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Novel synthesis of palladium (II) complexes derived from 3-arylsydnone-4-carbaldehyde N(4)-phenylthiosemicarbazones and biological activity




The aim of this research is to investigate whether the oxygen atom O(6) in the sydnone ring of 3-arylsydnone-4-carbaldehyde N(4)-phenylthiosemicarbazones (HArSYTSCs, 3a–d) is a good electron donor atom upon metal complexation. Furthermore, ligands 3a–d and the corresponding palladium complexes (Pd(ArSYTSC)Cl, 4a–d) would be expected to find their potent biological activities.


The desired palladium complexes 4a–d were first synthesized from thiosemicarbazones 3a–d. Then, the antiproliferative activity of ligands 3a–d and complexes 4a-d were tested against human hepatocellular carcinoma and human cervical epithelioid carcinoma (HeLa) cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl trazolium bromide (MTT) assay.

Key findings

According to X-ray analyses, ligands 3a–d are bonded to the Pd (II) center in an O, N, S-tridentate coordination mode through sydnone carbonyl oxygen O(6), azomethine nitrogen and the thiolate sulfur atom. The carbonyl oxygen of the sydnone ring is found to be a good electron donor site upon metal complexation. Moreover, MTT assay results reveal that the palladium complexes 4a–d have greater antiproliferative activity than 5-fluorouracil. In particular, the complexes exhibit obvious better activity than the corresponding ligands 3a–d against HeLa cell.


The results indicate that the synthesized novel palladium complexes have greater antiproliferative activity than both 5-fluorouracil and the corresponding ligands against HeLa cell. Accordingly, the study of sydnonyl complexes bearing anticancer activities may support the development of coordination chemistry.