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European Journal of Inorganic Chemistry - Current Research Articles

Current research articles: Inorganic Chemistry

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European Journal of Inorganic Chemistry - published by Wiley-VCH

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.

Current articles of the journal:

Poly-Boron, -Silicon, and -Gallium Lewis Acids by Hydrometallation of 1,5- and 1,8-Dialkynylanthracenes

1,5-Dialkynylanthracenes and 1,8-dialkynylanthracenes have been functionalised by a series of hydrometallation reactions, namely, hydrosilylation, hydroboration and hydrogallation. Nine anthracene-based Lewis acidic compounds with a semiflexible organic framework bearing SiCl3, SiCl2Me, SiClMe2, B(C6F5)2 and GaCl2 substituents were obtained. In all cases, the substrate could be functionalised twice, and bidentate Lewis acids were obtained. By using Piers' borane [HB(C6F5)2], a fourfold-substituted anthracene species functionalised with four extremely electronegatively substituted boron atoms could be generated in quantitative yield. All of the poly-Lewis acids were characterised by multinuclear NMR spectroscopy and, in part, by mass spectrometry and X-ray diffraction experiments. A series of B-, Si- and Ga-containing poly-Lewis acids were synthesised by converting 1,5- and 1,8-dialkynylanthracene derivatives in hydrometallation reactions. Some of the compounds reacted with diethyl ether, which demonstrates the variable behaviour of the Lewis acidic compounds towards Lewis basic molecules.

Posted on 25 July 2014 | 11:10 am

Synthesis of Trinuclear Heterobimetallic Cyanido-Bridged Complexes from the Reaction of [MnI(CN)(CO)(tBuNC)4] with Transition-Metal Chlorides

The reaction of [Mn(CN)(CO)(tBuNC)4] with MnCl2·4H2O, FeCl3·9H2O, NiCl2·6H2O, and CuCl2·2H2O, respectively, led to the formation of trinuclear heterobimetallic complexes that comprised two manganese moieties, with each coordinating the corresponding metal chloride entities through cyanide bridges. The mixed-valence trinuclear MnI–CN–MnII–NC–MnI complex as well as the MnI–CN–NiII–NC–MnI derivative have been characterized by X-ray structure analyses. In the case of the copper and iron compounds that exhibit easily reducable central metal ions, intramolecular electron transfer from manganese(I) to copper(II) or iron(III), respectively, is shown by the presence of metal-to-metal charge-transfer (MMCT) bands as well as by EPR spectroscopy. Moreover, the iron complex shows a subsequent disproportionation, which was demonstrated by the isolation and crystallographic characterization of the reduced species with two manganese(I) complex units coordinating one FeIICl2 moiety. The reaction of [Mn(CN)(CO)(tBuNC)4] with transition-metal chlorides led to the formation of cyanide-bridged trinuclear coordination compounds. If CuII or FeII was used as the central metal atom, intramolecular electron transfer (M = Cu, Fe) and disproportionation processes (M = Fe) were observed and investigated by UV/Vis and EPR spectroscopy and X-ray crystallography.

Posted on 24 July 2014 | 12:10 pm

Coordination Cluster Analogues of the High-Spin [Mn19] System with Functionalized 2,6-Bis(hydroxymethyl)phenol Ligands

A series of 2,6-bis(hydroxymethyl)-4-R-phenol ligands (H3LR; R = H, F, Cl, Br, I, Ph, NH2, NO2, SMe) have either been newly synthesized or the existing syntheses have been significantly improved to investigate ligand-functionalized analogues of the previously published coordination cluster [MnIII12MnII7(?4-O)8(?3-N3)8(HLMe)12(MeCN)6]Cl2·10MeOH·MeCN (1) with S = 83/2. The crystal structures and magnetic properties of three such Mn19 clusters, namely, [MnIII12MnII7(?4-O)8(HLH)12(?3-Cl)7(?3-OMe)(MeOH)6]Cl2·16H2O·10MeOH·MeCN (3), [MnIII12MnII7(?4-O)8(HLI)12(?3-N3)8(MeOH)6](O2CH)2·16MeOH·10MeCN (4) and [MnIII12MnII7(?4-O)8(?3-Cl)7.7(?3-OMe)0.3(HLSMe)12(MeOH)6]Cl2·27MeOH (5) are reported and compared to those of the parent cluster. When these ligands are functionalized with substituents of moderate electronegativity, it is possible to synthesize Mn19 analogues; however, when such ligands bear highly electron-donating (amino) or -withdrawing (nitro) substituents, the Mn19 analogues are no longer accessible. The Mn19 cluster framework is both magnetically and structurally robust with respect to the electron-donor/acceptor characteristics of the ligand substituent; therefore, the Mn19 system is an excellent platform for peripheral chemical engineering. The robustness of the inorganic {MnIII12MnII7(?4-O)8} core of Mn19 systems with variously functionalized encapsulating ligands is demonstrated by the invariance of the record S = 83/2 spin state. Chemical modification aimed towards attaching the molecule to various substrates does not interfere with the electronic structure.

Posted on 24 July 2014 | 12:10 pm

Optimal-Temperature-Based Highly Efficient NiS Counter Electrode for Quantum-Dot-Sensitized Solar Cells

Metal sulfide electrodes were compared to a conventional platinum (Pt) counter electrode (CE) in quantum-dot-sensitized solar cells (QDSSCs), in which they were used to improve the short circuit current, fill factor, and conversion efficiency (?). We deposited optimal-temperature-based nickel sulfide (NiS) thin films on a fluorine-doped tin oxide (FTO) substrate by a facile chemical bath deposition method and successfully employed them as a highly efficient CE for QDSSCs. The obtained NiS thin-film nanoparticles exhibit high electrocatalytic performance and fast mass transfer rates toward the polysulfide electrolyte. Under the illumination of one sun (100 mW?cm–2), the QDSSC with a NiS CE produces a higher ? of 3.30?%, which is much higher than that of a Pt CE (1.89?%). Cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization measurements were performed to investigate the electrocatalytic activity of the NiS CE toward polysulfide electrolyte. In quantum-dot-sensitized solar cells, nickel sulfide is a highly efficient catalyst by reducing the redox species that mediate the reduction of the sensitizer after electron injection. The catalytic activity of the NiS counter electrode depends on the deposition temperature. This is supported by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and Tafel polarization measurements.

Posted on 24 July 2014 | 12:10 pm

Inclusion of an Iodine Molecule in a Tiara-Like Octanuclear Palladium Thiolate Complex

An iodine molecule was successfully inserted into the inner cavity of a tiara-like octanuclear palladium thiolate complex, [Pd(?-SCH2CO2Me)2]8. The included iodine molecule coordinated weakly to six palladium atoms in both linear and bent modes, as confirmed by X-ray crystallography and DFT calculations. The inclusion complex reacted with an excess amount of I2 to produce a disulfide, which was accompanied by decomposition of the tiara ring. An iodine molecule is successfully inserted into the inner cavity of a tiara-like octanuclear palladium thiolate complex, [Pd(?-SCH2CO2Me)2]8. The included iodine molecule coordinates weakly to six palladium atoms in both linear and bent modes. The inclusion complex reacts with an excess amount of I2 to produce a disulfide, which is accompanied by decomposition of the tiara ring.

Posted on 23 July 2014 | 8:20 am

Photoluminescence of Zinc Complexes: Easily Tunable Optical Properties by Variation of the Bridge Between the Imido Groups of Schiff Base Ligands

A series of organic–metal chelate complexes of symmetric tetradentate Schiff base ligands derived from salicylaldehyde and 2-hydroxy-1-naphthaldehyde were designed and investigated. The combination of five nonconjugated flexible spacers and five conjugated rigid spacers with four salicylaldehyde derivatives provided a series of forty complexes. The series of blue to red photoluminescent complexes was investigated by UV/Vis absorption and luminescence spectroscopy in solution and in the solid state as well as cyclic voltammetry. The nature of the bridge in the ligand scaffold was determined to be the main parameter that influences the absorption and the emission color of the investigated zinc(II) complexes. Forty Schiff base zinc(II) complexes have been designed and studied for their photoluminescence properties. Interestingly, the nature of the diamine spacer in the ligand is the unique factor that influences the optical properties of the complexes.

Posted on 23 July 2014 | 8:20 am

X-ray Crystallographic Analysis of a Tailor-Made Bis(phthalocyaninato)-TbIII Single-Molecule Magnet as a Fundamental Unit for Supramolecular Spintronic Devices

The single-crystal X-ray diffraction analysis of the title compound, the pyrene-substituted unsymmetrical bis(phthalocyaninato)terbium(III) Single-Molecule Magnet (SMM) [Pc–Tb–Pc*]0 (1) (Pc = dianion of phthalocyanine, P* = dianion of phthalocyanine decorated with six flexible hexyl chains and one 4-pyren-1yl-butoxy group), was carried out. Both phthalocyaninato ligands in 1 are distorted from planarity and, therefore, adopt a biconcave shape. Effective ?–? interactions between the molecules lead to the formation of head-to-tail ? dimers. These dimers are stacked in the crystal, forming adjacent, parallel columns, the axes of which are tilted by 30° with respect to the C4 axes of the macrocycles. Herein, we also report the synthesis and characterization of the new isostructural Dy (compound 2) and Ho (compound 3) analogues of 1. The structure of a [Pc–Tb–Pc*] SMM was determined. A single-crystal X-ray diffraction analysis revealed an effective intermolecular ?–? interaction leading to the formation of ? dimers, which are stacked with neighboring dimers in parallel columns with an axis tilted by 30° with respect to the C4 axis of individual molecules. Isostructural Dy and Ho analogues were synthesized and characterized.

Posted on 23 July 2014 | 8:20 am

Compositionally Controlled Self-Assembly of Hierarchical Pd–Ni Bimetallic Chains

Magnetic Pd–Ni bimetals with various compositions were synthesized by a one-pot reaction, in which chain-like Pd–Ni bimetals formed through the self-assembly of Pd–Ni nanoparticles. The self-assembly behaviour of the Pd–Ni bimetals gradually changes with the changes in composition. The Pd–Ni nanoparticles form simple chains at lower Pd content, while the Pd–Ni bimetals take on a beads-on-string structure composed of sphere-shaped Pd–Ni-nanoparticle assemblies at higher Pd content. Magnetic hysteresis loops show that Ni-rich assemblies have a higher saturation magnetization than Pd-rich assemblies. The formation mechanism for these Pd–Ni assemblies is proposed, in which the self-assembly behaviours are controlled by the competition of the surfactant interaction and the magnetic dipole interaction. The catalytic activity and selectivity of the hydrogenation of acetophenone over these Pd–Ni bimetals depend on their compositions. The self-assembly of Pd–Ni bimetals with various compositions was performed by a one-pot reaction. The formation mechanism for these assemblies is proposed, in which the self-assembly behaviours were controlled by the competition between the surfactant interaction and the magnetic dipole interaction. The catalytic performance of these Pd–Ni assemblies is strongly dependent on their compositions.

Posted on 23 July 2014 | 8:10 am

Synthesis and Molecular Structures of Monosubstituted Pentamethylcobaltocenium Cations

(Amino-?5-cyclopentadienyl)(pentamethyl-?5-cyclopentadienyl)cobalt(III) hexafluorophosphate (6PF6) was prepared by a route that started with the synthesis of the zwitterion (oxycarbonyl-?5-cyclopentadienyl)(pentamethyl-?5-cyclopentadienyl)cobalt(III) (1). The acidification of 1 created the carboxylic acid 2PF6, which was converted into the acyl chloride 3PF6. The reaction with NaN3 afforded the azide 4PF6, which was transformed to the carbamate 5PF6. The hydrolysis of 5PF6 afforded the desired aminocobaltocenium compound 6PF6. The oxidation of 6PF6 yielded the (nitro-?5-cyclopentadienyl)(pentamethyl-?5-cyclopentadienyl)cobalt(III) cation 7+. For 1, 2+, 4PF6, 6PF6, and 7PF6, X-ray structure analyses were performed. The electronic structure of 6+ calculated by DFT methods revealed a short C–N bond, which is in agreement with the molecular structure obtained from X-ray structure analysis. The pKa value of 6PF6 was estimated from aqueous solution. Cyclic voltammetry studies show a reversible one-electron reduction and an irreversible one-electron oxidation. From the zwitterion 1, the aminocobaltocenium cation 6+ can be synthesized in five steps. The target compound 6+ demonstrates an electronic structure between that of an amine and that of an iminium cation. It reacts as a weak acid in aqueous solution and can be oxidized to the corresponding nitrocobaltocenium cation 7+ like primary amines.

Posted on 22 July 2014 | 12:10 pm

Photoinduced Topological Transformation in Mesoscopic Inorganic Nanoparticles: Application as a UV Sensor

Achieving topological transformation in an inorganic chemical system is an ongoing challenge. We show that such a topological transformation can be achieved in a simple metal-oxide based inorganic system of soft-oxometalates (SOMs). Starting from a dispersion of heptamolybdate-based SOM nanotubes, molybdenum blue SOM nanospheres were synthesised by application of UV-irradiation. This transformation is accompanied by a colour change of the system from colourless to blue. The starting material and product were characterised based on an array of techniques including scanning electron microscopy, dynamic light scattering, horizontal attenuated total reflectance infrared spectroscopy, and UV/Vis spectroscopy. The possibility of using this system as a UV detector is also discussed. Irradiation of ammonium heptamolybdate tetrahydrate soft-oxometalate (SOM) nanorods with UV light leads to their topological transformation into molybdenum blue SOM nanospheres. This transformation is accompanied by a colour change from colourless to blue, which can be exploited for UV sensing. Thus, when a particular threshold amount of UV irradiation is absorbed, the nanorods change colour.

Posted on 22 July 2014 | 12:10 pm

Mixed-Donor Amido–Siloxo Actinide(IV) Halide and Alkyl Complexes with an Aryl Cipso Interaction

The synthesis and characterisation of a series of new actinide(IV) complexes supported by the mixed-donor amido–amino–siloxo framework [RN(Li)SiMe2N(R)SiMe2OLi] ([RNNO]Li2; R = 2,4,6-Me3Ph, 2,6-iPr2Ph) are presented. The reaction of 1 equiv. of [RNNO]Li2 with ThCl4·2DME (DME = 1,2-dimethoxyethane) in DME generated {Li·nDME}{[RNNO]2Th2Cl5} (1: R = 2,4,6-Me3Ph, n = 2; 2: R = 2,6-iPr2Ph, n = 3) in high yield, and the addition of [?Me?3PhNNO]Li2 to UCl4 in tetrahydrofuran (THF) resulted in the formation of {[?Me?3PhNNO]UCl3Li·THF}2 (3). The structures of 1–3 indicate that they retain LiCl as “ate” complexes. The addition of 2 equiv. of [?Me?3PhNNO]Li2 to ThCl4·2DME and UCl4 gives the bis-ligated complexes [?Me?3PhNNO]2ThClLi (4) and [?Me?3PhNNO]2U (5), respectively. In 1–5, the [RNNO]2– ligands all coordinate through the amido and siloxo donors as well as the ipso carbon atom of the phenyl group of the amido ligand but not through the central amino group. Complex 3 can be alkylated through the addition of 2 equiv. of LiCH2SiMe3 to give [?Me?3PhNNO]U(CH2SiMe3)2 (6) or NaCp (Cp = cyclopentadienyl) to give [?Me?3PhNNO]UCp2 (7); the latter has been structurally characterised. A new series of mixed-donor amido–siloxo actinide(IV) halide and alkyl complexes feature an aryl Cipso interaction of the amido aryl group with the metal centre.

Posted on 22 July 2014 | 12:10 pm

Transistor Application of Phenacene Molecules and Their Characteristics

The characteristics of field-effect transistors (FETs) fabricated from thin films and single crystals of phenacene molecules are fully reported in this review together with the electronic and crystal structures of phenacenes. Phenacene molecules possess a low HOMO level and a wide band gap. The highest mobility observed in the phenacene thin-film FETs is 7.4 cm2?V–1?s–1 for [6]phenacene, and in single-crystal FETs the highest value is 6.3 cm2?V–1?s–1 for [7]phenacene. The phenacene thin-film FETs show O2-sensing properties unlike their single-crystal FETs. The bias-stress effect is fully investigated for phenacene single-crystal FETs. Furthermore, the low-voltage operation of phenacene single-crystal FETs with electric-double-layer (EDL) capacitors is reported. The temperature dependence of phenacene single-crystal FETs is reported to clarify the transport mechanism, which is suggestive of band-like transport. Field-effect transistors (FETs) can be fabricated with thin films and single crystals of phenacene. The excellent p-channel FET characteristics that have been found by our group are fully reported in this review.

Posted on 22 July 2014 | 12:10 pm

Kinetics and Mechanism of the Reaction of Hydrogen Sulfide with Diaquacobinamide in Aqueous Solution

We conducted a detailed kinetic study of the reaction of the vitamin B12 analog diaquacobinamide [(H2O)2Cbi(III)] with hydrogen sulfide in water from pH 3 to 11. The reaction proceeds in three steps: (1) the formation of three different complexes between cobinamide and hydrogen sulfide, viz., (HO–)(HS–)Cbi(III), (H2O)(HS–)Cbi(III), and (HS–)2Cbi(III); (2) inner-sphere electron transfer (ISET) in the two complexes with one coordinated HS– ligand to form the reduced cobinamide complex [(H)S]Cbi(II); and (3) the addition of a second molecule of hydrogen sulfide to the reduced cobinamide. ISET does not proceed in the (HS–)2Cbi(III) complex. The final products of the reaction between cobinamide and hydrogen sulfide were found to be independent of pH, and the main product is a complex of cobinamide(II) with the anion radical SSH2–. The reduction of diaquacobinamide [(H2O)2Cbi(III)] by hydrogen sulfide proceeds through inner-sphere electron transfer (ISET) in the two complexes with one coordinated HS– ligand, viz., (HO–)(HS–)Cbi(III) and (H2O)(HS–)Cbi(III), to form the reduced cobinamide complex [(H)S]Cbi(II). ISET does not proceed in the (HS–)2Cbi(III) complex.

Posted on 21 July 2014 | 1:10 pm

Aerial CO2 Trapped as CO32– Ions in a Dimeric Capsule That Efficiently Extracts Chromate, Sulfate, and Thiosulfate from Water by Anion-Exchange Metathesis

The tris(2-aminoethyl)amine-based (tren-based) 3-cyanophenyl-substituted tripodal urea L1, one of the familiar urea-based anion receptors, has shown encapsulation of CO32– ions as the carbonate capsule [(L1)2·(CO3)·(TBA)2] (1, TBA = tetrabutylammonium) by the fixation of aerial carbon dioxide from basic dimethyl sulfoxide (DMSO) solution. Single-crystal X-ray structural analysis confirmed the encapsulation of CO32– ions in the cavity of a dimeric capsular assembly of L1 (9.62 Å) through the formation of twelve strong N–H···O hydrogen-bonding interactions. The excellent CHCl3 and CH2Cl2 solubility of 1 has been exploited for the liquid–liquid (L–L) extraction of CrO42–, SO42–, and S2O32– ions from water by anion-exchange metathesis. The extraction of these anions from water was unambiguously confirmed by 1H NMR spectroscopy, IR spectroscopy, powder XRD (PXRD), and single-crystal X-ray diffraction analysis. The 1H NMR spectroscopic analysis of the bulk extracts supports the formation of 2:1 (host–guest) complexes. For the CrO42– ion, the 53Cr NMR spectrum of the bulk extract shows a characteristic peak at ? = –99.98 ppm. The complexes of CrO42–, S2O32–, and SO42– ions with L1 (i.e., 2–4, respectively) were obtained from crystallization of the bulk extracts and show anion-assisted dimeric capsular assemblies of L1 through multiple N–H···X (X = O, S) interactions. The dimensions of the anion-encapsulated capsular assemblies are quite similar to that of the carbonate capsule and are 9.70 Å for [(L1)2·(CrO4)·(TBA)2] (2), 9.61 Å for [(L1)2·(S2O3)·(TBA)2] (3), and 9.71 Å for [(L1)2·(SO4)·(TBA)2] (4). Quantification by weighing the bulk extract shows that 1 can separately extract ca. 90?% of the above three anions from water by anion-exchange metathesis. The quantitative estimations of the extractions of SO42– and CrO42– ions were further verified by gravimetric analysis by BaSO4 and BaCrO4 precipitation techniques, respectively. The extraction of SO42– ions from water was also demonstrated under alkaline conditions (pH 12.5) and in the presence of an excess of nitrate ions. Further, the quantification of CrO42– extraction was established by solution-state UV/Vis studies. In the solid state, a tripodal urea receptor encapsulates CO32– ions in its dimeric capsular assembly, which is further exploited for the liquid–liquid (L–L) extraction of CrO42–, S2O32–, and SO42– ions from water. Different spectroscopic techniques and X-ray diffraction studies confirm the efficient extraction of these environmentally relevant anions.

Posted on 21 July 2014 | 1:10 pm

Tetranuclear [2×2] Square-Grid Lanthanide(III) Complexes: Syntheses, Structures, and Magnetic Properties

The reactions of lanthanide(III) nitrate salts (DyIII, TbIII, GdIII, and ErIII) with the aroylhydrazone-based multidentate ligand 6-(hydroxymethyl)-N?-[1-(pyridin-2-yl)ethylidene]picolinohydrazide (LH2) in the presence of Et3N in a molar ratio of 1:1:4 afforded a series of homometallic tetranuclear lanthanide(III) complexes, [Ln4(LH)4(?2-OH)3(?2-OMe)]4NO3·xMeOH·yH2O (1, Ln = Dy, x = 2, y = 4; 2, Ln = Tb, x = 2, y = 4; 3, Ln = Gd, x = 2, y = 5; and 4, Ln = Er, x = 3, y = 3). X-ray diffraction studies revealed that all of the complexes contain a tetracationic [2×2] square-grid-like [Ln4(?2-OH)3(?2-OMe)(?2-O)4]4+ core, which is assembled by the concerted coordination action of four monoanionic [LH]– ligands along with three ?2-OH ligands and a ?2-OMe ligand. All of the lanthanide centers are eight-coordinate and adopt distorted triangular-dodecahedral coordination geometries with two different types of coordination environments (6O,2N and 4O,4N). The magnetic susceptibility measurements of the complexes reveal both the presence of all-antiferromagnetic coupling interactions as well as both isotropic (3) and anisotropic (1, 2, 4) single-ion contributions, which do not result in slow relaxation characteristics typical of single-molecule magnets. The reactions of a multicompartmental ligand with rare-earth(III) nitrate salts afford a series of homometallic Ln4 complexes [Ln = Dy, Tb, Gd, and Er] with [2×2] square-grid topology. Magnetic studies reveal the presence of all-antiferromagnetic exchange interactions and ligand-field-induced effects for the Dy, Tb, and Er complexes, whereas an isotropic model suffices for the Gd complex.

Posted on 21 July 2014 | 1:10 pm

Polynuclear Copper(II) Complexes as Catalysts for the Peroxidative Oxidation of Cyclohexane in a Room-Temperature Ionic Liquid

The reaction of copper(II) nitrate hydrate with sodium 2-[2-(2,4-dioxopentan-3-ylidene)hydrazinyl]terephthalate (Na2HL1) in the absence or presence of imidazole (im) leads to the new complexes [(H2O)Cu0.5{(?-L1-1?O:2?3N,O?,O?)Cu(H2O)2}]2 (1) and [Cu(im)(?-HL1-1?O:2?3N,O,O?)]2 (2), respectively, whereas the 1D coordination polymer [Cu2(H2O)2(?-H2L2-1?3N,O,O?:2?O?)(?-L2-1?3N,O,O?:2?2N?,O?)]n (3) is obtained from Cu(NO3)2·2.5H2O and sodium 2-[2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl]terephthalate (Na2HL2). All of the compounds were characterized by ESI-MS, IR spectroscopy, elemental analysis and X-ray diffraction analysis. Di- or tri-deprotonated ligands display different coordination modes and lead to distinct nuclearities of the CuII complexes depending on the conditions used for the syntheses. Complexes 1–3 were successfully tested as dual-role catalysts for cyclohexane oxidation under acid-free conditions in the ionic liquid [1-butyl-3-methylimidazolium tetrafluoroborate, (bmim)(BF4)] as well as in acetonitrile. The application of the ionic liquid (IL) increased the product yield and turnover number and decreased the reaction time, in comparison with those for the use of the conventional acetonitrile solvent. Easy recycling of the catalyst, with preservation of almost the initial activity and selectivity, was also achieved by using the IL medium. Multinuclear CuII complexes with a catalytic metal centre and an acid functionality catalyze the peroxidative oxidation of cyclohexane in acid-free water/air/CH3CN or ionic liquid media.

Posted on 21 July 2014 | 1:10 pm

Hydrophilic Pd0 Complexes Based on Sugars for Efficient Suzuki–Miyaura Coupling in Aqueous Systems

Two classes of hydrophilic Pd0 complexes containing P,N and N,N sugar-based ligands were prepared and tested in the Suzuki–Miyaura cross-coupling reaction under environmentally friendly aqueous conditions. The best catalyst was tolerant towards different substrates, and its activity is comparable with the highest values reported so far for reactions in aqueous media [loading 0.0010?%, turnover frequency (TOF) 3.5?×?104 h–1]. Sugar-derived hydrophilic Pd0 complexes are prepared and tested in aqueous Suzuki–Miyaura cross-coupling reactions. These conditions allow the green and sustainable synthesis of biaryls. The best catalysts achieve very good performances [turnover frequencies (TOFs) up to 3.5?×?104 h–1; catalyst loadings down to 0.0010 mol-%], among the best reported for this reaction in aqueous conditions.

Posted on 21 July 2014 | 1:10 pm

High-Yielding Synthesis of a Hetero-Pacman Compound and the Characterization of Intermediates and Side-Products

Through an optimized synthetic procedure, metalloligand 5, which features a hetero-Pacman scaffold comprising a porphyrin and a terpyridine moiety, has been assembled by a double Suzuki reaction. In a subsequent step, a ruthenium-bipyridine fragment was introduced at the terpyridine coordination site of metalloligand 5 to form complex 6, which was fully characterized and its potential application in water oxidation catalysis tested. A number of side-products were isolated and characterized during the two-step synthesis procedure, including a hydroxylated version of the boronic acid substituted precursor molecule derived by a base-assisted rearrangement. The compounds described herein extend the Pacman concept to the assembly of different metal combinations with different coordination spheres and their interactions in the activation of small molecules. A new high-yielding synthesis towards xanthene-porphyrin precursors is presented. These building blocks can be used for the formation of a multitude of different heterodinuclear complexes with the Pacman architecture. A hetero-Pacman scaffold featuring a porphyrin and a ruthenium polypyridine complex fragment that shows intriguing structural and spectroscopic properties was produced herein by a double Suzuki reaction.

Posted on 21 July 2014 | 1:10 pm

Synthesis, Properties, and Applications of Light-Insensitive Silver(I) Cyanoximates

The reaction between AgNO3 and ML [M = K+, Na+; L = anion of the deprotonated cyanoxime – 39 of these anions are known, but only twelve form light-stable silver(I) complexes] at room temperature in aqueous solutions leads to sparingly soluble, colored AgL in high yield. All twelve of the known Ag complexes were characterized by using a variety of spectroscopic methods and single-crystal X-ray analysis, which revealed the formation of coordination polymers of various complexities. The silver(I) compounds demonstrate a very significant (for multiple years!) stability towards visible light. There are three areas of potential practical applications of these unusual complexes: (1) detectors of UV radiation that do not require electric feed, (2) non-electrical indicators for gases of industrial importance, (3) antimicrobial additives to light-curable acrylate polymeric glues, fillers, and adhesives used during the introduction of indwelling medical devices. The chemical, structural, technological, and biological aspects of the application of coordination polymers based on AgI cyanoximates are reviewed. Twelve coordination polymers of silver(I) cyanoximates of composition AgL were found to be very stable towards visible light. Three areas of potential practical relevance of these unusual complexes have emerged. The chemical, structural, technological, and biological aspects of the applications of these compounds are reviewed.

Posted on 18 July 2014 | 3:10 pm

Polynuclear Heterometallic Complexes from Metal Powders: The “Direct Synthesis” Approach

The synthesis of polynuclear coordination compounds, particularly heterometallic coordination compounds, remains a challenge for modern chemistry. Spontaneous self-assembly (SSA) is a primary approach that proceeds by broad screening, typically with simple, flexible ligands and available metal salts. The “direct synthesis” is a class of SSA, but prescribes the use of zero-valent metal(s) as a starting material, typically oxidized by air oxygen, which results in a deficiency of anions in the reaction mixture and forces deprotonation of the protic ligand(s) with the formation of unexpected products. The “direct synthesis” approach has been successfully applied to the preparation of heterometallic complexes, which has allowed the isolation of numerous complexes, many with uncommon structures. In this review we summarize our experience in the field of the “direct synthesis” of polynuclear heterometallic complexes, covering preparative and structural aspects as well as applications of the compounds obtained. In this review we summarize our experience in the field of the “direct synthesis” of polynuclear heterometallic complexes, covering preparative and structural aspects as well as applications of the compounds obtained.

Posted on 18 July 2014 | 9:40 am

Vanadium Complexes as Prospective Therapeutics: Structural Characterization of a VIV Lysozyme Adduct (Eur. J. Inorg. Chem. 21/2014)

The cover picture shows a representation of the HEWL–VIVO(pic)2 adduct (HEWL: hen egg white lysozyme). Our X-ray crystallography results show that the VIVO(pic)2 complex covalently binds to the COO– group of the side-chain Asp52 residue of HEWL. Although a relatively long VIV=O bond was obtained (ca. 1.82 Å), a combined approach using EPR and DFT techniques confirms that the carboxylate group of the Asp52 residue of HEWL binds to VIVO(pic)2 and, moreover, that the oxidation state of vanadium is VIV. We conclude that the long VIV=O bond obtained is the result of the exposure of the crystals to the very intense X-ray beam, which induces a progressive reduction of VIV to VIII and the concomitant bond elongation. These results may be important for the development of vanadium complexes as therapeutic agents, namely as oral insulin substitutes for the treatment of diabetes. We would like to thank Rui Pedro Bordalo for designing the cover picture. Details are discussed in the Short Communication by J. C. Pessoa, T. Santos-Silva et al. on p. 3293 ff. For more on the story behind the cover research, see the Cover Profile.

Posted on 18 July 2014 | 9:26 am

Vanadium Complexes as Prospective Therapeutics: Structural Characterization of a VIV Lysozyme Adduct

Invited for the cover of this issue is the group of Teresa Santos-Silva from Universidade Nova de Lisboa and João da Costa Pessoa, Universidade de Lisboa, Portugal. The cover image shows a representation of the HEWL–VIVO(pic)2 adduct (HEWL: hen egg white lysozyme; pic: picolinato). It is essential to understand how vanadium compounds are transported in blood, as this determines their bioavailability and pharmacokinetics...Read more about the story behind the cover in the Cover Profile and about the research itself on p. 3293 ff.

Posted on 18 July 2014 | 9:26 am

Masthead: Eur. J. Inorg. Chem. 21/2014

Posted on 18 July 2014 | 9:26 am

Masthead: Eur. J. Inorg. Chem. 21/2014

Posted on 18 July 2014 | 9:25 am

Graphical Abstract: Eur. J. Inorg. Chem. 21/2014

Posted on 18 July 2014 | 9:25 am

Solid-State NMR Characterization of Paramagnetic Bis(L-valinato)copper(II) Stereoisomers – Effect of Conformational Disorder and Molecular Mobility on 13C and 2H Fast Magic-Angle Spinning Spectra

The solid-state 13C and 2H NMR spectra of paramagnetic anhydrous trans-bis(L-valinato)copper(II) and cis-aquabis(L-valinato)copper(II) complexes have been obtained. Under the very fast MAS conditions, both the 13C and 2H MAS spectra were well enough resolved to allow the easy distinction between the trans and cis stereoisomers. The conformational disorder observed previously in the X-ray structure of the cis isomer was also reflected in the 13C and 2H MAS spectra. Variable-temperature 2H MAS spectra of differently deuterated ligand species, that is, the copper(II) complexes with L-[D2]valine, L-[D8]valine, and L-[D10]valine, suggested the dynamic nature of this disorder in the aqua cis isomer and confirmed static ND2 deuterons in the anhydrous trans isomer. Quantum chemical DFT/B3LYP calculations of the 13C hyperfine (Fermi contact) shifts of the paramagnetic term were useful as assignment aids in the interpretation of the 13C MAS spectra. The 13C and 2H fast magic-angle spinning (MAS) NMR spectra of paramagnetic bis(L-valinato)copper(II) complexes enable the distinction of trans and cis stereoisomers in the solid state. The study of deuterated bis(L-valinato)copper(II) complexes demonstrates the wealth of information available from the 2H MAS spectra of paramagnetic compounds, such as dynamic conformational changes inside the crystal lattice.

Posted on 27 June 2014 | 11:10 am

Aqueous Crystallization Strategy for Metastable h-MoO3 Crystals with Polyvinylpyrrolidone Induction

Micro-sized hexagonal-phase MoO3 (h-MoO3) crystals were successfully prepared by a polyvinylpyrrolidone (PVP) induced aqueous route with (NH4)6Mo7O24·4H2O and HCl as raw materials. The linear structure of the PVP molecules matches the tunnel structure of the metastable h-MoO3 crystals and, thus, enables the induced crystallization in an aqueous solution even at near-ambient temperatures (40–50 °C). The achieved h-MoO3 crystals have good monodispersity with a one-dimensional (1D) outline and hexagonal cross-section. The H+/Mo ratio is another key factor for the synthesis of h-MoO3 crystals. The photochromic properties of PVP-dependent samples of h-MoO3 crystals were studied under natural sunlight irradiation. Hexagonal MoO3 (h-MoO3) crystals are successfully prepared from (NH4)6Mo7O24·4H2O and HCl by a polyvinylpyrrolidone (PVP) induced aqueous route. The linear PVP molecules match the tunnel structure of metastable h-MoO3 crystals and enable crystallization in an aqueous solution at near-ambient temperatures. The photochromic properties of PVP-dependent samples of h-MoO3 crystals are studied.

Posted on 24 June 2014 | 5:11 pm

A Trinuclear Zinc–Schiff Base Complex: Biocatalytic Activity and Cytotoxicity

A novel trinuclear zinc(II) complex [Zn3L2(?-O2CCH3)2(CH3OH)4] (1) that contains an N,O-donor Schiff base ligand {H2L = 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol} has been synthesized and crystallographically characterized. The X-ray crystal structure of 1 contains three zinc(II) centers, which have distorted-octahedral coordination geometry, and the molecule crystallizes in the Pbcn space group. The zinc(II) complex displays significant catecholase oxidation activity in methanolic medium through a ligand-centered radical pathway. This is the first example of catecholase oxidation through a trinuclear zinc(II)–Schiff base complex by means of the formation of a mononuclear intermediate as [ZnL(dtbc)] (dtbc = 3,5-di-tert-butylcatechol). The fluorescence property of 1 indicates that it can serve as a potential photoactive material. It effectively cleaves the double strand of pBR 322 plasmid DNA at a given concentration (25 ?M). The complex shows remarkable cytotoxicity against a human hepatocarcinoma cell line (HepG2). A crystallographically characterized trinuclear zinc(II) complex [Zn3L2(?-O2CCH3)2(CH3OH)4] (1) that contains an N,O-donor Schiff base ligand {H2L = 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol} exhibits potential ligand-centered catalytic activity relevant to catechol oxidase. The molecule shows remarkable cytotoxicity against a human hepatocarcinoma cell line (HepG2).

Posted on 24 June 2014 | 5:11 pm

Vanadium Sandwich Complexes with Boroxine and Boronyl Boroxine Ligands

A DFT investigation on half-sandwich-type C3v B3O3X3V, full-sandwich-type D3d [B3O3X3]2V, and triple-decker complexes [B3O3X3]3V2 (X = H, BO) containing B3O3H3 or B3O3(BO)3 ligands were performed. Both B3O3H3 and B3O3(BO)3 units serve as robust inorganic ligands in B3O3X3V, [B3O3X3]2V, and [B3O3X3]3V2 complex series. Effective d–? coordination interactions between the partially filled 3d orbitals of the transition-metal center and the delocalized ? orbitals of the B3O3X3 ligands maintain the stabilities of the complexes. The largest contributions to the orbital interactions in the B3O3X3V, [B3O3X3]2V, and [B3O3X3]3V2 complexes come from the V??B3O3X3 ? back donation. The thermodynamic stabilities and magnetic properties of these complexes were also investigated. These magnetic complexes were found to be particularly stable with respect to their reaction energy. The sandwich structural pattern developed in this work expands the structural domain of transition-metal complexes by introducing inorganic B3O3H3 and B3O3(BO)3 into traditional sandwich-type structures, and this pattern may be extended to [B3O3X3]nVn–1 sandwiches (n ? 4), which could act as linear magnetic wires. The C3v B3O3X3V, D3d [B3O3X3]2V, and [B3O3X3]3V2 (X = H, BO) are favored in energy and could be targeted in future experiments. The sandwich structural pattern developed in this work expands the structural domain of transition-metal complexes by introducing inorganic B3O3H3 and B3O3(BO)3 into traditional sandwich-type structures and may be extended to [B3O3X3]nVn–1 (n ? 4), which could act as linear magnetic wires.

Posted on 24 June 2014 | 12:20 pm

Structural and Electrochemical Studies of Copper(I) Complexes with Diethoxyphosphoryl-1,10-phenanthrolines

Two series of copper(I) complexes with diethoxyphosphoryl-substituted 1,10-phenanthroline ligands were synthesized and characterized in the solid state and in solution. The first comprised mixed-ligand CuI complexes with phenanthroline and triphenylphosphine. The second series includes bis-chelates with two phenanthroline ligands. According to the X-ray data for the six complexes, the ditopic phenanthroline ligands exhibit bidentate coordination to the copper(I) atom through two nitrogen atoms in both series. Solution equilibria involving different phenanthroline copper(I) species were studied by 1H and 31P NMR spectroscopy, electrochemistry, and spectroelectrochemistry. The solution speciation of these labile complexes is different for these two series and depends on the nature of solvent and the location of the phosphorus substituent on the phenanthroline backbone. Coordinating solvents can replace a bromide, triphenylphosphine, and even a phenanthroline ligand in the inner coordination sphere of the metal center. Copper(I) complexes with ?-substituted phenanthrolines easily dissociate even in noncoordinating solvents such as CH2Cl2 and CHCl3. Ligand-exchange reactions leading to less sterically hindered species were observed under the utilized solution conditions. The coordination mode of the phenanthroline chelators does not change under any of the utilized solution conditions, and binding of the phosphoryl group to the metal center was never observed by spectroscopic or spectroelectrochemical methods. Copper(I) complexes with diethoxyphosphoryl-substituted 1,10-phenanthroline ligands are synthesized and characterized in the solid state and in solution by X-ray diffraction, 1H and 31P NMR spectroscopy, electrochemistry, and spectroelectrochemistry.

Posted on 24 June 2014 | 12:10 pm

Hydrothermal Fabrication and Luminescence Properties of One-Dimensional TiO2:Eu3+ Spindlelike Nanorods

Highly crystalline and uniform TiO2:Eu3+ spindlelike nanorods have been successfully synthesized through a facile hydrothermal route with citric acid (H3Cit) and ethanediamine (en) as the assistant agents for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and photoluminescence (PL) spectroscopy were utilized to characterize the samples. In the synthetic process, the dosages of ethanediamine and citric acid are important parameters that affect the morphology and size of the final products. A possible formation process of the samples has been proposed in detail. The existence of Eu3+ sites in the TiO2 nanorods was proved by site-selective spectroscopy. Furthermore, the TiO2:Eu3+ spindlelike nanorods exhibit bright red (Eu3+, 5D07F2) luminescence under ultraviolet (UV) excitation; therefore, they may find potential applications in fluorescent lamps and field-emission displays (FEDs). A hydrothermal method is used to synthesize uniform TiO2:Eu3+ spindlelike nanorods for the first time. In the presence of citrate (Cit3–) ions and ethanediamine (en) molecules, the nanocrystals aggregate gradually through assembly and finally form well-defined TiO2:Eu3+ spindlelike nanorods.

Posted on 24 June 2014 | 12:10 pm

CaMg2P6O3N10 – A Quinary Oxonitridophosphate with an Unprecedented Tetrahedra Network Structure Type

CaMg2P6O3N10 has been synthesized starting from stoichiometric amounts of Ca(N3)2, Mg3N2, P3N5, and PON in a high-pressure/high-temperature reaction at 8 GPa and 1100 °C. Adding small amounts of NH4Cl to the starting mixture afforded single crystals of CaMg2P6O3N10, which form transparent, colorless truncated octahedra. The crystal structure [space group I41/acd (no. 142), a = 12.494(1), c = 23.797(2) Å, Z = 16] was solved and refined by single-crystal X-ray diffraction analysis and confirmed by electron diffraction and transmission electron microscopy, including HRTEM image simulations. Rietveld refinement proved the phase purity of the product. FTIR analysis confirmed the absence N–H groups in the structure. Bond valence and lattice energy calculations (MAPLE) of the title compound are discussed. The crystal structure consists of polyhedral building units constructed from vertex-sharing P(O,N)4 tetrahedra with condensed dreier and sechser rings. CaMg2P6O3N10 has been synthesized by a high-pressure/high-temperature reaction at 8 GPa and 1100 °C and investigated by single-crystal X-ray diffraction. The structure was confirmed by TEM investigations, including SAED and HRTEM image simulations. It represents a novel oxonitridophosphate with an unprecedented network of tetrahedra.

Posted on 23 June 2014 | 2:40 pm

Layer-by-Layer Deposition of Highly Transparent Multifunctional Gd2O3:RE/SiO2 (RE = Eu and Tb) Films

Transparent, luminescent (Gd2O3:RE/SiO2) thin films (RE = Eu and Tb) have been fabricated by annealing [RE-doped layered gadolinium hydroxide (LGdH:RE) nanosheet/SiO2 nanoparticle]n films (n = the number of deposition cycles) deposited on a single quartz glass substrate by the layer-by-layer (LbL) assembly technique. To avoid energy transfer between different activator ions, which frequently occurs when multiple activator-doped LGdHs are used as precursor nanosheets, the emission colors of our oxide films were tuned by changing the mixing ratios of the individual LGdH:Eu and LGdH:Tb colloidal solutions used in the LbL deposition. Deposited films of sufficient thickness (n = 30) displayed bright emission colors ranging from green to red under 254 nm UV irradiation, depending on the mixing ratio. Although the large number of deposition cycles resulted in a lack of antireflection properties in the films, the porous surfaces induced by SiO2 nanoparticles led to superhydrophilic and antifogging properties without significant loss of transparency in the visible range compared with the bare quartz substrate. Transparent multifunctional phosphor films with multicolor tunability and superhydrophilic/antifogging properties have been fabricated by layer-by-layer assembly of RE-doped layered gadolinium hydroxide (LGdH:RE; RE = Eu and Tb) nanosheets and SiO2 nanoparticles on a quartz substrate.

Posted on 18 June 2014 | 1:11 pm

Self-Organization of Anderson-Based Amphiphiles

Amphiphilic molecules with polyoxometalate head groups have attracted much attention in the last decade. In this paper, we report the successful synthesis and full characterization of three new Anderson-based amphiphiles, 3a, 3b, and 3c, which were formed by covalently attaching different numbers of hydrophobic alkyl chains onto both sides of Anderson clusters. The self-organization process has been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy and dynamic light scattering (DLS) in a series of acetonitrile/water mixtures. The experimental results have shown intriguing morphologies along with the change of solvent polarity and structural conformation, which provides us with a better understanding of the mechanism of self-organization and the relationship between the self-organization morphology and the molecular structures. New polyoxometalate-based amphiphiles with Anderson cluster head groups are synthesized by covalently tethering alkyl chains onto the Anderson cluster. In CH3CN/H2O mixtures, these amphiphiles show intriguing morphologies that can be finely tuned. The structural conformation, hydrophobic–hydrophobic interactions, and solvent polarity profoundly influence the self-organization of these amphiphiles.

Posted on 17 June 2014 | 8:20 pm

Facile in situ Syntheses of Highly Water-Stable Acidic Sulfonated Mesoporous Silica without Surfactant or Template

A new simple method to prepare acidic mesoporous sulfonated silica in situ without any surfactant is reported. The prepared catalysts were characterized by XRD, nitrogen adsorption, thermogravimetric analysis (TGA), and elemental analysis. The concentration of –SO3H groups was measured by titration, and FTIR was applied to confirm the successful incorporation of the strong acid sites. The in situ sulfonated silica (ISS) has a large surface area with a narrow range of mesoporosity and good thermal stability. Moreover, the preparation method has the advantage of easy control of the acid concentration and versatile synthesis. The ISS was used in catalytic hydrolysis and showed remarkable reusability even under very harsh conditions. The butylation of phenol was conducted over ISS to utilize the mesoporosity of the catalysts. Finally, the ISS catalysts might be used in various acid catalyses owing to the advantages of their simple/inexpensive preparation, reusability, and mesoporosity. New facile syntheses of acidic mesoporous catalysts and their catalytic applications are reported. The catalysts are extremely stable in water and at high temperature and can be used many times even under very harsh conditions

Posted on 17 June 2014 | 8:20 pm

A Single-Phase Emission-Tunable Ca5(PO4)3F:Eu2+,Mn2+ Phosphor with Efficient Energy Transfer for White LEDs

Eu2+/Mn2+-co-doped white-emitting Ca5(PO4)3F phosphors have been synthesized by a combustion-assisted synthesis method. The PXRD patterns confirmed the single-phase fluorapatite crystal structure for all the samples independently of their substitution level. Their luminescence properties reveal that the developed phosphors can efficiently convert UV light in a broad range from 250 to 420 nm into tunable white emission. Based on the luminescence spectra and fluorescence decay curves, we can confirm that energy transfer from the Eu2+ to Mn2+ ions takes place in the Ca5(PO4)3F:Eu2+,Mn2+ phosphors, and that the energy-transfer efficiency increases with increasing Mn2+ content. The emission colors of the obtained phosphors can be tuned from blue to white and eventually to yellow by controlling the doping content of the Eu2+ and Mn2+ ions. These results suggest that these phosphors are potential single-component white-light phosphors for n-UV-pumped white LEDs. Ca5(PO4)3F:Eu2+,Mn2+ phosphors with blue and orange double emission bands have been synthesized. Energy transfer between Eu2+ and Mn2+ was discovered and the transfer efficiencies estimated. The hues of the phosphors could be changed from blue to white and then to yellow by varying the relative concentrations of Eu2+ and Mn2+.

Posted on 17 June 2014 | 8:20 pm

Six-Membered Silacycle Odorants: Synthesis and Olfactory Characterization of Si Analogues of Artemone, ?-Dynascone, and Herbac

Si-Artemone (4a), Si-?-Dynascone (5a), and Si-Herbac 6a, which are Si analogues of the commercial fragrance ingredients Artemone (1), ?-Dynascone (2), and Herbac (3), were synthesized expediently by the insertion of terminal alkynes into silacyclobutane 7a. The sensory characterization results revealed that 4a and 6a had quite similar odor qualities compared with those of 1 and 3, whereas 5a had a totally different odor character relative to that of 2. In terms of the odor threshold values, that of 4a was slightly more substantive than that of its carbon analogue 1, 6a was less potent than its carbon analogue 3, whereas that of 5a was approximately one-sixth that of its carbon analogue 2. The combination of the sila-substitution concept with the insertion reactions of terminal alkynes into silacyclobutane efficiently led to the sila-odorants Si-Artemone, Si-?-Dynascone, and Si-Herbac. Si-Artemone and Si-Herbac have sensory characters similar to those of their unsubstituted analogues, whereas Si-?-Dynascone has an odor quite different to that of its unsubstituted analogue.

Posted on 17 June 2014 | 8:10 pm

Heterometallic Pentanuclear [Ni4Ln] (LnIII = Gd, Tb, Dy, Ho) Complexes: Accidental Orthogonality Leading to Ferromagnetic Interactions

The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol (LH2) with NiII and LnIII salts afforded a series of heterometallic pentanuclear compounds [Ni4Ln(L)4(OAc)2(MeOH)4](NO3)(MeOH) [LnIII = Gd (1), Dy (2), Tb (3), Ho (4)]. Four dianionic L2– ligands and two acetate anions hold together four NiII and one LnIII ion to form a Ni4Ln core possessing a distorted tetrahedral geometry. All the NiII ions are hexacoordinate (6 O) with a distorted octahedral geometry whereas the LnIII ion is octacoordinate (8 O) with a distorted square-antiprism geometry. All the NiII ions are connected to the central LnIII ion through ?2 bridging of one deprotonated phenolic oxygen and two deprotonated alkoxy oxygen atoms. The magnetic properties of 1–4 were investigated in the temperature range 2–300 K. The magnetic properties of 1 were fitted by using a Hamiltonian containing isotropic exchange, NiII local zero-field-splitting, and Zeeman effects (? = ?exchange + ?zfs + ?zeeman). The molecular structures of 1–4 reveal that the Ni–O–Ln angle is around 89° whereas the Ni–O–Ni angle is about 96°. Because of this accidental orthogonality, ferromagnetic interactions between the nearest-neighbor NiII ions and between NiII and LnIII ions have been observed. The observed J values are 0.34 and 1.88 cm–1 between GdIII–NiII and NiII–NiII, respectively. The reaction of 6-formyl-2-(hydroxymethyl)-4-methylphenol with appropriate lanthanide salts followed by reaction with Ni(OAc)2·4H2O affords pentanuclear heterobimetallic compounds containing a [Ni4Ln] core. These complexes have a distorted tetragonal core structure in which the M–O–M? (M? = NiII/LnIII) angles are around 90°.

Posted on 16 June 2014 | 1:40 pm

Synthesis and Characterization of Spirosilanes – 1,2-Hydroboration and 1,1-Carboboration

Starting from dichloro(divinyl)silane, the dialkynyl(divinyl)silanes (CH2=CH)2Si(C?CR)2 (R = tBu, p-tolyl, 3-thienyl, CH2NMe2) were prepared. These silanes were treated with 9-borabicyclo[3.3.1]nonane (9-BBN) for 1,2-hydroboration of the vinyl groups. The hydroboration products rearranged quickly and quantitatively by intramolecular 1,1-carboboration into the respective target compounds, the axially chiral 5-silaspiro[4.4]nona-1,6-dienes bearing boryl groups at the 2- and 7-positions and the R substituents at the 1- and 6-positions. Simple protodeborylation with acetic acid proved possible, except for R = tBu. The remaining Si–C function in (CH2=CH)2Si(Cl)C?CtBu opens the way to new spirosilanes after a sequence of hydroboration/carboboration/hydroboration, for which a first example was studied. The products were characterized by X-ray diffraction in the solid state and NMR spectroscopy in solution (1H, 11B, 13C, 15N, 29Si), complemented by optimization of gas-phase structures and calculation of NMR parameters by DFT methods. The dialkynyl(divinyl)silanes (CH2=CH)2Si(C?CR)2 and the alkynyl(chloro)(divinyl)silane (CH2=CH)2Si(Cl)C?CtBu are obtained from dichloro(divinyl)silane and converted into spirosilanes. The spirosilanes are used for successful protodeborylation reaction. The characteristic NMR spectroscopic data for all compounds are collected, and the X-ray structures of some examples are determined.

Posted on 16 June 2014 | 1:40 pm

The Impact of Anion-Modulated Structural Variations on the Magnetic Coupling in Trinuclear Heterometallic CuII–CoII Complexes Derived from a Salen-Type Schiff Base Ligand

Three new trinuclear heterometallic [(CuIIL)2CoIIX2] complexes [H2L = N,N?-bis(salicylidene)-1,3-propanediamine and X = thiocyanate (1), benzoate (2), or azide (3)] have been synthesized by reacting the metalloligand [CuL] with Co(ClO4)2·6H2O and the NH4+ or Na+ salt of the corresponding anion in methanol. Structural characterization reveals that the central CoII ion is connected to two terminal metalloligands through ?1,1-diphenoxido bridges in all three complexes. However, two monodentate thiocyanato ions, which are mutually cis coordinated to the Co atom in 1, generate a “bent” structure, whereas the trans-coordinated syn–syn bridging benzoato (1?O:2?O?) and the end-on bridging azido (?1,1) coligands in 2 and 3, respectively, produce linear structures. The changes in the number and nature of the bridges with a shortening of the distances between the metal centers leads to a concomitant decrease of the average CuII–O–CoII bridging angle from 99.3(2) to 97.1(4) and 91.5(1)° for 1, 2 and 3, respectively. Variable-temperature magnetic susceptibility measurements show the presence of a dominant antiferromagnetic coupling between the Cu–Co pairs in all three complexes. However, a steady decrease of the magnitude of the exchange coupling constant (JCu-Co) is observed from –33.4 (for 1) to –11.4 (for 2) and –2.15 cm–1 (for 3). This trend suggests that larger Cu–O–Co angles are associated with stronger antiferromagnetic coupling. Anion-mediated geometrical variations generate three heterometallic complexes with distinct trinuclear Cu2Co cores as a result of different diphenoxido bridging angles between the CuII and CoII ions. Magnetic studies reveal decreased antiferromagnetic exchange interactions associated with a decrease of this bridging angle.

Posted on 16 June 2014 | 1:30 pm

Nuclear Magnetic Resonance Spectroscopy of Aqueous Plutonium(IV) Desferrioxamine B Complexes

Two aqueous PuIV-desferrioxamine B (DFOB) complexes were characterized by one- and two-dimensional NMR techniques and an unexpected dimeric PuIVDFOB-di-?-(O/OH)-PuIVDFOB complex was identified. Both “Curie” and “anti-Curie” behavior were observed for the dimeric species, yet the monomeric species only showed “anti-Curie” behavior. Diffusion ordered spectroscopy experiments showed an increase in particle size for the two species, which is indicative of a dimeric species. Bond lengths and coordination numbers estimated from X-ray absorption spectroscopy are consistent with the proposed structures. Two aqueous PuIV-desferrioxamine B (DFOB) complexes were characterized by 1D and 2D NMR techniques and a dimeric PuIVDFOB-di-?-(O/OH)-PuIVDFOB complex was identified. Both “Curie” and “anti-Curie” behavior were observed for the dimeric species, yet the monomer only showed “anti-Curie”. Bond lengths and coordination numbers estimated from X-ray spectroscopic analysis support the proposed structures.

Posted on 16 June 2014 | 1:30 pm

Mono- and Dinuclear Complexes of Tricarbonylrhenium(I) with 4-Methyl-2,2?-bipyridine-4?-carbonitrile

Novel mono- and dinuclear tricarbonylrhenium(I) complexes of formula [Re(Mebpy-CN)(CO)3Cl] (1), [Re(Mebpy-CN)(CO)3(CH3CN)](PF6) (2), and [(CH3CN)(CO)3Re(Mebpy-CN)Ru(NH3)5](PF6)3 (3), in which Mebpy-CN = 4-methyl-2,2?-bipyridine-4?-carbonitrile, were prepared and characterized by spectroscopic, photophysical, and computational techniques. The complete structure of complex 2 was determined by X-ray diffraction. The increased conjugation in the bipyridyl ring owing to the nitrile substituent increases the emission quantum yields of the 3MLCT (metal-to-ligand charge-transfer) lowest-lying excited states of 1 and 2 with respect to the corresponding bpy complexes (bpy = 2,2?-bipyridine). The mixed-valent species of formula [(CH3CN)(CO)3Re(Mebpy-CN)Ru(NH3)5]4+ (4) was prepared in situ and as a mixed salt; the charge recombination from its metal-to-metal charge-transfer (MMCT) excited state is predicted to lie in the Marcus inverted region. The electronic structures and optical properties of all the reported complexes calculated by DFT and TD-DFT methods agree reasonably well with experimental results. Mono- and dinuclear tricarbonylrhenium(I) complexes of formula [Re(Mebpy-CN)(CO)3Cl] (1; Mebpy-CN = 4-methyl-2,2?-bipyridine-4?-carbonitrile), [Re(Mebpy-CN)(CO)3(CH3CN)](PF6) (2), [(CH3CN)(CO)3Re(Mebpy-CN)Ru(NH3)5](PF6)3 (3), and [(CH3CN)(CO)3Re(Mebpy-CN)Ru(NH3)5]4+ (4) were prepared and characterized by spectroscopic, photophysical, and computational techniques.

Posted on 13 June 2014 | 11:10 am

Vanadium Complexes as Prospective Therapeutics: Structural Characterization of a VIV Lysozyme Adduct

The biological activity of vanadium complexes, namely, as insulin enhancers, is well known. We report a combined X-ray crystallography, electron paramagnetic resonance, and density functional theory study of the interaction of vanadium picolinate complexes with hen egg white lysozyme (HEWL). We show that the VIVO(pic)2 complex covalently binds to the COO– group of the side chain of Asp52 of HEWL. The long VIV=O bond obtained in the X-ray study is explained to be due to reduction of VIV to VIII during exposure of the crystals to the intense X-ray beam. Vanadium complexes are recognized as insulin enhancers that can be transported by high-molecular-mass serum components. We report studies of the interaction of the antidiabetic vanadium(IV) picolinate complex with hen egg white lysozyme (HEWL). Soaked crystals diffracting up to a resolution of 1.28 Å show that VIV covalently binds to Asp52, two picolinate– ions (pic), and an Ooxido atom.

Posted on 4 June 2014 | 5:20 pm

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