A rhodanine-based fluorescent chemosensor for sensing Zn²⁺ and Cd²⁺: Applications to water sample and cell imaging

A rhodanine-based chemosensor RDV, ((E)-3-((2-hydroxy-3-methoxybenzylidene)amino)-2-thioxothiazolidin-4-one), was designed and synthesized. Compound RDV displayed selectivity to Zn²⁺ and Cd²⁺ through marked fluorescence increase in aqueous media. Importantly, cysteine was used for distinguishing RDV-Zn²⁺ and RDV-Cd²⁺. RDV had low detection limits (1.07 μM for Zn²⁺ and 1.37 μM for Cd²⁺). RDV proved to be a practical sensor to water sample analyses and cell imaging. The sensing mechanisms of RDV to Zn²⁺ and Cd²⁺ were illustrated by ESI-mass, fluorescence, FT-IR, UV–visible spectroscopy and theoretical calculations.