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.

Automated summary

Stable heteroleptic complexes were formed through reactions with common Pd(II) or Pt(II) complexes. The metal complexes of H2L Cy exhibit good inhibition towards bacteria and tumor cell lines.