Spectroscopic studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes with a N4-macrocylic ligands

Complexes of cobalt(II), nickel(II), copper(II) and zinc(II) with a new tetraaza macrocyclic ligand have been synthesized and characterized by microanalyses, molar conductance, magnetic susceptibility, mass, thermogravimetric (TGA), IR, 1H and 13C NMR, electronic and ESR spectral studies. All the complexes are found to have the formula [MLX2]x nH2O and are six-coordinated with distorted octahedral geometry.     

Transition Metal Complexes with Pyrazole-Based Ligands 7. Zn(II), Co(II), Mn(II) and Cu(II) complexes with 3-amino-5-methylpyrazole

Complexes represented by the general formula [MCl₂L₂] (M(II)=Zn, Mn, Co) and complexes of [Cu₃Cl₆L₄] and CuSO₄L₂·4H₂O, CoSO₄L₂·3H₂O, [ZnSO₄L₃] where L stands for 3-amino-5-methylpyrazole were prepared. The complexes were characterized by elemental analysis, FT-IR spectroscopy, thermal (TG, DTG, DSC and EGA) methods and molar conductivity measurements. Except for the Zn-complexes, the magnetic susceptibilities were also determined. Thermal decomposition of the sulphato complexes of copper(II) and cobalt(II) and the chloro complexes of cobalt(II) and manganese(II) resulted in well-defined intermediates. On the basis of the IR spectra and elemental analysis data of the intermediates a decomposition scheme is proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Thermal Decomposition of Mixed 2,4'-bipyridine-oxalato Complexes With Mn(II), Co(II), Ni(II) and Cu(II)

The mixed 2,4'-bipyridine-oxalato complexes of the formulae M(2,4'-bipy)₂ C₂ O₄ 2H₂ O (M (II)=Mn, Co, Ni, Cu; 2,4'-bipyridine=2,4'-bipy or L ; C₂ O^2– ₄ =ox) have been prepared and characterized. IR data show that the 2,4'-bipy coordinated with these metals(II) via the least hindered (4')N atom; that oxalate group acts as bidentate chelating ligand. Room temperature magnetic moments are normal for the orbital singlet states. The thermal decomposition of these complexes was investigated by TG, DTA and DTG in air. The endothermic or exothermic character of the decomposition of ML₂ (ox)2H₂ O was discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Complexes of Mn(II), Co(II), Ni(II) and Cu(II) with 4,4'-bipyridine and dichloroacetates

New mixed-ligand complexes with empirical formulae M(4-bpy)L₂·1.5H₂O (M(II)=Mn, Co), Ni(4-bpy)₂L₂ and Cu(4-bpy) L₂·H₂O (where: 4-bpy=4,4'-bipyridine, L=CC L2HCOO^-) have been isolated in pure state. The complexes have been characterized by elemental analysis, ir spectroscopy, conductivity (in methanol, dimethylformamide and dimethylsulfoxide solutions) and magnetic and x-ray diffraction measurements. The Mn(II) and Co(II) complexes are isostructural. The way of metal-ligand coordinations discussed. the ir spectra suggest that the carboxylate groups are bonded with metal(II) in the same way (Ni, Cu) or in different way (Mn, Co). The solubility in water is in the order of 19.40·10^-3÷1.88·10^-3ł mol dm^-3ł. During heating the hydrate complexes lose all water in one step. The anhydrous complexes decompose to oxides via several intermediate compounds. A coupled TG-MS system was used to analyse the principal volatile products of obtained complexes. The principal volatile products of thermal decomposition of complexes in air are: H₂O₂ ⁺, CO₂ ⁺, HCl⁺, Cl₂ ⁺, NO⁺ and other. This revised version was published online in July 2006 with corrections to the Cover Date.     

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 Properties of Complexes of Mn(II), Fe(II), Co(II), Ni(II) With 2,2'-bipyridine Or 4,4'-bipyridine and Thiocyanates

The compounds ML₂(NCS)₂, (M(II)=Mn, Co), FeL₂(NCS)₂×2H₂O, NiL₃ NCS)₂×3H₂O (L=2,2'-bipyridine, 2-bipy) MX₂(NCS)₂×2H₂O (M(II)=Mn, Fe; X=4,4'-bipyridine, 4-bipy) have been prepared and their IR spectra and molar conductivity studied. The thermal decomposition of the complexes was studied under non-isothermal conditions in air. During heating the hydrated complexes lose crystallization water molecules in one or two steps and then decompose via different intermediate compounds to the oxides Mn₃O₄, Fe₂O₃, CoO, NiO. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hetero-binuclear chelates of Mn(II), Co(II) and Cu(II) o-cresolphthalein complexonates with other metal ions

Heterobinuclear metal chelates of Mn²⁺, Co²⁺ or Cu²⁺ and some transition metal ions with o-cresolphthalein complexone have been prepared and characterized. Elemental analyses are in agreement with proposed formulae. Thermal analyses (TGA and DTA) were used to determine the degradation products; some thermodynamic parameters were calculated. IR and UV-Vis spectra identified the mode of bonding between the metal ions and the ligand as well as its geometry. Magnetic moment determination and ESR spectra of the heterobinuclear complex revealed some antiferromagnetic interaction between the metal ions, which depends mainly on the two metal ions forming the chelate. Electrochemical studies of the complexes [DC-polarography and cyclic voltammetry (CV)] confirmed the existence and the nature of the metal ions in the chelate.     

Study of the Thermal Decompositions on N,N-Dialkyl-N'-Benzoylthiourea Complexes of Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III)

The thermal decompositions of the complexes of N,N-dialkyl-N'-benzoylthioureas with Cu(II), Ni(II), Pd(II), Pt(II), Cd(II), Ru(III) and Fe(III) were studied by TG and DTA techniques. These metal complexes decompose in two stages: elimination of dialkylbenzamide, and total decomposition to metal sulphides or metals. The influence of the alkyl substituents in these benzoylthiourea chelates on the thermal behaviour of the metal complexes was investigated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Thermal, spectral and magnetic behaviour of 2,3,4-trimethoxybenzoates of Mn(II), Co(II), Ni(II) AND Cu(II)

Four new complexes of 2,3,4-trimethoxybenzoic acid anion with manganese(II), cobalt(II), nickel(II) and copper(II) cations were synthesized, analysed and characterized by standard chemical and physical methods. 2,3,4-Trimethoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II) are polycrystalline compounds with colours typical for M(II) ions. The carboxylate group in the anhydrous complexes of Mn(II), Co(II) and Ni(II) is monodentate and in that of Cu(II) monohydrate is bidentate bridging one. The anhydrous complexes of Mn(II), Co(II) and Ni(II) heated in air to 1273 K are stable up to 505–517 K. Next in the range of 505–1205 K they decompose to the following oxides: Mn₃O₄, CoO, NiO. The complex of Cu(II) is stable up to 390 K, and next in the range of 390–443 K it loses one molecule of water. The final product of its decomposition is CuO. The solubility in water at 293 K is of the order of 10^–3 mol dm^–3 for the Mn(II) complex and 10^–4 mol dm^–3 for Co(II), Ni(II) and Cu(II) complexes. The magnetic moment values of Mn²⁺, Co²⁺, Ni²⁺ and Cu²⁺ ions in 2,3,4-trimethoxybenzoates experimentally determined in the range of 77–300 K change from 5.64–6.57 μB (for Mn²⁺), 4.73–5.17 μB (for Co²⁺), 3.26–3.35 μB (for Ni²⁺) and 0.27–1.42 μB (for Cu²⁺). 2,3,4-Trimethoxybenzoates of Mn(II), Co(II) and Ni(II) follow the Curie–Weiss law, whereas that of Cu(II) forms a dimer.     

Salisaldehyde-2-aminobenzimidazole schiff base complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II)

New metal complexes of Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with salicylidine-2-aminobenzimidazole (SABI) are synthesized and their physicochemical properties are investigated using elemental and thermal analyses, IR, conductometric, solid reflectance and magnetic susceptibility measurements. The base reacts with these metal ions to give 1:1 (Metal:SABI) complexes; in cases of Fe(III), Co(II), Cu(II), Zn(II) and Cd(II) ions; and 1:2 (Metal:SABI) complexes; in case of Ni(II) ion. The conductance data reveal that Fe(III) complex is 2:1 electrolyte, Co(II) is 1:2 electrolyte, Cu(II), Zn(II) and Cd(II) complexes are 1:1 electrolytes while Ni(II) is non-electrolyte. IR spectra showed that the ligand is coordinated to the metal ions in a terdentate mannar with O, N, N donor sites of the phenloic -OH, azomethine -N and benzimidazole -N3. Magnetic and solid reflectance spectra are used to infer the coordinating capacity of the ligand and the geometrical structure of these complexes. The thermal decomposition of the complexes is studied and indicates that not only the coordinated and/or crystallization water is lost but also that the decomposition of the ligand from the complexes is necessary to interpret the successive mass loss. Different thermodynamic activation parameters are also reported, using Coats-Redfern method. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation,Properties and Thermal Decompositions of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes of 2,5-dichlorobenzoic Acid

Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) 2,5-dichlorobenzoates were prepared and their compositions and solubilities in water at 295 K were determined. The IR spectra and X-ray diffractograms of the obtained complexes were recorded. The complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) were obtained as solids with a 1:2 molar ratio of metal to organic ligand and different degrees of hydration. When heated at a heating rate of 10 K min^-1, the hydrated complexes lose some (Co, Zn) or all (Ni, Cu, Cd) of the crystallization water molecules and then decompose to oxide MO (Co, Ni) or gaseous products (Cu, Zn, Cd). When heated at a heating rate of 5 K min^-1, the complexes of Ni(II) and Cu(II) lose some (Ni) or all (Cu) of the crystallization water molecules and then decompose directly to MO. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis, thermal and other studies of 2,4'-bipyridine-dichloroacetato complexes of Mn(II), Co(II), Ni(II) and Cu(II)

Four new mixed ligand complexes were prepared by the reaction of title metal dichloroacetates and 2,4'-bipyridine. The general formulae of synthesized compounds are M(2,4'-bpy)₂(CCl₂HCOO)₂·nH₂O (where M(II)=Mn, Co, Ni, Cu; 2,4'-bpy=2,4'-bipyridine, n=2 or 4). The complexes have been isolated from aqueous media and characterized by chemical analysis, molar conductance (in MeOH, DMSO and DMF), magnetic, IR and VIS spectral studies. The nature of metal(II)-ligand coordination is discussed. The thermal behaviour of obtained complexes was studied by thermal analysis and TG-MS techniques in air. IR, X-ray powder diffraction and thermoanalytical data were used for the determination of solid intermediate products of the thermal decomposition. The principal volatile products of thermal decomposition of complexes were proved by mass spectroscopy: H₂O⁺, CO⁺ ₂, HCl⁺ ₂, Cl⁺ ₂, NO⁺ and other. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis,physico-chemical investigations and biological studies on Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with p -amino acetophenone isonicotinoyl hydrazone

Complexes of the type [M(painh)(H₂O)₂X], where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); X = Cl₂ or SO₄; painh = p-amino acetophenone isonicotinoyl hydrazone, have been synthesized and characterized by spectral and other physico-chemical techniques. The synthesized complexes are stable powders, insoluble in common organic solvents such as ethanol, benzene, carbon tetrachloride, chloroform and diethyl ether, and are non-electrolytes. Thermogravimetric Analysis (TGA) and Differential Thermal Analysis (DTA) studies show that the organic ligand decomposes exothermically through various steps. TGA and Infrared (IR) spectral studies indicate the presence of coordinated water in the metal complexes. Magnetic susceptibility measurements and electronic spectra suggest that Mn(II), Co(II), and Ni(II) complexes are paramagnetic with octahedral geometry, whereas Cu(II) complexes have distorted octahedral geometry. The neutral bidentate ligand bonds through >C=O and >C=N–groups in all the complexes. Electron Spin Resonance (ESR) spectra in the solid state show axial symmetry for [Cu(painh)(H₂O)₂(SO₄)] and elongated rhombic symmetry for [Cu(painh)(H₂O)₂Cl₂], suggesting an elongated tetragonally-distorted octahedral structure for both complexes. X-ray powder diffraction parameters for two complexes correspond to tetragonal and orthorhombic crystal lattices. The metal complexes show fair antifungal activity against Rizoctonia sp., Aspergillus sp., Stemphylium sp., and Penicillium sp. and appreciable antibacterial activity against Pseudomonas sp. and Escherichia coli.     

Synthesis and structural studies of complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with substituted chalcones

Complexes of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with 3-(2-pyridyl)-1-(2-hydroxy phenyl)-2-propen-1-one (PHPO), 3-(1-naphthyl)-1-(2-hydroxy phenyl)-2-propen-1-one (NHPO) and 3-(3,4-dimethoxy phenyl)-1-(2-hydroxy phenyl)-2-propen-1-one (DMPHPO) have been synthesized and characterized by analytical, conductivity, thermal, magnetic, infrared, electronic and electron spin resonance data. Based on analytical data the stoichiometry of the complexes has been found to be 1 : 2. The conductivity data show that all these complexes are non-electrolytes. The infrared spectral data indicate that the ligand PHPO acts as uninegative tridentately towards Co(II) and Ni(II) and bidentately with Cu(II), Zn(II) and Cd(II). Ligands like NHPO and DMPHPO act as uninegative bidentately with all the metal ions. The electronic spectral data suggest that all the Co(II) complexes and Ni(II) of PHPO complex are octahedral and all the Cu(II) and Ni(II) of NHPO and DMPHPO complex are square-planar. The complex of Zn(II) and Cd(II) are tetrahedral. ESR parameters of Cu(II) complexes have been calculated and relevant conclusions have been drawn with respect to the nature of bonds present in them.     

Thermal and Other Properties of New 4,4'-bipyridine-trichloroacetato Complexes of Mn(II), Ni(II) and Zn(II)

New mixed-ligand complexes of general formulae Mn(4-bpy)(CCl₃COO)₂⋅H₂O, Ni(4-bpy)₂(CCl³COO)₂⋅2H²O and Zn(4-bpy)₂(CCl₃COO)₂⋅2H²O (where 4-bpy=4,4’-bipyridine) were obtained and characterized. The IR spectra, conductivity measurements and other physical properties of these compounds were discussed. The central atoms M(II) form coordinate bonds with title ligands. The thermal behaviour of the synthesized complexes was studied in air. During heating the complexes decompose via different intermediate products to Mn₃O₄, NiO and ZnO; partial volatilization of ZnCl₂was observed. A coupled TG-MS system was used to the analysis of the principal volatile thermal decomposition products of Mn(II) and Ni(II) complexes. The principal volatile mass fragments correspond to: H₂O⁺, OH⁺, CO⁺ ₂, HCl⁺, Cl⁺ ₂, CCl⁺ and other. This revised version was published online in August 2006 with corrections to the Cover Date.     

Studies of Some New Aminocyclodiphosphazane Complexes of Co(II), Ni(II), and Cu(II)

The ligand aminocyclodiphosph(V)azane derivative (III) and its complexes with Co(II), Ni(II), and Cu(II) ions were prepared and characterized by microanalytical, FTIR, ¹H, ¹³C, and ³¹P-NMR, UV/Visible, thermogravimetric (TGA) analysis, and magnetic moments. The ligand acts in a tetrahedral manner forming 2:1 metal to ligand ratio. The copper complex is assigned to be tetrahedral while cobalt and nickel complexes were assigned to be octahedral structure.     

Structural, Spectroscopic, and Thermal Behaviour of Bis-(thiosaccharinate)-aqua-cadmium(II)

Summary.  The crystal structure of the title complex, [Cd(tsac)₂(H₂O)], has been determined by single crystal X-ray diffraction methods. It crystallizes in the monoclinic space group C2/c (a = 12.236(3), b = 8.919(3), c = 16.655(3) ?, β = 96.18(2)°, Z = 4). The molecular structure was solved from 1705 independent reflections with I > σ(I) and refined to R ₁ = 0.0489. Infrared and Raman spectra of the complex were recorded and are briefly discussed. Its thermal behaviour was investigated by thermogravimetry and differential thermal analysis. Received December 18, 2000. Accepted February 19, 2001     

Synthesis and characterization of oxazolone complexes with Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in different counterions

Oxazolone forms (1:1) complexes with Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ chlorides, as well as forms (1:1) complexes with Co²⁺ and Cu²⁺ acetates. All the complexes are found to be non-electrolytes in DMF; tetrahedral, square-planar and octahedral structures are assigned to them based on electronic and magnetic data. IR studies reveal that the complexes are formed by donating the lone-pair electron from O and N atoms to the metal ion. The thermal decomposition of the [ML·mX·nH₂O]_y·H₂O chelates was studied by TG–DTA techniques. The mechanism of the decomposition has been established from TG–DTA data. The kinetic parameters, activation energy (E_a) and pre-exponential factor (A), were calculated from TG curves using Coats and Redfern method. Relative thermal stabilities of the chelates have been evaluated on the basis of these parameters.     

Copper(II) Complexes of Spirohydantoins. Synthesis,Quantum-Chemical,and Spectroscopic Study

A series of new Cu(II) complexes with important physiologically active cycloalkane-5-spirohydantoines are synthesized reacting as a result of CuCl₂ · 2H₂O interaction with the ligands in alkaline water medium. Their structures were studied using spectroscopic (IR and EPR) methods. For comparison, ab initio calculations of the structure and IR spectra of the corresponding Cu(II) complexes were also performed. It was proven that with cyclopentane-5-spirohydantoins, distorted (flattened) tetrahedral structure is realized Cu(L_–H)₂(H₂O)₂, while with the higher cycloalkane-5-spirohydantoins linear Cu(II) complexes of the type CuL_–H(OH) are formed.     

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.