Synthesis, Structure, DNA/Protein Binding, and Anticancer Activity of Some Half-Sandwich Cyclometalated Rh(III) and Ir(III) Complexes

Abstract

The Schiff base ligands benzylidene(4-tert-butylphenyl)amine 4-methyl ester (L1), (4-nitrobenzylidene)(4-tert-butylphenyl)amine (L2), and (4-cyanobenzylidene)(4-tert-butylphenyl)amine (L3) and the new series of cyclometalated mononuclear piano-stool complexes [(η5-C5Me5)RhCl(L1)] (1), [(η5-C5Me5)RhCl(L2)] (2), [(η5-C5Me5)RhCl(L3)] (3), [(η5-C5Me5)IrCl(L1)] (4), [(η5-C5Me5)IrCl(L2)] (5), and [(η5-C5Me5)IrCl(L3)] (6) have been synthesized. The ligands L1–L3 and complexes 1–6 have been thoroughly characterized by satisfactory elemental analyses, spectral studies (ESI-MS, IR, 1H and 13C NMR, UV–vis), and structures of 1–3 authenticated by X-ray single-crystal analyses. Efficient binding of 1–6 with calf thymus DNA (CT DNA) have been established by UV–vis and emission spectroscopic studies. Protein binding (bovine serum albumin, BSA) has been investigated by UV–vis, fluorescence, synchronous, and 3D fluorescence spectroscopy. Binding of the complexes with DNA through minor groove and hydrophobic interaction wi...