Iridium(III) complex of fluorinated cyclometalating ligands and imidazolium-bipyridine as an effective lifetime based phosphates sensor

Abstract

A new bis-heteroleptic cyclometallated Ir(III) complex, Ir-1 (C46H36F28IrN8P3), containing [3,5- difluoro-2-(5-trifluoromethyl-2-pyridinyl)phenyl] [dF(CF3)ppy] and 3,3′-([2,2′-bipyridine]-5,5′-diylbis(methylene))bis(1-ethyl-1H-imidazol-3-ium) has been synthesized and the solution structure was fully characterized by ESI-MS, NMR, UV–vis spectroscopy, and single crystal X-ray diffraction analysis. The fluorinated complex Ir-1 acted as a highly selective luminescent lifetime-based sensor for phosphates in CH3CN over other competitive anions. It has shown superiority in sensing phosphates as compared to previously reported non-fluorinated analog Ir-2 in CH3CN in terms of lower detection limit, enhanced binding constant, and longer excited state lifetimes. The implementation of [dF(CF3)ppy] ligand instead of 2-phenylpyridine (ppy) has improved the photoluminescence properties of Ir-1 as compared to Ir-2. Further, 1H NMR titration experiment established that the binding with these anions occurred exclusively through solitary neutral CH⋯anion hydrogen-bonding interactions.