Transition-metal complexes of isatin-beta-thiosemicarbazone. X-ray crystalstructure of two nickel complexes

Manganese, iron, cobalt, nickel, copper and zinc complexes of isatin-beta-t hiosemicarbazone (H2L) have been synthesized and spectroscopically characte rized. The X-ray crystal structures of two nickel complexes, namely [Ni(HL) (2)] . EtOH (1) and [Ni(HL)(2)] . 2DMF (2), reveal a distorted octahedral c oordination with the monodeprotonated ligand that behaves as an O,N,S terde ntate. Different packing interactions are determined by the presence of dif ferent crystallization solvents, i.e. ethanol in 1 and dimethylformamide (D MF) in 2. H-1 and C-13 NMR studies of the ligand and zinc complexes in solu tion were carried out and a complete assignment for the ligand was made by homodecoupling, gradient assisted 2D H-1-C-13 HMQC and HMBC NMR spectroscop y. Biological studies, carried out in vitro on human leukaemic cell lines U 937, have shown that the free ligand and the copper(II) complex are more ac tive in the inhibition of cell proliferation than the nickel complexes. No compound was able to induce apoptosis. (C) 1999 Elsevier Science Inc. All r ights reserved.