Synthesis and photophysical properties of iridium-lanthanide complexes containing pyridine and phenazine ligands and NIR probe for DNA

Abstract

A series of iridium-lanthanide complexes [Ir(ppy)2(tpphz)Ln(TTA)3]Cl (Ln = Nd(Ⅲ), Yb(Ⅲ), Er(Ⅲ), Gd(Ⅲ); ppy = phenylpyridine; tpphz = tetrapyrido[3,2- a :2,3- c :3,2-h:3,4- j ]phenazine) containing pyridine and phenazine ligands have been designed and synthesized. They were characterized by IR spectroscopy, ESI-MS spectrometry, elemental analysis, and their photophysical properties in the solid states and solutions were studied. It is found that sensitized near-infrared (NIR) luminescence is observed from Nd and Yb centre following excitation of the iridium complex in the solid state, in CH2Cl2 solution and in Tris-HCl buffer solution (pH 7.2) at 298 K, which results from the effective Ir → Ln (Ln = Nd, Yb) energy transfer. A new NIR luminescence probe for DNA is established based on quenching the NIR emission intensity of the Ir - Yb complex by DNA, which may provide preliminary experimental data of Ir - Yb complex as biological probes.