Spectral and thermal studies on copper(II) complexes of acenaphthaquinonemono(4-methylquinolinyl) hydrazone

Cu(II) complexes of acenaphthaquinonemono(4-methylquinolinyl)hydrazone (AMH) of general composition [CuLX₂] (whereL=AMH;X=Cl, Br, I, OAc or NO₃) with the exception of sulphato complex, where the composition is found to be [CuLSO₄]₂ have been synthesized and characterized by elemental analyses, magnetic moment measurements, conductivity measurements, IR, electronic and EPR spectral techniques and by thermal analysis. A planar geometry is indicated for all the complexes. TG curves show one step decomposition of complexes and formation of CU₂O at the end of the step.One of the author (P.K.S.) is thankful to UGC, New Delhi (India), for providing financial assistance and is also indebted to the Department of Chemistry, University of Delhi, Delhi (India) for providing the necessary laboratory facilities.     

Spectral and thermal studies of 4-(1H-pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol complexes of cobalt(II), nickel(II) and copper(II)

4-(1H-Pyrazolo (3,4-d) pyrimidin-4-ylazo) benzene-1,3-diol was synthesized and characterized by various spectral and analytical techniques. Semiempirical quantum calculations using the AM1 method have been performed in order to evaluate the geometry and electronic structure of the title azodye in the ground state. The complex formation between Co(II), Ni(II) and Cu(II) ions and the title azodye was studied conductometrically and spectrophotometrically. The spectrophotometric determination of the title metal ions and titration using EDTA are reported. Co(II), Ni(II) and Cu(II) complexes of the title azodye have been synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility, IR, UV-Vis and thermal analysis (TGA and DTA).The spectral and magnetic data suggested the octahedral geometry for Co(II) and Ni(II) complexes while Cu(II) complexes have square planar geometry. The thermal studies confirmed the chemical formulations of the title complexes. The thermal degradation takes place in two or three steps depending on the type of the metal and the geometry of the complexes. The kinetics of the decomposition was examined by using Coats-Redfern relation. The activation energies and other activation parameters (DeltaH, DeltaS and DeltaG) were computed and related to the bonding and stereochemistry of the complexes.     

Spectral,magnetic, thermal and electrochemical studies on new copper(II) thiosemicarbazone complexes

The chelation behavior of some =N(1) and NH(4) thiosemicarbazones towards copper(II) ions has been investigated. The isolated complexes are characterized by elemental analysis, magnetic moment, electronic, IR, ESR and ms spectra, and by thermal and voltammetric measurements. The substituents on =N(1) and/or NH(4) thiosemicarbazones and the log K values of the ligands play an important role in complex formation. The IR spectra showed that the reagents HAT, HAET, HAPT, HApClPT, H₂ST and HBT are deprotonated in the complexes and act as mononegative SN donors; H₂SET, H₂SpClPT, H₂HyMBPT and H₂HyMBpClPT, as binegative NSO donors while H₂SPT is a mononegative NSO donor. The ESR spectra of the complexes are quite similar and exhibit axially symmetric g-tensor parameters with g _‖?>?g _⊥?>?2.0023. The loss of thiol and/or hydroxyl hydrogen was confirmed from potentiometric titrations of the ligands and their copper(II) complexes. The protonation constants of the ligands as well as the stability constants of their Cu(II) complexes were calculated. Thermogravimetric analysis of the complexes suggests different decomposition steps. The Coats–Redfern and Horowitz–Metzger equations have been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The redox properties, nature of the electroactive species and the stability of the complexes towards oxidation are strongly dependent on the substituents on the precursor NH(4) thiosemicarbazone. The redox data are discussed in terms of the kinetic parameters and the reaction mechanism.     

Spectral studies on copper(II) complexes of biologically active glutathione

Copper(II) complexes of reduced glutathione (GSH) of general composition Na[Cu(L)(X)]*nH2O (where LH2=GSH; X=Cl-, NO3-, NCS-, CH3CO2-, HCO2-, ClO4- and n=0-4) have been prepared and characterized by elemental analysis, magnetic susceptibility measurements, IR spectroscopy, EPR spectroscopy and ligand-field spectroscopy. The EPR and ligand field spectra in the solid state suggest planar geometry for all the complexes.     

Spectral and biological studies of copper(II) complexes of 2-acetyl-pyridine thiosemicarbazones with bulky 4N-substituents

Summary Copper(II) complexes of a large number of 2-acetylpyridine ⁴N-alkyl thiosemicarbazones were prepared and characterized. I.r., electronic and e.s.r. spectra of the complexes, as well as ¹H and ¹³C n.m.r. spectra of the thiosemicarbazones, were obtained. Both the thiosemicarbazones and their complexes show either modest or no growth inhibitory activity against Aspergillus niger, but many have considerable activity against Paecilomyces variotii. There is a relationship between the antifungal activity and size of the ⁴N-substituent for both the thiosemicarbazones and their copper(II) complexes.     

Spectral studies on cobalt(II), nickel(II) and copper(II) complexes of naphthaldehyde substituted aroylhydrazones

A series of new coordination complexes of cobalt(II), nickel(II) and copper(II) with two new aroylhydrazones, 2-hydroxy-1-naphthaldehyde isonicotinoylhydrazone (H(2)L(1)) and 2-hydroxy-1-naphthaldehyde-2-thenoyl-hydrazone (H(2)L(2)) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibility measurements, (1)H NMR spectroscopy, IR spectroscopy, electronic spectroscopy, EPR spectroscopy and thermal analysis. IR spectra suggests ligands acts as a tridentate dibasic donor coordinating through the deprotonated naphtholic oxygen atom, azomethine nitrogen atom and enolic oxygen atom. EPR and ligand field spectra suggests octahedral geometry for Co(II) and Ni(II) complexes and a square planar geometry for Cu(II) complexes.     

Spectral and structural studies of cobalt(II,III), nickel(II), and copper(II) complexes of dehydroacetic acid N4-dialkyl- and 3-azacyclothiosemicarbazones

Co^II,III, Ni^II, and Cu^II complexes of new dehydroacetic acid N4-substituted thiosemicarbazones have been studied. The substituted thiosemicarbazones, N4-dimethyl-(DA4DM), N4-diethyl-(DA4DE), 3-piperidyl-(DApip) and 3-hexamethyleneiminyl-(DAhexim), when reacted with the metal chlorides, produced two Co^II complexes, [Co(DA4DE)Cl₂] and [Co(DAhexim)₂Cl₂]; two Co^III complexes, [Co(DA4DM-H)₂Cl] and [Co(DApip-H)(DApip-2H)]; a paramagnetic Ni^II complex, [Ni(DAhexim)(DAhexim-H)Cl]; three diamagnetic Ni^II complexes, [Ni(DA4DM-H)Cl], [Ni(DA4DE-H)Cl] and [Ni(DApip-H)Cl]; and four Cu^II complexes with the analogous stoichiometry of the latter three Ni^II complexes. These new thiosemicarbazones have been characterized by their melting points, as well as i.r., electronic and ¹H-n.m.r. spectra. The metal complexes have been characterized by i.r. and electronic spectra, and when possible, n.m.r. and e.s.r. spectra, as well as elemental analyses, molar conductivities, and magnetic susceptibilities. The crystal and molecular structure of the four-coordinate Cu^II complex, [Cu(DAhexim-H)Cl] has been determined by single crystal X-ray diffraction and the anionic ligand coordinates via an oxygen of the dehydroacetic acid and the thiosemicarbazone moiety's imine nitrogen and thione sulfur.     

Spectral and thermal studies of solid-phase thermochromism of Co(II) double metal complexes

Tetrahedral solid state structures of the blue potassium tris(aryloxo)cobaltate(II)-tetrahydrofurane complexes of the formula KCo(OAr)(3).2thf (OAr = o-chloro-, o-bromo-, m-chloro-, p-bromo, 2,6-dichloro-, 2,4-dichloro- or 2,4-dimethylphenoxide) undergo solid-phase thermal tetrahedral to octahedral transformation accompanied by change in their colours from blue to rose (one-step thermochromism). Magnetic moments, electronic and infrared spectral studies supported these results. Thermal treatment of theses complexes leads to the loss of the crystallized thf molecule yielding also blue tetrahedral complexes. However, further heating leads to the loss of the coordinated thf molecule and the formation of rose octahedral trimeric products. TG-DTA results showed that the, two solvated thf molecules were eliminated in two steps. Mass spectral studies and IR intensity measurements confirmed the trimeric behaviour of the rose octahedral geometry of thermal products. Conductance measurements of solutions of these complexes in thf indicated that they behave as non-electrolytes.     

Spectral and thermal studies of new Co(II) and Ni(II) hexaaza and octaaza macrocyclic complexes

The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized and characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or 2,3-butanedionedihydrazone with the appropriate aldehydes in NH₄OH solution in the presence of the metal ions, Co(II) and Ni(II). The complexes were characterized by spectroscopic methods (IR, UV-Vis and ESR) and magnetic measurements as well as thermal analysis (TG and DTA). The results obtained are commensurate with the proposed formulae. Spectral studies indicate that these complexes have an octahedral structure. From conductivity measurements the complexes are non-electrolytes. The kinetic of the thermal decomposition of the complexes was studied and the thermodynamic parameters are reported.     

Spectral,magnetic studies and molecular orbital calculations for (4,5-dimethyl-3-pyrazolyl)aldazine copper(II) complexes

Summary A new series of copper(II) complexes derived from (4,5-dimethyl-3-pyrazolyl) aldazine (DMPA), formulated as: (a) [LCuX₂]·nEtOH; (b) [LCu(H₂O)](ClO₄)₂; and (c) [LCuX]BF₄·nH₂O, where n = 1/2 or 1, X = Cl or Br and L = DMPA, have been synthesized. The formulations are based on elemental analyses and molar conductivity data. I.r., u.v.-vis., e.s.r. and magnetic data reveal that the complexes are trigonal bipyramidal, tetrahedral and stacked square-planar structures for (a), (b) and (c), respectively. The trigonal bipyramidal structure for class (a) compounds is confirmed using the atom superposition and electron delocalization-molecular orbital calculations, which agree with the experimental electronic spectral data. Variable temperature magnetic susceptibility data shows a ferromagnetic interaction within copper(II) complexes of class (c).     

Spectral, thermal, electrochemical and analytical studies on Cd(II) and Hg(II) thiosemicarbazone complexes

The coordination characteristic of the investigated thiosemicarbazones towards hazard pollutants, Cd(II) and Hg(II), becomes the first goal. Their complexes have been studied by microanalysis, thermal, electrochemical and spectral (electronic, IR and MS) studies. The substitutent (salicylaldehyde, acetophenone, benzophenone, o-hydroxy-p-methoxybenzophenone or diacetylmonoxime) plays an important role in the complex formation. The coordination sites were the S for thiosemicarbazide (HTS); NN for benzophenone thiosemicarbazone (HBTS); NS for acetophenone thiosemicarbazone (HATS) and salicylaldehyde thiosemicarbazone (H(2)STS); NNS or NSO for diacetylmonoxime thiosemicarbazone (H(2)DMTS). The stability constants of Hg(II) complexes were higher than Cd(II). The kinetic and thermodynamic parameters for the different thermal decomposition steps in the complexes have been evaluated. The activation energy values of the first step ordered the complexes as: [Cd(H(2)STS)Cl(2)]H(2)O>[Cd(H(2)DAMTS)Cl(2)]>[Cd(HBTS)(2)Cl(2)]2H(2)O>[Cd(HATS)(2)Cl(2)]. The CV of [Cd(H(2)STS)Cl(2)]H(2)O and [Hg(HBTS)Cl(2)] were recorded. The use of H(2)DMTS as a new reagent for the separation and determination of Cd(II) ions from water and some synthetic samples using flotation technique is aimed to be discussed.     

Cobalt(II), nickel(II) and copper(II) complexes of 4-(sulfonylazido)phenylazopyrazolones

Transition metal complexes of Co^II, Ni^II and Cu^II with 4-(4-azidosulfophenylazo)-5-phenyl-3,4-dihydro-2H-pyrazol-3-oneHL¹, 4-(4-azidosulfophenylazo)-5-methyl-2-phenyl-3,4-dihydro-2H-pyrazol-3-one HL² and 4-(3-azidosulfo-6-methoxyphenylazo)-5-methyl-2-phenyl-3,4-dihydro-2H-pyrazol-3-one HL³ were prepared and characterized by elemental analyses, molar conductances and magnetic susceptibilities and by i.r., electronic and e.s.r. spectral measurements as well as thermal (d.t.a and t.g.a.) analysis. The i.r. spectra indicate that HL acts as a bidentate ligand coordinating via the azo and enolic-oxygen linkages. The electronic spectral data and magnetic moments suggest a tetragonally distorted octahedral geometry for the complexes having the formula ML₂·2H₂O, (M = Co^II, Ni^II and Cu^II), square pyramidal geometry for CuL ₂ ³ H₂O and tetrahedral geometry for CoL ₂ ³ . The X-band e.s.r. spectra of the copper(II) complexes reveal anaxial symmetry for both CuL ₂ ² 2H₂O and CuL ₂ ³ H₂O while CuL ₂ ¹ O is isotropic in the solid state at room temperature. The d.t.a. curves show two exothermic peaks for all three complexes CoL ₂ ³ ,NiL ₂ ³ 2H₂O and CuL ₂ ³ H₂O and one endothermic peak for the latter two aqua complexes.     

Spectral and structural studies of nickel(II) complexes of salicylaldehyde 3-azacyclothiosemicarbazones

Mononuclear nickel(II) complexes with two ONS donor thiosemicarbazone ligands {salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone [H₂L¹] and salicylaldehyde 3-tetramethyleneiminyl thiosemicarbazone [H₂L²]} have been prepared and physico-chemically characterized. IR and electronic spectra of the complexes have been obtained. The thiosemicarbazones bind to the metal as dianionic ONS donor ligands in all the complexes except in [Ni(HL¹)₂] (1). In compound 1, the ligand is coordinated as a monoanionic (HL⁻) one. The magnetic susceptibility measurements indicate that all the complexes are mononuclear and are diamagnetic. The complexes were given the formulae [Ni(HL¹)₂] (1), [NiL¹py] (2), [NiL¹α-pic] (3), [NiL¹γ-pic] · H₂O (4), [NiL²py] (5) and [NiL²γ-pic] (6). The structures of compounds 2 and 3 have been solved by single crystal X-ray crystallography and were found to be distorted square planar in geometry with coordination of azomethine nitrogen, thiolato sulfur, phenolato oxygen and pyridyl nitrogen atoms.     

Synthesis,electrochemistry and thermal studies of fluoro and imidazole complexes of copper(II)

Complexes of the (H2Im)4[CuF6], (H2Im)2[CuF4(H2O)2] type (H2Im=imidazolium cation) and Cu(HIm)4X2 (X=Cl or Br; HIm=imidazole) have been prepared in aqueous solution by the interaction of CuO·nH2O with the respective halide in the presence of imidazole. Formation of a particular complex species has been shown to be dependent on the reaction solution pH and also on the nature of the halide. The complexes were characterised on the basis of FT-i.r., u.v.–vis. and e.s.r. spectroscopy and by measurement of magnetic susceptibilities and solution electrical conductivities. Cyclic voltammetry revealed a two-peak quasi-reversible response for [Cu(HIm)4Br2], while other complexes produced overall irreversible voltammographs. Thermal decomposition profiles are consistent with the proposed formulations.     

Thermal studies of cobalt(II), nickel(II) and copper(II) 3-substituted-4-salicylideneamino-5-mercapto-1,2,4-triazole complexes

Complexes of Co^II, Ni^II and Cu^II with 3-substituted-4-salicylideneamino-5-mercapto-1,2,4-triazole have been prepared and characterized by elemental analysis, electronic, i.r., e.s.r. and t.g. studies. T.g. studies show that the complexes thermally degrade in two steps. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The activation energies of both the thermal degradation steps lie in the 0.24–42.67 kJ mol⁻¹ range. This revised version was published online in June 2006 with corrections to the Cover Date.     

Spectral,thermal and biological activity studies on ruthenium(II) complexes with some pyridylamines

Complexes resulted from the interaction of [Ph₃P]₃RuCl₂ with 2-aminoethylpyridine (aepy), 2-hydrazinopyridine (hzpy) and dipicolylamine (dpa) with KPF₆ have been isolated from ethanol. The structures of the complexes were investigated using elemental analyses, IR, magnetic moment, UV-Vis and ¹H NMR spectroscopy. The complexes have been isolated as [Ru(hzpy)₃](PF₆)₂, [Ru(hzpy)₂(aepy)](PF₆)₂, [Ru(hzpy)(aepy)₂](PF₆)₂, [Ru(dpa)₂](PF₆)₂ in an octahedral geometry. The thermal decomposition of complexes was discussed in terms of their structures and the thermodynamic parameters were evaluated. The metal complexes were screened for their antibacterial activity against bacterial species, Escherichia coli, Staphylococcus aureus, as well as fungus (Candida). The activity data show the metal complexes have potent antibacterials against one ore more bacterial species.