Indium(III)-terpyridine complexes: synthesis, structures and remarkable antifungal and anticancer activities

Abstract

Complexes of non-radioactive indium(III) with 2,2´;6´,2´´-terpyridine (tpy) ligands are rarely explored despite the popularity of tpy as a strong chelating ligand backbone. Herein, three mononuclear indium(III) complexes (In-1, In-2 and In-3) of tpy and its 4´-Cl and 4´-pyridyl derivatives have been synthesized and structurally characterized. While the crystal structure of In-1 has been previously studied, In-2 and In-3 were isolated and characterized for the first time. Two different polymorphs of In-2 were observed by simply varying the concentration of reactions. Molecules of In-3 were determined by X-ray crystallography to adopt the same mononuclear coordination mode as found in In-1 and In-2, while the remaining 4´-pyridyl ring was uncoordinated. Bioactivity studies revealed that indium(III) complexes In-1, In-2, and In-3 were fungicidal against the human fungal pathogen, Candida albicans, and several non-albicans Candida species. Moreover, the cytotoxicity studies showed these compounds were remarkably antiproliferative against human breast cancer cells (MCF-7 and MDA-MB 468).