Discrimination of Cys from Hcy by an Iridium(III) Complex Based on Time-Dependent Luminescence

A phosphorescent probe, Ir(ppy)2Cl(DMF) (Ir2), for cysteine (Cys) is reported. The recognition is based on the time-dependent emission of Ir2-Cys. Importantly, this probe can discriminate Cys rapidly from homocysteine (Hcy). Probe Ir2 displays a highly selective 72 nm of luminescent red-shift toward Cys within 30 min with an obvious emissive color change from green to orange. After 30 min, the emission band blue shifts gradually with an emissive change from orange to green. TDDFT combined with CV studies indicates that the different emission profile is ascribed to the different binding modes of Ir2 to Cys with time. The probe can be used to determine Cys in semiaqueous solution.