New cobalt(II) dithiocarbazates of the general formula [Co(IN-DtczH-Sal)2]Xn (IN-DtczH-Sal = salicylaldehyde Schiff base of isonicotinoyldithiocarbazic acid; X = Cl, Br, ClO4, NO3, CH3COO for n = 2, X = SO4, C2O4, CO3 for n = 1) have been prepared and investigated by elemental analyses, molar conductance measurements, infrared and electronic spectral and room temperature and variable temperature magnetic susceptibility measurements. All the complexes have NS linkage of the ligand. The magnetic

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... nd spectral studies suggest that the complexes, viz. [Co(IN-DtczH-Sal)2]X2 (X = Cl, CH3COO, NO3) are square planar, while the temperature dependent magnetic behaviour of the complexes [Co(IN-DtczH-Sal)2]Xn (X = Br, ClO4 when n = 2; X = SO4, C2O4 when n = 1) indicate square planar-tetrahedral equilibrium. Additionally the magnetic behaviour of the two complexes with sulphate and oxalate as the counter anions has also been attributed to the presence of intermolecular superexchange antiferromagnetic interactions in a suphato/oxalato bridged dimeric structure. The Co(IN-DtczH-Sal)2CO3 complex exhibits octahedral geometry, with carbonate anion also taking part in bonding. INTRODUCTION Sulphur-nitrogen chelating agents derived from Schiff bases of dithiocarbazic acids and their transition metal complexes have been the subject of many studies 1-5 mainly because of their interesting physico-chemical properties and potentially beneficial biological activities. The dithiocarbazate and its substituted derivatives have received much attention because (i) they provide an interesting series of ligands whose properties can be greatly modified by introducing different organic substituents, thereby causing a variation in the ultimate donor properties, (ii) the interaction of these donors with metal ions gives complexes of different donacity, geometry and hence physico-chemical properties, and (iii) these complexes are potentially biologically active. Schiff bases of dithiocarbazic acids with thiol groups have been reported to generally oxidize cobalt(II) to cobalt(III) 6,7. As part of our ongoing work on metal dithiocarbazates, we report here the magnetic and spectroscopic characterization of cobalt(II) complexes of the NS bonded bidentate Schiff base ligand formed by the condensation of salicylaldehyde with isonicotinoyldithiocarbazic acid. Oxidation of even trace amounts of cobalt(II) to cobalt(III) has been ruled out with the ligand of the present study.