The influence of steric effects on intramolecular secondary bonding interactions; cytotoxicity in gold(iii) bithiazole complexesCCDC 840560 and 840561. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c3dt00073g

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)Cl 2 ][AuCl 4 ] ( 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)Cl 3 ] ( 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)Cl 2 ] + . The reaction of two sterically different bithiazole ligands with Au( iii ) was investigated. In the case of these ligands two different geometry were obtained. Compound 1 is more potent to kill a breast cancer cell line than cisplatin (13 times).