Synthesis, characterization and antiplasmodial evaluation of cyclopalladated thiosemicarbazone complexes

•Tridentate cyclopalladated thiosemicarbazone complexes have been prepared.•Various phosphorus ligands occupy the fourth coordination site.•The antiplasmodial activity of the cyclopalladated complexes was evaluated.•The complexes displayed inhibitory effects in the low micromolar range.

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.

Graphical abstractCyclopalladated thiosemicarbazone complexes containing phosphine and diphosphine ligands were synthesized through cleavage of the bridging Pd–S bonds of precursor tetranuclear palladium complexes. The cyclopalladated complexes were evaluated for their antiplasmodial activity and showed moderate inhibitory effects in the low micromolar range against chloroquine-sensitive (NF54) and chloroquine-resistant (Dd2) Plasmodium falciparum strains.Figure optionsDownload full-size imageDownload as PowerPoint slide