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

(Chemical Equation Presented) 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 la to Cd ²⁺ 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.