CIS-DICHLORO-PALLADIUM(II) COMPLEXES WITH DIAMINOSUCCINIC ACID AND ITS DIETHYL ESTER - SYNTHESIS, MOLECULAR-STRUCTURE, AND PRELIMINARY DNA-BINDING AND ANTITUMOR STUDIES

The reactions of K2PdCl4 with meso-diaminosuccinic acid (H(2)dasa) in 0.1 M HCl or its diethyl ester dihydrochloride Et(2)dasa.2HCl in neutr alized aqueous solution yield cis-[Pd(H(2)dasa)Cl-2](I) and cis-[Pd(Et (2)dasa)Cl-2](II), respectively. These products were characterized by elemental analysis, IR spectroscopy, and TG-DTA thermal analysis. The crystal of II is monoclinic, space group C2/c ((a) under bar = 14.292( 5), (b) under bar = 14.636(5), (c) under bar = 13.435(5) Angstrom, bet a = 98.08(2)degrees, Z = 8, R = 0.041 and wR = 0.06). The Pd(II) atom exhibits a roughly square planar coordination with two Pd-N bonds (Et( 2)dasa) (2.014(2) and 2.049(7) Angstrom) and two cis-imposed Pd-Cl bon ds (2.294(2) and 2.303(2) Angstrom. Compound I reacts with 2,2'-bipyri dine in neutral aqueous solution to give [Pd(2,2'-bipy)(dasa)].3H(2)O( III) in a process of cis-chloride substitution by 2,2'-bipy as a model N-heterocyclic chelating entity. The molecular and crystal structure of III is also reported. It was observed that both cis-dichloro-Pd(II) complexes having Pd(H(2)dasa) (acidic) and Pd(Et(2)dasa)(esterified) chelate entities induce conformational changes in the covalent closed circular (ccc) form of pUC8 plasmid. Both compounds were assayed for a ntitumor activity in vitro against MDA-MB 468 and HL-60 human cancer c ell lines. The results show that compounds I and II have values of ID5 0 lower than those of K2PdCl4, and also lower than those of diaminoaci d ligands (meso-diaminosuccinic acid and meso-diaminosuccinate diethyl ester). Thus it is likely that the imposed cis-coordination of the ch elating H(2)dasa or Et(2)dasa to the Pd(II) center increases the biolo gical activity of these palladium(II) complexes.