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

Abstract

The designed synthesis of a sensitive phosphorescent chemosensor [Ir(ppy)₂(L1)](PF₆) (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 CN–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)](PF₆) (2) exhibits bright orange-yellow luminescence originating from [5d(Ir) → π*(bpy)] ³MLCT and [π(ppy) → π*(bpy)] ³LLCT 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.