Four phosphorescent iridium(III) complexes containing brominated 2,2′- bipyridine ligands as efficient chemosensors for OH- ions

Four cationic Ir(III) complexes Ir1-Ir4, [(4-fpiq)2Ir(L1)]PF6 (Ir1, 4-fpiq = 1-(4-fluorophenyl)isoquinoline, L1 = 4,4 '-dibromo-2,2 '-bipyridine), [(4-fpiq)2Ir(L2)]PF6 (Ir2, L2 = 5,5 '-dibromo-2,2 '-bipyridine), [(4-chopiq)2Ir(L1)] PF6 (Ir3, 4-chopiq = 1-(4-formylphenyl)isoquinoline), [(4-chopiq)2Ir(L2)]PF6 (Ir4) were synthesized using 2,2 '- bipyridine derivatives as neutral ligands. These complexes show decent orange and red phosphorescence (lambda em = 576-618 nm) with quantum efficiencies of 0.13-0.37. The influence of substituents in the ligands on the photophysical and electrochemical properties of the Ir(III) complexes was investigated by UV-vis absorption and emission spectra and cyclic voltammograms and simulated by density functional theory (DFT) calculations. Upon addition of OH- ions to the solutions of Ir1-Ir4, all the complexes exhibited a turn -on response to OH- with a low detection limit on the order of 10-6 M, and high selectivity to OH- was demonstrated.