Synthesis, spectrophotometric pH titrations and DNA binding properties of a cyclometalated iridium(III) complex of tetrapyrido[3,2-a:2′,3′-c:3,2-h:2′,3′-j] phenazine

A new cyclometalated iridium(III) complex [Ir(ppy)(2)(tpphz)] Cl {Hppy - 2-phenylpyridine and tpphz - tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2 ''',3 '''-j] phenazine} has been synthesized and characterized. The pH effects on UV-vis absorption spectra have been studied, and three ground-state acidity ionization constant values have been derived. The calf thymus (ct) DNA binding properties of the complex have also been investigated with UV-vis absorption spectrophotometric titrations, DNA competitive binding with ethidium bromide, DNA melting experiments, viscosity measurements, and density functional theory calculations. The complex was demonstrated to act as a DNA intercalator with a binding constant of (9.29 +/- 1.26) x 10(5) M-1 more than one order of magnitude greater than that previously reported for DNA intercalator of [Ir(ppy) 2(dppz)](+). (C) 2010 Elsevier B. V. All rights reserved.