Yudhvir K. Bhoon

Spectroscopic studies on copper(II) complexes derived from a substituted 2-acetylpyridine thiosemicarbazone

SummaryCopper(II) complexes of general formula [Cu(L4A)X] (where L4A is the deprotonated ligand, 1 H-hexahydroazepine-1-thiocarboxylic acid-2-[1-(2-pyridinyl)ethylidene]hydrazide and X=Cl, Br, I, NCS, NO3 and OAc) and [Cu(HL4A)(L4A)]ClO4 have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, i.r. spectra, electronic spectra, conductivity measurements and e.s.r. spectra in the polycrystalline state and in chloroform solution. For all complexes, except the perchlorate salt, coordination occurs via imine nitrogen, pyridine nitrogen and thione sulphur. For the perchlorate salt, L4A is tridentate, while HL4A is monodentate via imine nitrogen. Electronic spectra suggest planar geometry for all the complexes. The calculated e.s.r parameters suggest coordination through sulphur in agreement with the i.r. results.

Spectral studies of iron(III) complexes of substituted thiosemicarbazones of 2-acetylpyridine

SummaryIron(III) complexes of four substituted thiosemicarbazones of 2-acetylpyridine of general. formula [FeL2]ClO4 (where L is a deprotonated ligand) have been synthesised and characterised by elemental analyses, magnetic susceptibility measurements in the polycrystalline state at room temperature, i.r. spectra, electronic spectra and e.s.r. spectra recorded in polycrystalline state, in methanol solution at room temperature and at 77 K. All the complexes are 1:1 electrolytes. The ligands coordinate via the pyridine nitrogen, imine nitrogen and thione sulphur. E.s.r. spectra and with magnetic studies suggest a spin-paired configuration for the iron(III) complexes.

Characterization of copper(II) complexes of N4, N4-disubstituted thiosemicarbazones of 2-acetylpyridine by combined evaluation of electronic and ESR parameters

Abstract Copper(II) complexes of 2-acetylpyridine 4,4-dimethyl-3-thiosemicarbazone (L′H) and 2-acetylpyridine 4-(4-methylpiperidinyl)-3-thiosemicarbazone (LH) of the general formula CuLX (where L is a deprotonated ligand and X = F−, Cl−, Br−, I−, OAc− and NO−3) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements between 93 and 298 K in the polycrystalline state, i.r. spectra, electronic spectra, conductivity measurements and ESR spectra recorded in the polycrystalline state, in chloroform and dimethylformamide solution at room temperature and at 77K. The molar conductivities measured in dimethylformamide for all complexes show them to be non-electrolytes. The terdentate character of the ligands in all the complexes is inferred from i.r. spectral studies. The i.r. spectra also confirm the monodentate nature of the polyatomic anions such as nitrate and acetate. The electronic spectra in Nujol mulls, chloroform or dimethylformamide solution suggest planar geometry for all of the complexes. The calculated ESR parameters show an axial dx2−y2 ground state and suggest coordination through sulphur in agreement with the i.r. results. Little change in the value of g with temperature indicates no significant change in planarity of these four coordinated species. ESR spectra in solution at room temperature and 77 K also suggest a strong covalent environment with strong in-plane sigma and pi bonds provided by the ligands.

Manganese(II) complexes of substituted thio- and seleno- semicarbazones of 2-acetylpyridine: E.s.r., magnetic and electronic spectral studies

SummaryManganese(II) bis(ligand) complexes of substituted thiosemicarbazones and selenosemicarbazones derived from 2-acetylpyridine of general formula [MnL2] (where L=deprotonated ligand) have been synthesized and characterised by elemental analyses, electronic spectra in solution, i.r. spectra, magnetic measurements and e.s.r. spectra recorded in polycrystalline state and in solution at room temperature and 77K. The terdentate character of the ligands in all the complexes is inferred from i.r. spectra. The electronic spectra along with e.s.r. spectra suggest an octahedral environment around the manganese(II). The metal-ligand bonds are moderately covalent. Thus all the complexes reported here are six-coordinated and high-spin octahedral.

Characterisation of nickel(II) complexes of a substituted 2-acetylpyridine thiosemicarbazone by electronic and n.m.r. spectral studies

SummaryNiII complexes of 1H-hexahydroazepine-1-thiocarboxylic acid-2-[1-(2-pyridinyl)ethylidene] hydrazide (HL4A) of general formula [Ni(L4A)X] (X=Cl, Br, I or NCS) have been synthesized and characterised by physical and spectroscopic methods. The molar conductivities show that all of the complexes are non-electrolytes. The terdentate character of the ligand in all cases is inferred from i.r. spectra, while the electronic spectra suggest planar geometries.

Magnetic and EPR properties of Mn(II), Fe(III), Ni(II) and Cu(II) complexes of thiosemicarbazone of α-hydroxy-β-napthaldehyde

Abstract Mn(II), Fe(III), Ni(II) and Cu(II) complexes of the thiosemicarbazones of α-hydroxy-β-naphthaldehyde have been isolated. Ni(II) complex is diamagnetic, Cu(II) is planar involving metal-metal interactions, Mn(II) complex (μ eff = 3.86B.M) has been assigned a planar structure with S = 3/2 while Fe(III) complex is five coordinated with S = 3/2.

Intermediate spin iron(III) complexes of N4,N4-disubtituted 2-acetylpyridine thiosemicarbazone

SummaryMagnetic susceptibility and Mössbauer spectroscopy measurements have been carried out on [FeIII(SAm)Cl2], and indicate an intermediate spin state for the ferric ion. The temperature-independent magnetic moment of (4.17±0.05) μB, the quadrupole splitting=4.09 mm s−1 and isomer shift=0.133 mm s−1 are in agreement with such formulation. These studies, together with infrared data, are used to suggest a possible structure of the complex.

Spectral magnetic EPR studies of copper(II) complexes of N-phenyl-2-[1-(2-pyridinyl)ethylidene]hydrazinecarbothioamide

Abstract Copper(II) complexes of N -phenyl-2-[1-(2-pyridinyl)ethylidene]hydrazinecarbothioamide (LH) of general composition [L − Cu(II)X − ] (where X − = F − , Cl − , Br − , I − , OAc − NO − 3 and NCS − ) have been synthesized and characterized by elemental analysis, magnetic measurements, i.r. spectra, electronic spectra, EPR spectra and conductivity measurements. The EPR spectra of the complexes were recorded in the polycrystalline state, in dimethylformamide solution at room temperature and at − 195°C, whereas electronic spectra were recorded in dimethylformamide and Nujol. Various bonding parameters were calculated. A planar geometry is indicated for the complexes.

Iron(III) complexes of 2-acetylpyridine-4-phenyl-3-thiosemicarbazones: Magnetic, E.s.r. and spectral studies

SummaryIron(III) complexes of 2-acetylpyridine-4-phenyl-3-thiosemicarbazone (LH) with the general formulae FeLX2 (X = Cl, Br, NO3 or SCN) and FeLSO4 have been prepared and characterised by elemental analysis and by magnetic measurements in the polycrystalline state in the 77–298 K range and by electronic, i.r. and e.s.r. spectra. The FeLX2 species (X = Cl, NCS or NO3) are square pyramidal of intermediate spin-state (S=3/2) with an4A2 ground state. The magnetic behaviour of FeLSO4 is commensurate with high order effects coupled with antiferromagnetic exchange interactions. FeLBr2 is a spin-free dimer involving bromine bridging between two FeLBr2 square pyramids. However, the low-spin species [FeL(DMF)3]2+ exists in dimethylformamide solution.

Synthesis and Characterization of Iron(III) Complexes of a Substituted 2-Acetyi, Pyridine Thiosemicarbazone

Abstract Iron(III) bis(ligand) complexes of a substituted thiosemicarbazone of 2-acetylpyridine have been prepared and charactmized by physico-chemical and spectroscopic methods. The complex prepared from ferric chloride was found to be a 1:1 electrolyte whereas others are non-electrolytes. The ligand deprotonates and coordinates via the pyridine nitrogen, imine nitrogen, and thiolate sulfur. The neutral ligand coordinates through imine and pyridine nitrogens only. The complex prepared from ferric chloride has an ion pair geometry involving a low-spin iron(III) cation antl high spin iron(III) anion. The EPR studies indicate a high-spin low-spin equilibrium for the nitrato complex. All other complexes are low spin.