A highly selective and sensitive turn-on chemodosimeter for hypochlorous acid based on an iridium(III) complex and its application to bioimaging.

A novel and easily accessible luminescent iridium(iii) complex [Ir(tpy)2(N^N)]PF6 (, tpy = 2-(p-tolyl)pyridine, N^N = 4-[(4-amino-3-nitrophenoxy)-methylene]-4'-methyl-2,2'-bipyridine) for the sensing of HOCl has been designed and synthesized. The detection strategy is based on the HOCl-promoted cleavage of the PET quenching 4-amino-3-nitrophenyloxy moiety of the weakly emissive complex , which gives rise to a highly luminescent complex [Ir(tpy)2(N^N')]PF6 (, N^N' = 4-hydroxymethyl-4'-methyl-2,2'-bipyridine). Comparisons of the absorption, emission and mass spectra of in the absence and presence of HOCl have all confirmed the transformation of to . Titration and competition experiments have revealed high sensitivity and high selectivity of for HOCl, respectively. Significantly, the feasibility of the sensor under physiological conditions enables the successful luminescent imaging of HOCl in HeLa cells.