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 boolean AND N)] PF6 (Ir-ANMM, tpy = 2-(p-tolyl)pyridine, N boolean AND 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 Ir-ANMM, which gives rise to a highly luminescent complex [Ir(tpy)(2)(N boolean AND N')]PF6 (Ir-HM, N boolean AND N' = 4-hydroxymethyl-4'-methyl-2,2'-bipyridine). Comparisons of the absorption, emission and mass spectra of Ir-ANMM in the absence and presence of HOCl have all confirmed the transformation of Ir-ANMM to Ir-HM. Titration and competition experiments have revealed high sensitivity and high selectivity of Ir-ANMM for HOCl, respectively. Significantly, the feasibility of the sensor under physiological conditions enables the successful luminescent imaging of HOCl in HeLa cells.