THERMAL, SPECTRAL, ESR AND MAGNETIC STUDIES OF SOME COPPER(II) THIOSEMICARBAZONE COMPLEXES

Copper(II) forms 1:1 dimeric complexes with the thiosemicarbazones of salicylaldehyde, 5-bromo-salicylaldehyde, 2-hydroxy-1-naphthaldehyde and vanillin. All the complexes are found to be non-electrolytes in nitrobenzene and square planar structures are assigned to them based on electronic, ESR and room-temperature magnetic measurements. IR studies reveal that the complexes are formed by the replacement of the hydrogen atom of the SH group by CuII with N and S coordinating to the metal. Thermal studies indicate that the decomposition takes place in two stages. Interpretation and mathematical analysis of these data and evaluation of the order of reaction, and of the energy and entropy of activation, based on Coats-Redfern, Horowitz-Metzger and MacCallum-Tanner methods, are also given. On the basis of our findings the relative thermal stabilities of the CuII chelates can be given as [Cu(VTSC)Cl]2 < [Cu(NTSC)Cl]2 = [Cu(BrSTSC)Cl]2, < [Cu(STSC)Cl]2. © 1990.