Heterovalent trinuclear Co(III)-Co(II)-Co(III) complexes with N-(2-Carboxyethyl)salicylaldimines

The heterovalent trinuclear cobalt complexes [Co₂^IIIL₄ ⁱ · Co^II(H₂O)₄] · nXmY (L ⁱ are deprotonated Schiff bases derived from substituted salicylaldehydes and β-alanine; i = 1–3) were obtained and characterized. An X-ray diffraction study of the trinuclear cobalt complex with N-(2-carboxyethyl)salicylaldimine showed that the central Co(II) ion and the terminal Co(III) ions are linked by bridging carboxylate groups. Either terminal Co(III) atom is coordinated to two ligand molecules. They form an octahedral environment consisting of two azomethine N atoms, two phenolate O atoms, and two O atoms of two carboxylate groups. The central Co(II) atom is coordinated to four water molecules and to two O atoms of two bridging carboxylate ligands involved in the coordination sphere of the terminal Co(III) atoms.     

Thiocyanato-copper(II) complexes derived from a tridentate amine ligand and from alanine

Two thiocyanato-Cu(II) complexes including mononuclear dithiocyanato Cu(Me₃dpt)(NCS)₂ (1) and the polymeric 1D [Cu(d,l-Ala)(μ_N,S–NCS)(H₂O)] _n (2) were synthesized and structurally characterized (Me₃dpt = bis(N-methyl-3-propyl)methylamine, Ala = alaninate anion). The IR spectrum of complex 1 confirmed the N-bonding coordination mode of the thiocyanate groups, and its visible spectrum revealed the square pyramidal geometry around the central Cu²⁺ ion. Single X-ray crystallography of 1 showed that the Cu(II) center displays square pyramidal geometry with severe distortion toward trigonal bipyramidal environment. Complex 2 forms a 1-D polymeric chain with the NCS⁻ acting as a μ_N,S-ligand. A distorted SP geometry around the Cu²⁺ centers was achieved by the O and N atoms of alaninato anion, the aqua ligand and by the N and S atoms of the bridging thiocyanate groups. Hydrogen bonds of the type N–H···O, N–H···S and O–H···O are formed in this complex leading to the extension of the 1D chain to a supramolecular network.     

Complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 4-chloro-2-methoxybenzoic acid anion

The complexes of 4-chloro-2-methoxybenzoic acid anion with Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ were obtained as polycrystalline solids with general formula M(C₈H₆ClO₃)₂·nH₂O and colours typical for M(II) ions (Mn – slightly pink, Co – pink, Ni – slightly green, Cu – turquoise and Zn – white). The results of elemental, thermal and spectral analyses suggest that compounds of Mn(II), Cu(II) and Zn(II) are tetrahydrates whereas those of Co(II) and Ni(II) are pentahydrates. The carboxylate groups in these complexes are monodentate. The hydrates of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) heated in air to 1273 K are dehydrated in one step in the range of 323–411 K and form anhydrous salts which next in the range of 433–1212 K are decomposed to the following oxides: Mn₃O₄, CoO, NiO and ZnO. The final products of decomposition of Cu(II) complex are CuO and Cu. The solubility value in water at 293 K for all complexes is in the order of 10^–3 mol dm^–3. The plots of χ_M vs. temperature of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) follow the Curie–Weiss law. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in these complexes were determined in the range of 76−303 K and they change from: 5.88–6.04 μ_B for Mn(C₈H₆ClO₃)₂·4H₂O, 3.96–4.75 μ_B for Co(C₈H₆ClO₃)₂·5H₂O, 2.32–3.02 μ_B for Ni(C₈H₆ClO₃)₂·5H₂O and 1.77–1.94 μ_B for Cu(C₈H₆ClO₃)₂·4H₂O.     

Synthesis and characterization of zinc(II) and cobalt(III) Schiff base complexes

Two mononuclear complexes with the Schiff base ligand 2-((2-(dimethylamino)ethylimino)methyl)phenol (HL), namely ZnL₂ and CoL₂(N₃), have been synthesized and characterized using single-crystal X-ray diffraction and spectroscopy (IR, ¹H NMR, UV–Vis, MS and EA). Both complexes are mononuclear. The coordination geometry in the Zn(II) complex is distorted square-pyramidal with a weak Zn···N interaction. The Co(III) complex is distorted octahedral, and the neutral molecule unit [Co^IIIL₂(N₃)] is connected by C–H···N hydrogen bonds to form a one-dimensional infinite chain. The luminescence of the zinc compound has been investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Self-assembly of a Co(II) dimer through H-bonding of water molecules to a 3D open-framework structure

Reaction of pyridine-2,4,6-tricarboxylic acid (ptcH₃) with Co(NO₃)2.6H₂O in presence of 4,4′-bipyridine (4,4′-bpy) in water at room temperature results in the formation of [Co₂(ptcH)₂(4,4′-bpy) (H₂O)4]·2H₂O, (1). The solid-state structure reveals that the compound is a dimeric Co(II) complex assembled to a 3D architecture via an intricate intra- and inter-molecular hydrogen-bonding interactions involving water molecules and carboxylate oxygens of the ligand ptcH^2-. Crystal data: monoclinic, spacegroup P2 ₁/c, a = 11·441(5) ?,b = 20·212(2) ?,c = 7·020(5) ?, Β = 103·77(5)°,V= 1576-7(1) ?³,Z = 2,R1 = 00363,wR2 = 0·0856,S = 1·000.     

Synthesis, crystal structures and properties of the novel mononuclear copper(II) and tetranuclear cobalt(II) complexes with 3,6-bis-(3,5-dimethylpyrazolyl)-pyridazine

A novel monomer copper(II) complex [Cu(L)₂(SCN)] · ClO₄ (1) and a tetranuclear cobalt(II) complex [Co₄(L)₄(N₃)₄](OH)₄ · 2H₂O (2)(L = 3,6-bis-(3,5-dimethylpyrazolyl)-pyridazine) have been synthesized and structurally characterized. Single crystal X-ray analyses show that the Cu(II) atom is in a distorted trigonal bipyramidal coordinated environment consisting of four N atoms of L and one N atom of SCN⁻ in complex (1), and the monomer is extended to a 1D chain by the weak intermolecular π...π stacking interactions. In the complex (2), four Co(II) atoms are linked by four bridging azido groups in μ-1,1-N₃ (end-on) coordination mode to form a tetranuclear configuration. The fungicidal activity of the title compounds have been studied, and the results show that there are certain activities against several bacteria for the complexes and the ligand. Furthermore, two complexes exhibit blue emission fluoresce in the solid state at room temperature.     

Complexes of Co(II), Ni(II), and Cu(II) chlorides and bromides with tetrazol-1-yl-tris(hydroxymethyl)methane: Synthesis and structure

The reactions of Co(II), Ni(II), and Cu(II) chlorides and bromides and their metallic powders with tetrazol-1-yl-tris(hydroxymethyl)methane (L) afforded new complexes ML₂Hal₂ · mH₂O(M = Co(II) or Ni(II), Hal = Cl⁻; M = Cu(II), Hal = Cl⁻ or Br⁻, m = 0; and M = Co(II) or Ni(II), Hal = Br⁻, m = 2), MLnCl₂ (M = Co(II) or Ni(II), n = 2 or 4; M = Cu(II), n = 2), and MLnBr₂ · mH₂O (M = Ni(II), n = 2, m = 2; M = Cu(II), n = 2, m = 0). The compositions and structures of the synthesized complexes were determined by elemental analysis, IR spectroscopy (50–4000 cm⁻¹), and X-ray diffraction analysis. The introduction of a bulky substituent into position 1 of the tetrazole cycle was shown to exert almost no effect on the coordination mode but affected the composition and structure of the complexes.     

Spectral and Thermal Studies of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes with 3-methylglutaric Acid

Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 3-methylglutarates were prepared as solids with general formula MC₆ H₈ O₄ ×n H₂ O, where n =0–8. Their solubilities in water at 293 K were determined (7.0×10⁻² −4.2×10⁻³ mol dm⁻³ ). The IR spectra were recorded and thermal decomposition in air was investigated. The IR spectra suggest that the carboxylate groups are mono- or bidentate. During heating the hydrated complexes lose some water molecules in one (Mn, Co, Ni, Cu) or two steps (Cd) and then mono- (Cu) or dihydrates (Mn, Co, Ni) decompose to oxides directly (Mn, Cu, Co) or with intermediate formation of free metals (Co, Ni). Anhydrous Zn(II) complex decomposes directly to the oxide ZnO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal and magnetic behaviour of 5-chloro-2-nitrobenzoates of Co(II), Ni(II) and Cu(II)

5-Chloro-2-nitrobenzoates of Co(II), Ni(II) and Cu(II) having formulae Co(C₇H₃O₄NCl)₂·3H₂O, Ni(C₇H₃O₄NCl)₂·3H₂O and Cu(C₇H₃O₄NCl)₂·2H₂O, were obtained as polycrystalline compounds. From the IR spectra analysis of complexes, sodium salt and according to the spectroscopic criteria the carboxylate ions seem bidentate groups. The complexes of Co(II) and Cu(II) lose the water of crystallization in one step at 363–523 K. The Ni(II) complex loses it in two stages in the ranges of 323–378 and 378–523 K, respectively. The compounds follow the Curie–Weiss law. The magnetic moment values experimentally determined change from 4.53 to 4.55 μ_B for Co(II) complex, from 2.34 to 2.97 μ_B for Ni(II) 5-chloro-2-nitrobenzoate and from 1.80 to 1.90 μ_B for Cu(II) complex.     

Synthesis, structural characterization and thermal properties of three copper(II) complexes based on aryl hydrazide ligands

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu₃L₂¹(py)₄Cl₂] (1), [Cu(HL²)py] (2) and [Cu(HL³)py] (3), (H₂L¹ = 1-picolinoylthiosemicarbazide, H₃L² = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H₃L³ = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu₃ skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 ?³ are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.     

Three New Thioantimonates(V): Solvothermal Syntheses and Crystal Structures of [M(chxn)3]3(SbS4)2·4H2O (M = Ni,Co) and [Co(dien)2][Co(tren)SbS4]2·4H2O

The three new thioantimonates(V) [Ni(chxn)₃]₃(SbS₄)₂·4H₂O ( I ), [Co(chxn)₃]₃(SbS₄)₂·4H₂O ( II ) (chxn is trans‐1,2‐diaminocyclohexane) and [Co(dien)₂][Co(tren)SbS₄]₂·4H₂O ( III ) (dien is diethylenetriamine and tren is tris(2‐aminoethyl)amine) were synthesized under solvothermal conditions. Compounds I and II are isostructural crystallizing in space group C2/c. The structures are composed of isolated [M(chxn)₃]²⁺ complexes (M = Ni, Co), [SbS₄]^3? anions and crystal water molecules. Short S···N/S···O/O···O separations indicate hydrogen bonding interactions between the different constituents. Compound III crystallizes in space group and is composed of [Co(dien)₂]²⁺ and [Co(tren)SbS₄]^? anions and crystal water molecules. In the cationic complex the Co²⁺ ion is in an octahedral environment of two dien ligands whereas in [Co(tren)SbS₄]^? the Co²⁺ ion is in a trigonal bipyramidal coordination of four N atoms of tren and one S atom of the [SbS₄]^3? anion, i.e., two different coordination polyhedra around Co²⁺ coexist in this compound. Like in the former compounds an extended hydrogen bonding network connects the complexes and the water molecules into a three‐dimensional network.     

Co(II) and Cu(II) Schiff base complexes of bis(<Emphasis Type="Italic">N</Emphasis>-(4-diethylamino-2-methylphenyl)-3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylsalicylaldimine): Electrochemical and X-ray structural study

Copper(II) and cobalt(II) complexes of salicylaldimine obtained by the condensation of N,N-diethyl-2-methyl-1,4-phenylenediamine with 3,5-di-tert-butyl-2-hydroxybenzaldehyde have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, cyclic voltammetry, and FT-IR and UV–Vis spectroscopy. The molecular structure of the title copper(II) complex was determined by the single crystal X-ray diffraction technique. The Cu(II) center is coordinated by four atoms of the donor set in a compressed tetrahedral trans-[N₂O₂] environment, which can be essentially ascribed to the presence of bulky fragments of the ligand. The computed bond valences of the copper verify +2 oxidation state and indicate that the copper bonds, in particular Cu–N bonds, are elongated due to steric effects from bulky substituents in the ligands, N-(4-diethylamino-2-methylphenyl). Intermolecular C–H···π interactions leading to centrosymmetric synthons serve to stabilize periodic organization of the molecules.     

Solid state kinetics of Cu(II) complex of [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] from thermo gravimetric analysis

The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)₂]·2H₂O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min⁻¹ under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters such as order of reaction (n), activation energy (E _a), frequency factor (Z) and entropy of activation (∆S ^≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako (J Phys Chem 72(7):2406–2411, 1968).     

Investigation of the interaction between Co sulfide coatings and Cu(I) ions by cyclic voltammetry and XPS

The interaction between the Co sulfide coating formed on a glassy carbon electrode and Cu(I)-ammonia complexes solution was investigated by cyclic voltammetry in 0.1 M KClO₄, 0.1 M NaOH and 0.05 M H₂SO₄ solutions. It was determined that, after treating the cobalt sulfide coating formed by two deposition cycles with Cu(I)-ammonia complexes (0.4 M, pH 8.8–9.0, τ=180 s, T=25±1°C), an exchange occurs between the coating components and Cu(I). Copper(I) substitutes 75% of the Co(III) compounds present in the coating (~1.81×10^–7 mol cm^–2) because of Cu₂O (1.36×10^–7 mol cm^–2) formation. The rest of the Co(II) and Co(III) sulfide compounds are also replaced by copper with formation of Cu_{2– x} S with a stoichiometric coefficient close to 2 (~1.9). After modifying the cobalt sulfide coatings with Cu(I) ions, the total amount of metal (Co+Cu) increases, owing to the sorption of Cu(I) compounds. In addition, the number of deposition cycles decreases from 3 to 1.5 [1 cycle involves cobalt sulfide layer formation and 0.5 cycle is attributed to modifying by Cu(I) ions]. The coatings modified in the above-mentioned manner may be successfully used for plastic electrochemical metallization as Cu_{2– x} S coatings formed by three deposition cycles. Electronic Publication     

Synthesis,characterization and biological activities of 3-methylbenzyl 2-(6-methyl pyridin-2-ylmethylene)hydrazine carbodithioate and its transition metal complexes

A tridentate nitrogen-sulfur Schiff base, 3-methylbenzyl 2-(6-methylpyridin-2-ylmethylene)hydrazine carbodithioate (6mpyS3M), was synthesized by condensation of 6-methylpyridine-2-aldehyde with S-3-methylbenzyldithiocarbazate. It crystallized in space group P 2₁/n. It displayed intermolecular N–H···N hydrogen bonding between the α-nitrogen and the pyridyl nitrogen. The thione sulfur is in a trans position with respect to the 6-methylpyridine fragment across the C–N bond but adopts a cis position with the 3-methylbenzyl fragment through the C–S bond. Octahedral complexes containing two 6mpyS3M ligands were prepared with Cu(II), Ni(II), Zn(II) and Cd(II). 6mpyS3M and its metal complexes were assayed against selected microbes and two breast cancer cell lines. 6mpyS3M was strongly active against both cancer cell lines. Its metal complexes showed high selectivity with Cu(II), Ni(II) and Zn(II) complexes strongly active against only one of the cancer cell lines, whereas the Cd(II) complex was strongly active only against the other. Only Cu(II) and Cd(II) complexes were active against some of the bacteria.     

Studies on solid state synthesis and the oxygenation property of cobalt (II) Schiff base (vanilline polyamine) complexes

Three new cobalt complexes were synthesized by solid-state reaction at room temperature and the resultant Co complexes reacted with two equivalent oxygen molecules at room temperature to produce the oxygenated complexes [Co·(L₁)₂·(O₂)₂](NO₃)₂·2H₂O (L₁ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-diethylenetriamine), [Co·(L₂)₂·(O₂)₂](NO₃)₂·2H₂O (L₂ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-triethylenetetramine), and [Co·(L₃)₂·(O₂)₂](NO₃)₂·2H₂O (L₃ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl-tetraethylenepentamine). The oxygenated complexes were characterized by elemental analysis, IR (Infrared), ¹H-NMR (Nuclear Magnetic Resonance), and UV-Vis (Ultraviolet Visual) spectrometry, and TG/DTA (Thermogravimetry/Differential Thermal Analysis) analysis, and molar conductance. The coordinated oxygen contents in the oxygenated complexes were also determined by weight method. It was supposed that only one O₂ molecule coordinated to the Co ion forming a superoxo type oxygenated complex. Translated from Acta Chimica Sinica, 2006, 64(15): 1517–1522 (in Chinese)     

Polymeric and monomeric dipicolinate complexes with 4-hydroxymethyl pyridine: spectral, structural, thermal and electrochemical characterization

Polymeric copper(II), [Cu(μ-dpc)(μ-4-hymp)] _n (1), and monomeric nickel(II), [Ni(dpc)(4-hymp)(H₂O)₂]·H₂O (2), (dpc: dipicolinate, 4-hymp: 4-hydroxymethyl pyridine), dipicolinate complexes have been prepared and characterized by spectroscopic (IR, UV–Vis, EPR), thermal (TG/DTA), X-ray diffraction technique and electrochemical methods. In both the dipicolinate complexes, the dpc dianion acts as a tridentate ligand. In polymeric copper(II) complex, the 4-hymp and dpc ligands adopt a bridging position between the Cu(II) centers, forming the elongated octahedral geometry. The polymeric chains are linked to one another via O–H···O hydrogen bond interactions, forming the 3-D polymeric structure. The Ni(II) ion is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of 4-hymp, forming the distorted octahedral geometry. The Ni(II) complexes are connected to one another via O–H···O hydrogen bonds, forming R ₄²(18) motifs in 2-D pattern. The powder EPR spectra of copper(II) complex have indicated that the paramagnetic center is in rhombic symmetry with the Cu²⁺ ion having distorted octahedral geometry. IR and UV–Vis spectroscopes all agree with the observed crystal structure.     

Kinetics of oxidation of N,N-bis(salicylaldehyde-1,2-diaminoethane) cobalt(II) complex by periodate. Evidence for the inhibiting effect of copper(II)

A kinetic study of the oxidation of [Co(H₂L)(H₂O)₂]²⁺ (H₂L = N,N-bis (salicylaldehyde-1,2-diaminoethane) Schiff base) by periodate in aqueous solution was performed over pH (2.3–3.4) range, (0.1–0.5) mol dm⁻³ ionic strength and temperatures 20–35 °C for a range of periodate and complex concentrations. The reaction rate showed a first-order dependence on both reactants and increased with pH over the range studied. The effects of Cu(II) and Fe(II) on the reaction rate were investigated over the (1.0–9.0) × 10⁻⁵ mol dm⁻³ range. The reaction was inhibited as the concentration of Cu(II) increased, and it was independent on Fe(II) concentrations over the ranges studied. An inner-sphere mechanism is proposed for the oxidation pathways of both the protonated and deprotonated Co^II complex species.     

Acenaphthylene-1,2-diamine radical cation. Molecular structure of the [(dpp-BIAN)H2]·+[X]− complex ((dpp-BIAN)H2 is N,N′-bis(2,6-diisopropylphenyl)-acenaphthylene-1,2-diamine; X = Cl or I)

Oxidation of N,N′-bis(2,6-diisopropylphenyl)acenaphthylene-1,2-diamine (dpp-BIAN)H₂ with silicon tetrachloride or mercury(II) chloride affords the [(dpp-BIAN)H₂]·⁺[Cl]⁻ compound. The corresponding iodine derivative, [(dpp-BIAN)H₂]·⁺[I]⁻, was prepared by hydrolysis of the reaction products of the magnesium complex (dpp-BIAN)Mg(THF)₃ with tetraiodosilane. X-ray diffraction study demonstrated that the [(dpp-BIAN)H₂]^·+ radical cation in these compounds chelates the corresponding halide anion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 436–440, March, 2006.     

Cobalt(II) and nickel(II) complexes of isoquinoline‐1‐carboxylate

trans‐Di­aqua­bis­(iso­quinoline‐1‐carboxyl­ato‐κ²N,O)­cobalt(II) dihydrate, [Co(C₁₀H₆NO₂)₂(H₂O)₂]·2H₂O, and trans‐di­aqua­bis­(iso­quinoline‐1‐carboxyl­ato‐κ²N,O)­nickel(II) dihydrate, [Ni(C₁₀H₆NO₂)₂(H₂O)₂]·2H₂O, contain the same isoquinoline ligand, with both metal atoms residing on a centre of symmetry and having the same distorted octahedral coordination. In the former complex, the Co—O(water) bond length in the axial direction is 2.167 (2) Å, which is longer than the Co—O(carboxylate) and Co—N bond lengths in the equatorial plane [2.055 (2) and 2.096 (2) Å, respectively]. In the latter complex, the corresponding bond lengths for Ni—O(water), Ni—O(carboxylate) and Ni—N are 2.127 (2), 2.036 (2) and 2.039 (3) Å, respectively. Both crystals are stabilized by similar stacking interactions of the ligand, and also by hydrogen bonds between the hydrate and coordinated water molecules.