EPR, cyclic voltammetric and biological activities of copper(II) complexesof salicylaldehyde N(4)-substituted thiosemicarbazone and heterocyclic bases

An interesting series of heterocyclic base adducts of copper(II) complexes have been synthesised by the reaction of copper(II) acetate with salicylald ehyde N(4)-phenylthiosemicarbazone in presence of heterocyclic bases like p yridine (py), piperidine (pip), beta/gamma-picoline (beta/gamma-pic), 1,10- phenanthroline (phen) and 2,2'-bipyridine (bipy). IR, electronic, H-1 and C -13. NMR spectra of the thiosemicarbazone, as well as IR. electronic and EP R spectra of the complexes have been obtained. Based on EPR studies spin Ha miltonian and bonding parameters have been calculated. The g values, calcul ated for all the complexes in frozen DMF, indicate the presence of the unpa ired electron in the d(x)(2)-y(2) orbital. The metal-ligand bonding paramet ers evaluated showed strong in-plane sigma and in-plane pi bonding. The mag netic and spectroscopic data indicate a square planar geometry for the four -coordinate and a distorted square pyramidal for five-coordinate complexes. From cyclic voltammetric data reversible copper(II)/copper(I) couples are observed for these complexes. The thiosemicarbazone and its copper(II) comp lexes show growth inhibitory activity against human pathogenic bacteria Sal monella typhi, Shigella dysentariae, non-coagulace Staphylococcus, Photobac terium sp. and Staphylococcus aureus and plant pathogenic fungi Rhizoctonia , Collectotrichium and Aspergillus sp. (C) 1998 Elsevier Science Ltd. All r ights reserved.