Engineering of efficient phosphorescent iridium cationic complex for developing oxygen-sensitive polymeric and nanostructured films

In this study, a novel phosphorescent Ir(III) complex [Ir(2-phenylpyridine)2(4,4'-bis(2-(4-N,N-methylhexylaminophenyl)ethyl)-2-2'-bipyridine)Cl] (for convenience, the complex was given the synonym N-948) has been designed and synthesized, to be used as an oxygen probe. It was characterized by spectroscopic and analytical methods when incorporated in a polystyrene and nanostructured metal oxide support. N-948 is the first Ir complex in the literature with a luminescence emission at a wavelength higher than 650 nm (665 nm), with a quantum yield higher than 0.50 (0.58 +/- 0.05) and an extremely long phosphorescence lifetime (102 micros) which has been used for developing oxygen-sensitive films. In addition, the new complex shows a Stern-Volmer constant which is 20 times higher than that of other Ir complexes known from the literature when they are immobilized in polystyrene. The sensing film shows long-term stability (up to 12 months), complete reversibility of the signal quenched by oxygen and a quick response time to various oxygen concentrations (<2 s changing from 10 vol% pO2 to 90 vol% pO2). Thus, it is an interesting and promising complex for developing oxygen-selective sensors for gas analysis and the analysis of dissolved oxygen.