Ratiometric and highly selective fluorescent sensor for cadmium under physiological pH range: a new strategy to discriminate cadmium from zinc.

In a neutral aqueous environment, a new ratiometric Cd2+ fluorescent sensor 1a can successfully discriminate Cd2+ from Zn2+ by undergoing two different internal charge transfer (ICT) processes, and the high selectivity of sensor 1a to Cd2+ over some other metals was also observed. Moreover, through structure derivation and a series of NMR studies, the unique role of the 2-picolyl group (the part in red in the abstract graphic) in the sensor 1a-Cd2+ complexation was disclosed.