An iridium(III) complex of oximated 2,2'-bipyridine as a sensitive phosphorescent sensor for hypochlorite

The designed synthesis of a sensitive phosphorescent chemosensor Ir(ppy)(2)(L1)](PF(6)) (1) (Hppy = 2-phenylpyridine, L1 = 4'-methyl-2,2'-bipyridyl-4-carbaldehyde oxime) was carried out for selective detection of hypochlorite (ClO(-)). Complex 1 is weakly emissive in solution at ambient temperature due likely to rapid isomerization of C=N-OH as an effective non-radiative decay process. When 1 reacts with ClO(-), however, the emission is remarkably enhanced, in which the oxime in L1 is converted to a carboxylic acid in L2 (4'-methyl-2,2'-bipyridine-4-carboxylic acid). The produced complex Ir(ppy)(2)(L2)](PF(6)) (2) exhibits bright orange-yellow luminescence originating from 5d(Ir) → π*(bpy)] (3)MLCT and π(ppy) → π*(bpy)] (3)LLCT triplet excited states as suggested from the DFT computational studies. The selective and competitive experiments reveal that complex 1 shows high sensing selectivity and sensitivity for ClO(-) over other reactive oxygen species (ROS) and metal ions.