A novel mixed-valence vanadium(IV/V) complex containing linear mono-μ-oxo [V3O5]4+ core

A novel trinuclear V^V/IV/V complex, [VO₂(phen)(SO₄)(H₂O)]₂[VO(phen)(H₂O)]} (1), containing linear mono-μ-oxo [V₃O₅]⁴⁺ core was prepared and characterized by single-crystal X-ray diffraction. Complex 1 represents the first mixed-valence polynuclear vanadium complex with linear mono-μ-oxo-vanadium/vanadyl core. Furthermore, the study of the EPR and electronic spectrum of complex 1 show that it is a Class II species according to the Robin and Day classification scheme.     

A tetranuclear oxomolybdenum(V) complex with bridging squarate ligands, [MoV4O8(OH)2(H2O)2(C4O4)2]2−

The new tetranuclear polyoxomolybdate(V) ion [Mo^V₄O₈(OH)₂(H₂O)₂(C₄O₄)₂]²⁻ has been obtained in one step by the reaction of sodium molybdate, hydrazine and squaric acid in water and crystallized as a potassium salt. The structure has been solved by single-crystal X-ray diffraction showing the location of the hydroxo and water molecule ligands.     

A novel 12-tungstovanadate and 3d–4d heterometallic complex hybrid compound [V1W12O40][VO2Ag(phen)3]2

A novel organic–inorganic hybrid compounds containing 12-tungstovanadate and 3d–4d heterometallic complex, [V₁W₁₂O₄₀][VO₂Ag(phen)₃]₂ (1), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction and IR analysis. The complex is an uncommon bisupporting polyoxometalate derivative in which the saturated Keggin type polyoxoanions are covalently linked by bimetallic complex [VO₂Ag(phen)₃]²⁺. The neighboring Ag⁺ and V⁵⁺ cations are bridged by the oxo atom forming heterometallic cations with the Ag–V distances of 3.556(2) Å in [VO₂Ag(phen)₃]²⁺ cations. Furthermore, the title compound shows good photocatalytic activity for reduction of Rhodamine B (RB) in a liquid–solid system.     

A new polymeric chain in the dihydrogendecavanadate(V)–decavanadate(V) [NH2(CH2)4]5[V10O28H2]0.5[V10O28]0.5 obtained by in situ synthesis of the organic cation

A new polymeric compound, [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5, was obtained by in situ synthesis of the organic cation from an aqueous solution of V₂O₅–HCl–NH₂(CH₂)₄NH₂. The crystal structure was solved by single-crystal X-ray diffraction. [NH₂(CH₂)₄]₅[V₁₀O₂₈H₂]_0.5[V₁₀O₂₈]_0.5 consists of dihydrogendecavanadate(V), [H₂V₁₀O₂₈]^4?, and decavanadate(V), [V₁₀O₂₈]^6?, units assembled in one-dimensional arrays by interanionic hydrogen bonds O–H?O and cation-anion N–H?O interactions. The latter involve pyrrolidinium cations, which were obtained in the compound instead of the starting butane-1,4-diamine. Pyrrolidinium cations further connect the polymeric chains into a three-dimensional network. The presence of the two types of units, [H_nV₁₀O₂₈]^(6?n)? with n = 0 and n = 2, in one compound was not yet observed and is herein reported for the first time.     

MLCT interaction in [Rh(II)2(CO3)4]4 −( x L)

Complexes of the type [Rh^II₂(CO₃)₄(H₂O)L]^n − with L = N-methylpyrazinium⁺ and 1-heptyl-4-(4-pyridinyl)pyridinium⁺ cations display intense long-wavelength (Rh(II) to L) MLCT absorptions. With L = H₂O, MLCT absorptions are not identified, but the photoreactivity of the complex in aqueous solution supports the assumption that (Rh(II) to CO₃^2 −) MLCT excited states are accessible. Upon irradiation with white light, Rh(II) is photooxidized while carbonate is reduced to CO. The efficiency of this photolysis is very low. However, the occurrence of this photoredox reaction is, nevertheless, of general interest with regard to the photochemical reduction of CO₂.     

Trans,trans,trans-[ReO2I2(PPh3)2], a rare rhenium(VI) complex — Synthesis and DFT study

The heating of cis-[ReO₂I(PPh₃)₂] at reflux in benzene in air led to the isolation of the rhenium(VI) complex [ReO₂I₂(PPh₃)₂] (1). The compound is centrosymmetric around the octahedrally coordinated rhenium center, and the ReO bond length of 1.797(2) Å is longer than in typical trans-dioxorhenium(V) complexes. The asymmetric ReO stretching frequency occurs at 744 cm^− 1. Density functional theory has been used for the calculation of the vibrational spectrum density which confirms the experimental asymmetric ReO stretching frequency. DFT calculation within the polarizable continuum model shows that complex 1 is more stable in CH₂Cl₂ than in the gas phase. EPR spectroscopy confirms a single d electron in 1. The crystal structure was determined by X-ray single crystal diffraction. In addition, infra-red, redox and electronic properties are also reported.     

Synthesis,structure, and properties of two novel copper(II) complexes, [Cu(phen)(L)2]·6H2O and [Cu(phen)3]·(ClO4)2

Two novel copper(II) complexes, namely [Cu(phen)(L)₂]·6H₂O (1) and [Cu(phen)₃]·(ClO₄)₂ (2) have been synthesized under mild condition (HL = 5-methyl-1H-pyrazole-3-carboxylic acid, phen = 1,10-phenanthroline). We report the structural evidence of discrete water decamer conformation in the solid state. These units are found to act as supramolecular glue in the aggregation of mononuclear copper(II) complex to give a three-dimensional network through hydrogen-bonding. The preliminary investigation on the thermal behavior and the anion exchange property of the complexes are presented.     

Synthesis of cis- and trans-[M(CN)2(1-CH3-C6H10-NC)4] (M = Fe,Ru) and crystal structure of trans-[Ru(CN)2(1′-CH3-C6H10-NC)4]

The reaction of the metal carbonyls Fe₂(CO)₉ or Ru₃(CO)₁₂ with 1-isocyano-1-methyl-cyclohexane produces the octahedral metal(II) cyano complexes [M(CN)₂(1-CH₃-C₆H₁₀-NC)₄] in good yields. The cis-isomer is not isolated as a pure compound due to rearrangement processes that yield the sterically less crowded trans-isomer. The molecular structure of the trans-isomer of the ruthenium complex shows the expected almost ideal octahedral coordination of the central ruthenium ion with two cyanide and four isocyanide ligands. This reaction again indicates that isocyanides exhibiting quarternary carbon atoms in α-position with respect to the isocyano substituent in general react with di- or trinuclear metal carbonyls to yield cyano complexes with oxidized metal centres and concomitant reductive cleavage of the respective isocyanide.     

Synthesis,structure and superoxide dismutase activity of a novel tetranuclear copper(II) complex Na2[Cu4Na2(TACNTA)4(H2O)6]·(H2O)26

A novel tetranuclear copper(II) complex Na₂[Cu₄Na₂(TACNTA)₄(H₂O)₆]·(H₂O)₂₆, where TACNTA is 1,4,7-triazacyclononane-1,4,7-triacetate, was synthesized and characterized by X-ray crystallography. The result shows that each copper(II) ion is six-coordinated to three nitrogen atoms and three oxygen atoms of ligand TACNTA and adopts distorted octahedral coordination geometry. The superoxide (·O₂^?) dismutation activity of the complex was also investigated by the riboflavin–methionine–nitro blue tetrazolium assay.     

Hydrothermal synthesis,crystal structure,spectroscopy, electrochemistry and antimycobacterial evaluation of the copper (II) ciprofloxacin complex: [Cu(cf)2(BF4)2]·6H2O

The hydrothermal reaction of ciprofloxacin (1) with Cu(BF₄)₂·6H₂O yields a copper complex having a molecular formula, [Cu(cf)₂(BF₄)₂]·6H₂O (cf = ciprofloxacin), which is characterized by spectroscopic and electrochemical measurements as well as single crystal X-ray studies [a=9.1079(13), b=9.6112(16), c=11.4542(18) Å, α=90.518 (19)°, β=99.160 (18)°, γ=93.315 (19)°, P1bar, Z=1]. The F₂O₄ donor atom set forms a (4+2) distorted octahedral geometry around the central copper atom; which has a highly facile copper redox couple (+0.23 V). The copper conjugate exhibits a significant enhancement in the antitubercular activity probably arising out of its rapid intracellular reduction leading to oxygen activation, which is detrimental to the mycobacteria.     

Hetero-Metallic Coordination Polymers: Syntheses, Vibrational Spectra, Thermal Analyses and Crystal Structures of trans-[M(N-Meim)2Ni(μ–CN)4] n (M=Cu(II), Zn(II) and Cd(II))

Three cyano bridged hetero-metallic complexes of general formula, trans-[M(N-Meim)₂Ni(μ-CN)₄] _n (N-Meim=N-methylimidazole and M=Cu(II), Zn(II) or Cd(II)) have been synthesized and characterized by vibrational (FT-IR and Raman) spectroscopy, single crystal X-ray diffraction, thermal analyses and elemental analyses. The crystallographic analyses reveal that the complexes, [Cu(N-Meim)₂Ni(μ-CN)₄] _n (1), [Zn(N-Meim)₂Ni(μ-CN)₄] _n (2) and [Cd(N-Meim)₂Ni(μ-CN)₄] _n (3), have polymeric 2D networks. In the complexes, four cyanide groups of [Ni(CN)₄]²⁻ coordinated to the adjacent M(II) ions and distorted octahedral geometries of complexes are completed by two nitrogen atoms of trans N-Meim ligands. Vibration assignments are given for all the observed bands and the spectral features also supported to the crystal structures of polynuclear complexes.     

Cyano-Bridged Heteropolynuclear Ni(II), Cu(II) and Cd(II) Complexes, [M(deten)2Ni(μ-CN)2(CN)2] n

Three new complexes [M(deten)₂Ni(μ-CN)₂(CN)₂] _n (M = Ni, Cu and Cd, deten = N,N-diethylethylenediamine) have been synthesized and characterized by chemical, thermal analysis, FT-IR and Raman spectroscopies. The crystal structure of the Cd complex has been determined by X-ray single crystal diffraction. Structural study reveals that the Ni²⁺ and Cd²⁺ ions are located on inversion centers, and adopt slightly distorted square-planar and octahedral geometries, respectively. In the crystal structure, the intermolecular N–H⋯N hydrogen bonds link the polymeric chains into a two dimensional network. Vibrational spectral data indicate the presence of two ν(C≡N) for complexes can be assigned to the terminal and bridging cyanides. The decomposition reaction take places in the temperature range 30–1000 °C in the static air atmosphere.     

[C16H33N(CH3)3]3[PO4(WO3)4]催化脂肪酸甲酯环氧化性能

在无酸、无溶剂条件下,以[C₁₆H₃₃N(CH₃)₃]₃[PO₄(WO₃)₄]为反应控制相转移催化剂,研究各因素对脂肪酸甲酯(FAME)环氧化反应的影响。结果表明,水相pH对环氧化反应的影响最大,反应适宜pH为4;适宜反应条件为过氧化氢与脂肪酸甲酯中双键摩尔比为1.05:1,反应温度50～60℃,反应时间5 h。在此反应条件下催化剂循环5次不失活,产品环氧值大于4.0%,碘值小于5 g I·(100 g)^-1。并通过元素分析与红外光谱,研究了催化剂在反应过程中的变化,认为磷钨杂多阴离子的分解是导致催化剂失活的关键原因。     

Tetra(o-phenyldiazo-p-methylphenoxy)silane – A silicon complex with a fourfold capped-tetrahedral [4+4] coordination sphere

2-Hydroxy-5-methylazobenzene (HO–C₆H₃-p-Me-o-NN–C₆H₅, 1) reacts with SiCl₄ in the presence of triethylamine to yield the [4+4]-coordinate silicon complex 2 [Si(O–C₆H₃-p-Me-o-NN–C₆H₅)₄]. Its molecular structure has been determined by X-ray crystallography, and 2 represents the first structurally characterized Si-complex bearing o-diazophenoxy ligands. ²⁹Si NMR data suggest that the capped tetrahedral coordination sphere of the Si-atom is retained in solution. Even the difluorocompound 3 [F₂Si(O–C₆H₃-p-Me-o-NN–C₆H₅)₂] still exhibits a tetracoordinate Si-atom, whereas 4 [F₂B(O–C₆H₃-p-Me-o-NN–C₆H₅)], the byproduct of the formation of 3 from 2, bears a bidentate chelating o-phenyldiazo-p-methylphenoxy ligand.     

Synthesis,crystal structure and magnetic properties of one-dimensional cyano-bridged bimetallic complex of [Mn(Me2-bipy)2]3[W(CN)8]2·9H2O

An octacyanotungstate(V)-manganese(II) bimetallic assembly [Mn(Me₂-bipy)₂]₃[W(CN)₈]₂·9H₂O (1) (Me₂-bipy = 4,4′-dimethyl-2,2′-bipyridine) was synthesized in methanol and characterized by X-ray crystallography. X-ray analysis shows that complex 1 is a neutral, one-dimensional (1D) infinite chain polymer. Magnetic data analysis demonstrates a long-range magnetic interaction and two different antiferromagnetic coupling constants obtained by fitting between Mn and W ions in 1.     

Synthesis,structure and properties of a new copper (II) complex, [Cu2(4,4′-bpy)5(H2O)4](ClO4)4(4,4′-bpy)(DMF)2(H2O)2

A new copper (II) complex with formula [Cu₂(4,4′-bpy)₅(H₂O)₄](ClO₄)₄(4,4′-bpy)(DMF)₂(H₂O)₂ has been synthesized by reaction of 4,4′-bpyridine (4,4′-bpy) with Cu(ClO₄)₂. While strong hydrogen bonds play central roles in the formation of the 3D structure, the combined influence of the weak interactions such as C–H?O bonds, anion?π and C–H?π interactions are also evident in the structure. The preliminary investigation on the thermal property of the complex is presented.