Syntheses, Structures, and Biological Activities of Pd(II) and Pt(II) Complexes with some 1-picolinoyl-4-substituted Thiosemicarbazides

Reactions of three 1-picolinoyl-4-substituted thiosemicarbazides H 2 L , namely H 2 L Et , H 2 L Cy , and H 2 L Ph , with equimolar amounts of common Pd(II) or Pt(II) complexes [M(PPh 3 ) 2 Cl 2 ] (M = Pd, Pt) bring about the formation of stable heteroleptic complexes with the compositions [M( L )(PPh 3 )] (M = Pd, Pt). Their molecular structures show mononuclear square planar complexes in which the acyl thiosemicarbazides are doubly deprotonated and serve as tridentate ligands bonded to the metal ion center via ( N pyridine , N 1 , S ) donor sets. The organic ligands H 2 L Et and H 2 L Ph as well as all of their metal complexes show only weak inhibitory effects on microbial strains examined, whereas the metal complexes of H 2 L Cy exhibit good inhibition towards B. subtilis and L. fermentum with MIC values lower than those of ampicillin. Furthermore, the in vitro cytotoxicity of H 2 L and the complexes were tested against cancerous cell lines MCF7 and HepG2. The organic ligands exhibit moderate antiproliferative effects with the increasing order of activity H 2 L Et < H 2 L Cy < H 2 L Ph for both cell lines. Surprisingly, except for the Pt(II) complex of H 2 L Cy , the other metal complexes are highly toxic with IC 50 in the range of 4.22 +/- 0.37 - 16.0 +/- 1.05 mu M for HepG2 and 3.26 +/- 0.41 - 20.6 +/- 2.12 mu M for MCF7. Most IC 50 values of the metal-based compounds are comparable with those of cisplatin under the same condition.