Cationic Ru(II), Rh(III) and Ir(III) complexes containing cyclic π-perimeter and 2-aminophenyl benzimidazole ligands: Synthesis, molecular structure, DNA and protein binding, cytotoxicity and anticancer activity

Abstract

Synthesis, characterization, DNA and protein binding as well as anticancer activity of the organometallic complexes [(η6-C6H6)RuCl(APBI)]Cl (1), [(η6-p-MeC6H4Pri)RuCl(APBI)]Cl (2), [(η6-C6Me6)RuCl(APBI)]Cl (3), [(η5-C5Me5)RhCl(APBI)]Cl·H2O (4) and [(η5-C5Me5)IrCl(APBI)]Cl·H2O (5) containing 2-aminophenyl benzimidazole (APBI) have been described. The complexes 1–5 exhibited strong DNA, protein binding and anticancer activity against cervical cancer (SiHa) cell line. Their binding with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) have been examined by absorption and emission spectral studies. Strong interactions between complexes and CT-DNA have been affirmed by absorption spectral and EthBr displacement studies, while interaction with BSA via static quenching explored by fluorescence titration, synchronous and 3D fluorescence spectroscopy. The interactions between 1–5 and DNA has also been scrutinized by 1H NMR spectral studies using guanosine as a model for DNA. These results have been supported by DFT calculations and molecular docking studies. Cytotoxicity, apoptosis and in vitro anticancer activity of 1–5 toward SiHa cell line have been investigated by MTT assay and acridine (AO)/ethidium bromide (EthBr) fluorescence staining. Overall results revealed that DNA and protein binding, as well as anticancer activity of 1–5 follows the order as 5 > 3 > 2 > 1 > 4.