The influence of steric effects on intramolecular secondary bonding interactions; cytotoxicity in gold(iii) bithiazole complexes

Abstract

The reaction of two sterically different bithiazole ligands with gold(III) was investigated. Our results show that, depending on the ligand used, different coordination geometries around the gold(III) center were achieved. Where sterically unhindered 4bt ligand was used, regular square-planar compound [Au(4bt)Cl₂][AuCl₄] (1) is isolated, while in the case of sterically hindered dm4bt ligand, the interplay between the steric effect and the intramolecular secondary bonding interaction leads to the formation of disordered square-pyramidal geometry in [Au(dm4bt)Cl₃] (2). Furthermore, the steric influence of the methyl group in the ligand plays an important role in the cytotoxicity of the compound in different cultures. Interestingly, compound 1 is more potent to kill a breast cancer cell line than cisplatin (13 times), and its cytotoxicity arises from the cationic part, [Au(4bt)Cl₂]⁺.