A water-soluble and highly phosphorescent cyclometallated iridium complex with versatile sensing capability

A water-soluble and highly phosphorescent cyclometallated iridium complex [(pq)2Ir(bpy-COOK)]+Cl- (where pq=2-phenylquinoline, bpy-COOK= potassium 2,2′-bipyridine-4,4′-dicarboxylate) (Ir) has been synthesized and characterized. Its phosphorescence can be sensitively and selectively quenched by tryptophan through a photoinduced electron-transfer (PET) process. Furthermore, the phosphorescence of Ir is drastically increased upon binding with bovine serum albumin (BSA), and the enhanced signal is effectively quenched in the presence of Cu2+. Thus, Ir can be used as a multifunctional chemosensor for tryptophan, BSA, and Cu2+ determination as well as for cell imaging. A water-soluble cyclometallated iridium complex with its phosphorescence sensitively and selectively responsive to tryptophan, bovine serum albumin and copper ions. [Display omitted] •A water-soluble and highly phosphorescent iridium complex was synthesized and characterized.•The phosphorescence of the Ir complex can be sensitively and selectively quenched by tryptophan.•The phosphorescence of the Ir complex is further enhanced upon binding with bovine serum albumin.•The enhancement in the phosphorescence of Ir complex by bovine serum albumin can be effectively quenched by Cu2+.•The iridium complex can not only serve as a multifunctional chemosensor, it can also be used for cell imaging.