Cyclometalated iridium(III) complex of 6-hydroxydipyrido[3,2-a:2′,3′-c]phenazine: synthesis, and acid-base and avid DNA binding properties

A new cyclometalated Ir(III) complex [Ir(ppy)(2)(hdppz)]PF6 (Hppy = 2-phenylpyridine and hdppz = 6-hydroxydipyrido[3,2-a:2',3'-c]phenazine) was synthesized and characterized. The pH effects on the UV vis absorption spectra were studied and ground-state acid ionization constant pK(a) values of the complex were derived. The calf thymus DNA (ct-DNA) binding properties of the complex were investigated with UV-vis absorption spectrophotometric titrations, DNA competitive binding with ethidium bromide, DNA melting experiments, viscosity measurements and density functional theory (DFT) calculations. The complex was demonstrated to act as a ct-DNA intercalator with a large DNA binding constant value of (6.06 +/- 0.32) x 10(6) m(-1) in 50 mm NaCl. The avid DNA binding affinity observed was rationalized by the DFT calculations. Copyright (C) 2011 John Wiley & Sons, Ltd.