Synthesis, characterization and antiplasmodial evaluation of cyclopalladated thiosemicarbazone complexes

Cyclopalladated thiosemicarbazone complexes arising through chelation of the tridentate thiosemicarbazone ligand via the ortho-carbon of the aryl ring, the imine nitrogen and the thiolate sulfur were synthesized with the phosphorus ligand occupying the fourth coordination site of the palladium(II) ion. These complexes were prepared by cleavage of the bridging Pd–S bonds of previously reported tetranuclear complexes with phosphorus ligands such as PTA and aminophosphines. The cyclopalladated complexes along with their free ligands were screened for antiplasmodial activity against two Plasmodium falciparum strains, NF54 (chloroquine-sensitive) and Dd2 (chloroquine-resistant), exhibiting inhibitory effects in the low micromolar range.