A Ratiometric Fluorescent Probe for Cysteine and Homocysteine Displaying a Large Emission Shift

Abstract

4-(1H-phenanthro[9,10-d]imidazol-2-yl)benzaldehyde 1 was rationally designed as a novel ratiometric fluorescent probe for cysteine and homocysteine. Upon addition of cysteine or homocysteine, notably, the probe displayed a very large (125 nm) hypsochromic shift in emission due to switching off intramolecular charge transfer. This large emission wavelength shift may allow probe 1 to be employed for quantitatively detecting Cys/Hcy.