by additional spontaneous and highly diastereoselective lactamization to form five-membered P,N-heterocyclic racemic amino acids 2 and 3. Compound 2, with three centres of asymmetry, displayed only one set of NMR signals, whereas for compound 3 one set was strongly preferred. Crystal structure analysis of 2 confirmed the presence of a racemate, with the asymmetric unit consisting of the 2R,3R,4R isomer; the molecules are linked by hydrogen bonds. The trans(eq-eq)-position of the P-cyclohexyl group towards the substituents at the adjacent C2 and C4 atoms is maintained in [D8]THF solution, as shown by small 2JPH coupling constants. Large 2JPH couplings in compound 3 hint at the opposite preference, i.e. cis orientation, of the less spatially demanding isobutyl group at phosphorus towards the C2 and C4 substituents. The trans isomers of 3 were detected only in trace amounts on the basis of characteristic PCH proton doublets with small 2JPH values. This facile route to novel trialkylphosphane-type hybrid ligands 2 and 3 may pave the way for further studies of their properties and use as ligands in transition metal compounds and catalysis. PhPH2 reacts with glyoxylic acid hydrate and a primary aniline (1:2:2) in Et2O to afford a rac/meso-mixture of corresponding phosphanyl-bis(glycine) 1. Under the same mild conditions, more P-basic primary alkylphosphanes CyPH2 and iBuPH2, undergo diastereoselective lactamization affording phosphaproline derivatives 2 and 3; the structure of 2 was amenable to X-ray crystallography.
Datum: 27.06.2016


Making Use of Obstacles: Alternative Synthetic Approaches towards Osmium(II)-Based Photochemical Molecular Devices

Two synthetic approaches towards the mononuclear complex [(tbbpy)2OsII(tpphz)]2+ (tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine; tpphz = tetrapyrido[3,2-a:2′,3′-c:3′′,2′′-h:2′′′,3′′′-j]phenazine) based on the precursor [(tbbpy)2OsIICl2] and its oxidized side product [(tbbpy)2OsIIICl2]+ are presented. The first route is analogous to that for the isostructural ruthenium complex, whereas the second strategy efficiently uses the oxidized OsIII complex under reducing conditions to obtain so-called virtual dilution, which avoids the formation of the dinuclear complex [(tbbpy)2OsII(tpphz)OsII(tbbpy)2]. Concentration-dependent NMR investigations were performed, and a dimerization constant (KD = 400) could be calculated due to π–π interactions of the tpphz moiety. Solid-state structures of all synthesized complexes show comparable bond lengths and angles with respect to each other and their ruthenium analogues. Photophysical investigations show the expected absorption in the UV/Vis region and a single emission at 758 nm for [(tbbpy)2OsII(tpphz)]2+. Electrochemical measurements show comparable behavior to the structurally similar complexes [(bpy)2M(tpphz)]2+ (M = Os, Ru). Two synthetic pathways lead to a red-light-absorbing mononuclear osmium complex incorporating a potential bridging ligand. In situ reduction of an OsIII precursor leads to facile access to the target compound owing to virtual dilution.
Datum: 27.06.2016


Rational Design of Two-Dimensional Bimetallic Wave Structures from Zigzag Chains via Site-Specific Coordination around the 2,6-Naphthalenediphosphonic Acid Motif

We report the synthesis of a novel aromatic 2,6-naphthalenediphosphonic acid (2,6-NDPA-H4) and the rational design of molecular, one-, two-, and three-dimensional structures of the resulting copper organophosphonate materials: [{Cu(terpy)}(2,6-NDPA-H3)][{Cu(terpy)}(2,6-NDPA-H3)(2,6-NDPA-H2)]·3H2O (2), [{Cu(terpy)}VO2(2,6-NDPA-H)]·H2O (4), [{Cu(terpy)}VO2(2,6-NDPA-H)] (3) and [{Cu(H2O)}(NDPA)0.5] (1). Engineering the copper coordination sphere and pH-controlled phosphonate protonation enabled the site specific dimensional evolution of CuII-organophosphonate frameworks exploiting the deprotonated phosphonate oxygen arms.The preparation of one-, two-, and three-dimensional metal–organophosphonate frameworks from a V-shaped molecular precursor is reported.
Datum: 27.06.2016


2,5-Norbornadiene C–C Coupling Reactions Mediated by Iridium Complexes

The treatment of [{Ir(µ-Cl)(cod)}2] (cod = 1,5-cyclooctadiene) with 2,5-norbornadiene (nbd) in the presence of triethylphosphane under an atmosphere of ammonia afforded the cation complex [Ir(κC,κC-C21H24)(NH3)3(PEt3)]Cl (1a) and complex [Ir(κC,κC-C21H24)Cl(NH3)2(PEt3)] (1b), the structures of which include a novel seven-membered iridacycle formed by three half-coupled nbd molecules. The formation of the metallacycle has been found to occur through several steps. First, the nbd displaces the cod in [{Ir(µ-Cl)(cod)}2] to give the IrIII chloro-bridged complex [{Ir(κC,κC-C14H16)(µ-Cl)(η4-C7H8)}2] (2), which bears a η4-C=C-coordinated nbd and a five-membered iridacycle formed by two half-coupled nbd moieties. Further reaction with PEt3 induces the C–C coupling between the iridacycle and the coordinated nbd to give the chloro-bridged complex [{Ir(κC,κC-C21H24)(µ-Cl)(PEt3)}2] (4). Finally, 4 reacts with gaseous ammonia to split the chloro bridges and form species 1a and 1b. Also, complex 2 was found to react with several donor ligands to afford the corresponding mononuclear adducts [Ir(κC,κC-C14H16)Cl(η4-C7H8)(L)] [L = py (5), NH3 (6), PMe2Ph (7), tBuNC (8)]. The X-ray molecular structures of 5, 7 and 8 show the presence of a five-membered iridacycle, but their stereochemistries differ by virtue of the relative locations of the respective added ligand. Five- and seven-membered iridacycles have been prepared by sequential C–C bond-forming reactions between 2,5-norbornadiene molecules.
Datum: 27.06.2016


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


23- and 27-Membered Macrocyclic Diorganotin(IV) Bis-dithiocarbamates: Synthesis, Spectroscopic Characterization, DFT Calculations, and Physicochemical Analysis as Anion Receptors

Four secondary diamines with aromatic spacer groups derived from α,α′-dibromo-p-xylene and 4,4′-bis(chloromethyl)-1,1′-biphenyl have been transformed into bis-dithiocarbamate ligands and each combined with dimethyl-, di-n-butyl-, and diphenyltin(IV) dichloride to yield a total of 12 mononuclear diorganotin(IV) bis-dithiocarbamate complexes with six-coordinate metal coordination geometries and either 23- or 27-membered macrocyclic structures. The products were fully characterized by IR and NMR (1H, 13C, 119Sn) spectroscopy and high-resolution ESI+-TOF mass spectrometry. A representative selection of the macrocyclic complexes was further examined by DFT computational studies and the relative binding energies of the cis and trans isomers of the different diorganotin complexes were calculated and compared. Additionally, four possible conformations of the trans isomers were analyzed. With the purpose of examining whether the complexes can be applied to the recognition of anions, five macrocycles were selected based on criteria that allowed the influence of the aromatic spacer group, the N substituent of the dithiocarbamate ligand, and the organic groups attached to the metal center on the recognition properties to be explored. Among the NMe4+X– salts (X– = F–, Cl–, Br–, I–, NO3–, HSO4–, and CH3COO–) examined, the diorganotin complexes were sensitive to fluoride and carboxylate anions.Organotin-based macrocycles suitable for the selective recognition of fluoride and acetate have been structurally modified at three different sites to explore the effects of variations of the molecular configuration and conformation.
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


Vanadium Polyoxoanions within Coordination Polymers Based on a Macrocyclic Nickel Complex: Structural Diversities and Single-Crystal to Single-Crystal Transformation

Five three-dimensional (3D) coordination polymers, {(NiL)[(NiL)(V16O42)]}n·2nH2O (1), [(NiL)3(VO3)6]n·5nH2O (2), [(NiL)3(V6O18)]n·7nH2O (3), [(NiL)3(V8O23)]n (4), and [(NiL)4(V10O29)]n (5), have been obtained by the reaction of the macrocyclic nickel complex [NiL](ClO4)2 (L = 1,4,8,11-tetraazacyclotetradecane) with NH4VO3 under different conditions. Single-crystal X-ray diffraction analyses revealed that the [VO3]– anion assumes diverse species and structures in these five coordination polymers, including the [V16O42]n4n– sheet, [V6O18]6– ring, [VO3]nn– chain, [VO3]nn– sheet, and [V10O29]n8n– chain. The [V16O42]n4n– sheets, [V6O18]6– rings, [VO3]nn– chains, [VO3]nn– sheets, and [V10O29]n8n– chains are linked together through [NiL]2+ bridges to form the 3D frameworks of 1–5. The single-crystal to single-crystal transformation between 2 and desolvated 2 was successfully realized. Electrochemical measurements indicate that 2 and 4 are potential catalysts for water splitting.Five coordination polymers have been constructed from a macrocyclic NiII complex and vanadium polyoxoanions. The vanadium polyoxoanions assume diverse structures, namely the [V16O42]n4n– sheet, [V6O18]6– ring, [VO3]nn– chain, [VO3]nn– sheet, and [V10O29]n8n– chain. Electrochemical measurements indicate that two of the coordination polymers are potential catalysts for water splitting.
Datum: 22.06.2016


Anchoring Cytochrome b562 on a Gold Nanoparticle by a Heme–Heme Pocket Interaction

Gold nanoparticles immobilized on a gold electrode surface were modified with a heme moiety through gold–sulfur bonds and then treated with apocytochrome b562 (apoCYT) to yield a reconstituted protein on the gold nanoparticles. Immobilization of apoCYT on the surface of the AuNP-modified electrode was confirmed by the charge-transfer resistance value RCT determined using alternating-current electrochemical impedance spectroscopy. The N 1s and Fe 2p peaks in the X-ray photoelectron spectrum support the reconstitution of the heme moiety on the surface of the AuNP electrode. The hemoprotein-immobilized electrode exhibits a ten-fold enhanced electrochemical response relative to the protein immobilized directly on the gold electrode.Gold nanoparticles were immobilized on a gold electrode surface. Apocytochrome b562 was then immobilized on the surface of the AuNP-modified electrode through a heme–heme pocket interaction. The hemoprotein-immobilized electrode exhibited a ten-fold enhanced electrochemical response relative to the protein immobilized directly on the gold electrode.
Datum: 22.06.2016


Nickel Nanoparticles Supported on CMK-3 with Enhanced Catalytic Performance for Hydrogenation of Carbonyl Compounds

Ordered mesoporous carbon materials are becoming increasingly important in catalysis applications due to their advantageous stability and surface properties. In this paper, we report a replication of the synthesis of mesoporous carbon CMK-3 using SBA-15 as a silica template. Ni/CMK-3 was prepared by incorporating Ni particles formed inside the pores of CMK-3 by impregnation of nickel nitrate and subsequent hydrogen reduction. The prepared Ni/CMK-3 has a large surface area and a very small nickel nanoparticle size (1 nm) with the aim of achieving high performance in catalytic hydrogenation reactions. Moreover, we demonstrate that CMK-3 has a higher stability than that of SBA-15 during the hydrogenation reactions of acetophenone derivatives.Ni/CMK-3 was prepared by incorporating Ni particles formed inside the pores of CMK-3 by impregnation of nickel nitrate and subsequent hydrogen reduction. The prepared Ni/CMK-3 has a large surface area and a very small nickel nanoparticle size (1 nm) with the aim of achieving high performance in catalytic hydrogenation reactions.
Datum: 22.06.2016


Synthesis of a Silylated Phosphorus Biradicaloid and Its Utilization in the Activation of Small Molecules

Reduction of silylated 1,3-dichloro-1,3-diphospha-2,4-diazane, [ClP(µ-NHyp)]2 [Hyp = Si(SiMe3)3], with activated magnesium in dimethoxyethane allowed the isolation and full characterization of the first stable silylated biradicaloid, [P(µ-NHyp)]2. The oxidation of [P(µ-NHyp)]2 with selenium and sulfur was studied. Activation of molecules bearing double bonds was achieved in the reaction with acetone and carbon disulfide, yielding heteroatom cage compounds.Silylated 1,3-dichloro-1,3-diphospha-2,4-diazane, [ClP(µ-NHyp)]2 [Hyp = Si(SiMe3)3], was reduced with activated magnesium to afford the silylated biradicaloid [P(µ-NHyp)]2, which was isolation and fully characterized. The activation of molecules bearing single and double bonds with [P(µ-NHyp)]2 was studied, yielding heteroatom cage compounds.
Datum: 22.06.2016


Iridium(III) Complexes of Terpyridine- and Terpyridine-Analogous Ligands Bearing Sugar Residues and Their in vitro Activity

A series of terpyridine- and terpyridine-analogous ligands bearing sugar moieties (glucose, galactose) attached through different glycosidic bonds (S-glycosides, O-glycosides) and their iridium(III) complexes was synthesized and characterized. Their in vitro cytotoxicity was investigated, and one iridium complex with significant activity could be identified and studied in more detail. Dose-dependent inhibition of cell growth was achieved at low concentrations (5 µm). For reduction of proliferation by 50 % (ID50) the necessary concentration was 0.5 µm. The induction of apoptosis could be verified by flow-cytometric determination of DNA fragmentation in BJAB cells after 72 h. Apoptosis induction of the iridium complex in drug-resistant cells was tested with modified BJAB and Nalm-6 cells and their nonresistant strains. The complex was able to induce apoptosis in 50 % of cells (AC50) in concentrations of 30 µm in BJAB cells, 20 µm in Nalm-6 cells, 10 µm in resistant Nalm-6 cells, and 5 µm in resistant BJAB cells. Unspecific cell death was excluded by LDH-release assay. A series of terpyridine and terpyridine-analogous ligands bearing sugar moieties attached by different glycosidic bonds and their IrIII complexes was synthesized and characterized. Studies on cell viability, selectivity, drug resistance in vitro, and the apoptosis mechanism were performed. The results revealed enhanced activity of a complex bearing acetylated thioglucose.
Datum: 22.06.2016


Tri- and Pentanuclear Complexes Derived from Manganese(III) Schiff Base and Hexacyanoferrate(III) Building Blocks

A tri- and a pentanuclear cyanido-bridged complex based on manganese(III) Schiff base and hexacyanoferrate(III) units, namely, [{Mn(naphtmen)}2{Fe(CN)6}][Mn(naphtmen)(CH3OH)2]2ClO4·5CH3OH·H2O [1; naphtmen2– = N,N′-(1,1,2,2-tetramethylethylene)bis(naphthylideneiminato) dianion] and [{Mn(naphtmen)}4{Fe(CN)6}]ClO4 (2), were synthesized and structurally characterized by X-ray single-crystal diffraction. The structural analyses show that 1 consists of linear trinuclear clusters of [{Mn(naphtmen)}2{Fe(CN)6}]– anions, which are further linked into one-dimensional chains by the out-of-plane biphenolate bridges. In 2, magnetically isolated cyanido-bridged pentanuclear {[Mn(naphtmen)]4[Fe(CN)6]}+ cations were obtained. The temperature-dependent magnetic susceptibilities indicate that the exchange interactions between the FeIII and MnIII ions through the cyanido bridges are ferromagnetic in 1 and 2. The magnetic fittings for 1 and 2 gave magnetic coupling constants JMnFe = 6.68 and 4.31 cm–1, respectively. Complex 2 exhibits a clear frequency-dependent alternating-current (AC) magnetic susceptibility below 3.5 K, which is due to single-molecule magnet behavior with Ueff = 23.4 cm–1 and τ0 = 7.5 × 10–10 s.Two cyanido-bridged complexes are synthesized from the same [Mn(SB)(H2O)]+ (SB = Schiff base) and hexacyanoferrate(III) reactants. The first complex consists of cyanido-bridged linear trinuclear [{Mn(SB)}2{Fe(CN)6}]– anions, which are further linked into 1D chains by biphenolate bridges. The second complex is a cyanido-bridged pentanuclear complex, which behaves as a single-molecule magnet.
Datum: 22.06.2016


Remarkable Ability of the Benzylidene Ligand To Control Initiation of Hoveyda–Grubbs Metathesis Catalysts

The structure of the chelating benzylidene ligand offers the unique ability to control the initiation of Hoveyda–Grubbs metathesis catalysts. Apart from steric and electronic effects acting on the step involving opening of the chelate ring, changes related to the following ligand-exchange process may also play a critical role. Our mechanistic model reveals that ligands substituted at the 6-position of the benzylidene ring enter the metathesis cycle in a nonoptimal chelating conformation, and thus the coordination number of the ruthenium center transiently increases to six (associative mechanism). In effect, the synthesis and initiation of the catalysts becomes difficult, and the energy barrier of the ligand-exchange process is controlled by the structure of the coordinating OR group. Moreover, we explain how isomeric naphthalene ligands affect the catalytic performance by an indivisible combination of steric and π-electron delocalization effects.Initiation of Hoveyda–Grubbs metathesis catalysts requires opening of the chelate ring, followed by ligand exchange in the initial turnover of the metathesis cycle. Our studies reveal that substitution at the 6-position of the benzylidene ring influences the latter process and shifts the complexes to the latent systems (Mes = 2,4,6-trimethylphenyl).
Datum: 22.06.2016


Photophysical Characterization and Recognition Behaviour of a Bis(dansylated) Polyoxometalate

The bis(dansylated) polyoxometalate (nBu4N)4[γ-SiW10O36{(Me2N)C10H6SO2NH(CH2)3Si}2O] has been investigated to establish the impact of the inorganic polyanionic domain on the photophysical behaviour of the appended dansyl chromophore. The interactions of this molecular hybrid with Lewis acids (lanthanide cations) and with an aromatic cationic molecule (N,N′-2,7-didecyldiazapyrenium) have also been monitored by multiple techniques, including spectrofluorimetry, Z-potential, 1H NMR spectroscopy, transmission electron microscopy. The different spectral behaviour, coupled with the morphological evolution of the resulting nanostructures, highlights the capability of the hybrid polyoxometalate to interact, acting as a ditopic receptor, with different chemical substrates.A bis(dansylated) polyoxotungstate has been characterized to highlight the photophysical interplay between its two functional domains: a tweezer-like motif, defined by the dansyl units, and the polyanionic inorganic scaffold. The two subunits shape a ditopic receptor, being able to interact with lanthanide ions and with cationic organic chromophores, which trigger different spectral and morphological responses
Datum: 22.06.2016


Electrostatic Properties of N-Heterocyclic Carbenes Obtained by Experimental Charge-Density Analysis of Two Selenium Adducts

High-resolution X-ray diffraction data and Hansen–Coppens multipole formalism have been used to obtain the charge density distribution in two selenium adducts with the N-heterocyclic carbenes 1,3-dimesitylimidazolidin-2-ylidene (1) and 1,3-dimesityl-4,5-dioxoimidazolidin-2-ylidene (2). Application of Bader's quantum theory of atoms in molecules and calculation of the atomic charges by integration of the experimental electron density over the atomic basins showed that the main electrostatic difference between the Se adducts is in the significantly different accumulation of electron density in their C(carbene)–Se fragments (–0.10 vs. +0.30 e in 1 and 2). Deformation electron density features along the C–Se bond and topological values at the bond critical point indicate that this bond has π character in both compounds but it is more pronounced in the case of 2. This is in agreement with stronger C–N bonds and a larger N–C–N angle in 1. The experimental charge density distribution also clearly indicates the important role of the N-mesityl substituent as an electron-donating group, which increases the electron density in the imidazole ring thus contributing to the electronic stabilization of the carbene C atom. Because the N-mesityl substituents donate similar amounts of electron density in both molecules (0.75 and 0.64 e in 1 and 2), it was concluded that the decisively different electronic properties of the two NHCs have to be attributed to their different backbone structures. High-resolution X-ray diffraction experiments (100 K) have been used to investigate and quantitatively compare the electron density distribution in two carbene adducts of selenium.
Datum: 22.06.2016


Microporous Metal–Organic Frameworks Based on Zinc Clusters and Their Fluorescence Enhancements towards Acetone and Chloroform

Two microporous metal–organic frameworks (MOFs) based on zinc clusters, that is, [Zn3(BDC)2(HBDC)2]·2DMA·4CH3OH·2H2O (1; H2BDC = 1,4-dicarboxybenzene, DMA = N,N-dimethylacetamide) and [(CH3)2NH2]2[Zn7(µ4-O)2(NDC)6]·DMF·H2O (2; H2NDC = 1,4-naphthalenedicarboxylic acid, DMF = N,N-dimethylformamide), were synthesized by a solvothermal method. Both compounds possess three-dimensional porous skeletons with square channels and exhibit interesting blue fluorescence. Compound 1 consists of trinuclear ZnII building units bridged by both BDC2– and HBDC– ligands, which results in the formation of a 2,8-connnected topological net (hex). Compound 2 features another 2,8-connected topological net (bcu) that is constructed by eight-connected Zn7(µ4-O)2 clusters and two-connected NDC2– ligands. The solid-state and solvent-dependent fluorescence of the two MOFs revealed that 1 and 2 showed fluorescence enhancement effects in the presence of acetone and chloroform, respectively, which thereby demonstrates their potential as fluorescent sensors for selective sensing towards acetone and chloroform.Two fluorescent metal–organic frameworks constructed with d10-configured metal clusters (i.e., Zn3 and Zn7O2) and organic carboxylic acid ligands (i.e., 1,4-dicarboxybenzene and 1,4-naphthalenedicarboxylic acid) are synthesized. They show interesting fluorescence enhancement effects towards acetone and chloroform, respectively.
Datum: 20.06.2016


A Size-Dependent Analysis of the Structural, Surface, Colloidal, and Thermal Properties of Ti1–xB2 (x = 0.03–0.08) Nanoparticles

We report the size-dependent structural, surface, colloidal, and thermal properties of the well-known refractory material titanium diboride prepared at the nanoscale by a size-controlled inorganic molten-salt technique. A combined analysis of the powder X-ray diffraction data through a modified Williamson–Hall plot, a size–strain plot, and Rietveld fitting methods indicates that TiB2 nanocrystals with average crystallite sizes smaller than D ≈ 22 nm prefer to form defects at the titanium site rather than experience strain. The resulting composition is Ti1–xB2 [x = 0.03(1)–0.08(1)]. The size-induced defect formation is accompanied by anisotropic lattice contraction that decreases primarily the cell parameter c. Transmission electron microscopy revealed that the nanocrystals are embedded in an amorphous matrix. A comparison between the electron spin resonance spectra of bulk and nanosized samples indicated that only the nanosized samples yield observable signals. This signal is associated with unpaired electrons trapped in the boron–oxygen species that surround the Ti1–xB2 nanocrystals. These species provide stability to the Ti1–xB2 nanocrystals in aqueous dispersions, as evidenced by electrokinetic measurements. Upon heating under an Ar atmosphere, the boron–oxygen species evaporate from ca. 1000 °C, and the Ti vacancies in the interior nanocrystalline core vanish. TiB2 nanocrystals show excellent chemical stability against decomposition up to 1500 °C. We report the size-dependent structural, surface, colloidal, and thermal properties of the well-known refractory material titanium diboride prepared at the nanoscale by a size-controlled inorganic molten-salt technique.
Datum: 20.06.2016


A Computational Approach to Predicting Ligand Selectivity for the Size-Based Separation of Trivalent Lanthanides

Reprocessing of high-level waste is a key step in advancing sustainable energy systems. The development of efficient chelating agents for trivalent f-block metal ions is essential for increasing the efficiency of nuclear-waste remediation and extractive hydrometallurgy of rare-earth elements. Although computer-aided screening could lead to a more rapid discovery of superior ligands, an accurate theoretical description of the solvation effects for trivalent metal ions is currently a stumbling block in qualitative predictions for selectivity trends along the lanthanide series. In this work, we propose a robust model to describe the differential effect of solvation in the competitive binding of a ligand with lanthanides by including weakly coordinated counterions in the complexes of more than a +1 charge. The success of this approach in quantitatively reproducing aqueous selectivities demonstrates its potential for the design and screening of new ligands for efficient size-based separation.We report an approach based on quantum chemical calculations that achieves high accuracy in predicting aqueous-phase selectivity across the lanthanide series. Quantitative agreement with experiment demonstrates the potential of the method for accelerated computer-aided discovery of superior ligands for selective lanthanide ion complexation.
Datum: 20.06.2016


One-Pot Synthesis of Ordered Mesoporous NiSiAl Oxides for Catalyzing CO2 Reforming of CH4

Ordered mesoporous NiSiAl composite oxides with an amorphous phase were prepared by an improved evaporation-induced self-assembly strategy. The silica was distributed homogeneously in the mesoporous skeleton and improved the ordered mesoporous structure of NiAl. Catalytic tests toward the CO2 reforming of CH4 indicated that the NiSiAl exhibited higher catalytic activity and stability over 100 h at 700 °C than NiAl. The enhanced performance results from the high thermal stability induced by Si doping, which hinders the Al2O3 phase transformation from amorphous to γ-Al2O3; therefore, the uniform dispersion of the Ni nanoparticles is retained owing to the confinement effect of the ordered mesopores. The stabilized Ni nanoparticles reinforced the resistance of the catalyst to carbon deposition and, thus, boosted its durability. Notably, even under more stringent conditions (750 °C, 200 h), NiSiAl-0.10 retained its amorphous Al2O3 structure and showed outstanding durability, almost without any deactivation.Ordered mesoporous NiSiAl oxide is prepared by an improved evaporation-induced self-assembly strategy. The silica doping improves the retention of ordered mesopores and the amorphous NiAl phase; this permits the uniform dispersion of the active Ni nanoparticles and, thus, decreases the amount of deposited carbon and improves the catalytic stability for the CO2 reforming of CH4.
Datum: 20.06.2016


Spin Modulation in Highly Distorted FeIII Porphyrinates by Using Axial Coordination and Their π-Cation Radicals

A series of five-coordinate FeIII octaaryltetraphenylporphyrins [FeIII(por)(X)] (X = Cl, I, I3, ClO4, or SO3CF3) and their 1 e–-oxidized complexes [FeIII(por·)(X)(Y)] (X = Cl, I, ClO4, or SO3CF3; Y = SbCl6, I3, ClO4, or SO3CF3) have been synthesized and characterized. The electronic structures have been confirmed by using UV/Vis, IR, 1H NMR, EPR, and Mössbauer spectroscopy as well as signal-crystal X-ray diffraction studies. The neutral five-coordinate complexes exhibit spin states ranging from essentially pure high spin (S = 5/2 with X = Cl), admixed intermediate spin (S = 5/2, 3/2 with X = I) to an essentially pure intermediate spin (S = 3/2 with X = I3, ClO4, and SO3CF3) depending upon the axial ligand field strength. The average Fe–Np length decreases with decreasing axial ligand strengths, Cl < I < ClO4 < I3 ≈ SO3CF3, which happens to be the order of increasing contributions of the intermediate-spin state to the complexes. DFT calculations demonstrate a dramatic change in the orbital energy levels upon changing the axial ligand strength. Upon 1 e– oxidation, the high-spin chloro complex forms the five-coordinate high-spin FeIII porphyrin π-cation radical, whereas the essentially pure intermediate perchlorato, triflato, triiodo iron(III) porphyrinates produce the corresponding six-coordinate high-spin iron(III) porphyrin π-cation radicals. The oxidation also induces larger separation between the up- and down-field shifted methylene resonances in the 1H NMR spectra owing to the presence of the π-cation radical.A series of five-coordinate FeIII octaaryltetraphenylporphyrins with varying axial ligand field strength and their 1 e–-oxidized complexes have been synthesized and characterized. The molecular structures and their spectroscopic properties including metal spins have been scrutinized.
Datum: 15.06.2016






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