Title
Red Emitting Cyclometallated Iridium(III) Complexes: Synthesis, Characterization and Evaluation of Biological Activities
Author
V. Thamilarasan, P. Karunakaran, N. Kavitha, C. Selvaraju, N. Sengottuvelan
Year
2016
Journal
Polyhedron
Abstract
A series of phosphorescent heteroleptic iridium(III) complexes containing two cyclometallating 6-chloro-2-(4-methoxyphenyl)-3-phenylquinoline (p-OMepq) ligands and one chromophoric ancillary ligand were synthesized and characterized: [(p-OMepq)2Ir(prz)] (1), [(p- OMepq)2Ir(biim)]Cl (2), [(p-OMepq)2Ir(bpy)]Cl (3) and [(p-OMepq)2Ir(dppe)]Cl (4) (where prz = pyrazine-2-carboxylic acid, biim = biimidazole, bpy = 2,2’-bipyridine, dppe = 1,2-bis(diphenylphosphino)ethane). The absorption, emission, lifetime measurements, cyclic voltammetry, molecular docking studies and thermal analysis of these complexes were systematically investigated. Binding of complexes 1-4with calf thymus DNA was investigated by UV-Vis, fluorescence, circular dichroic spectroscopy and viscosity measurements. The intrinsic binding constants Kb of complexes 1-4 with CT-DNA, obtained from UV-Vis absorption studies, were 2.3 × 104, 4.7 × 104, 4.3 × 104 and 5.0 × 104 M-1, respectively. The results indicated that the four complexes are able to bind to DNA with different binding affinities in the order 4 > 2 > 3 > 1. Complexes 1-4 exhibit a good binding propensity to bovine serum albumin (BSA) proteins, having relatively high binding constant values. A gelectrophoresis assay demonstrated that complexes 1-4 cannot promote the pBR322 plasmid DNA, plasmid pBluescript II KS+ DNA or pUC19 DNA cleavage in the presence of the reducing agent 3-mercaptopropionic acid. The cytotoxic activity of iridium(III) complexes 1-4 were tested with the human cervical cancer cell line (HeLa) and complex 4 was found to be more active compared to the other complexes.
Instrument
J-810
Keywords
Circular dichroism, DNA structure, Secondary structure, Ligand binding, Inorganic chemistry, Biochemistry