Synthesis, characterization, antiplasmodial evaluation and electrochemical studies of water-soluble heterobimetallic ferrocenyl complexes

Three new ferrocenyl-containing heterobimetallic complexes were synthesized using a sodium sulfonate-salicylaldimine mononuclear ferrocenyl complex and various metal precursors. Complexation with ruthenium(II), rhodium(III) and iridium(III) precursors yielded the heterobimetallic complexes, which display good water-solubility. The ferrocenyl ligand acts as a N,O-bidentate chelating ligand, coordinating to the metal center via the imine nitrogen and the deprotonated phenolic oxygen. The complexes were characterized using analytical and spectroscopic techniques. The compounds were evaluated for in vitro antiplasmodial activity against the NF54 chloroquine-sensitive strain of Plasmodium falciparum. The mono- and bimetallic complexes exhibit enhanced activity compared to the salicylaldimine hydrazone. The compounds were evaluated for their ability to inhibit β-haematin formation but were inactive, suggesting an alternative reason for their antiplasmodial activity. Electrochemical studies on the bimetallic complexes revealed a voltammetric wave corresponding to the oxidation of the ferrocenyl group and another at a more positive potential which inhibited the reversibility of the ferrocenyl oxidation.