2,6-DIACETYLPYRIDINE BIS(THIOSEMICARBAZONES) ZINC-COMPLEXES - SYNTHESIS, STRUCTURE, AND BIOLOGICAL-ACTIVITY

The reaction of zinc chloride, acetate, or perchlorate with two bis(thiosemicarbazones) of 2,6-diacetylpyridine [H(2)daptsc = 2,6-diacetylpyridine bis(thiosemicarbazone) and H(2)dapipt = 2,6-diacetylpyridine bis(hydrazinopyruvoylthiosemicarbazone)] leads to the formation of four novel complexes that have been characterized by spectroscopic studies (NMR, IR) and biological properties. The crystal structures of the two compounds-[Zn(daptsc)](2) . 2DMF (1) and [Zn(H(2)dapipt)(OH2)(2)](ClO4)(2) . 3H(2)O (2)-also have been determined by x-ray methods from diffractometer data. Compound (1) is dimeric and the two zinc atoms have a distorted octahedral coordination. The ligand is deprotonated. In compound (2), the coordination geometry about zinc is pentagonal-bipyramidal and the ligand is in the neutral form. The molecular structure of (2) consists of cations [Zn(H(2)dapipt)(OH2)(2)](2+), ClO4- disordered anions, and three water molecules of solvation. Biological studies have shown that the ligands and the complexes Zn(daptsc). 1/2EtOH and Zn(H(2)daptsc)Cl-2 have an effect in vitro on cell proliferation and differentiation (inhibition); both are concentration dependent. [Zn(daptsc)](2) . 2DMF (1) shows the effects at lower concentration values with respect to other compounds.