Rhodamine and functionalised azobenzene condensed fluorescent <i>turn on</i> novel receptor for the selective and sensitive detection of Hg ²⁺ : a combined experimental and theoretical study

Rhodamine dye has a high absorption coefficient, fluorescence quantum yield, photostability, and extended wavelengths that make it a promising fluorescent probe. A rhodamine and functionalised azobenzene condensed novel chemosensor L has been reported for the first time to detect Hg²⁺ in aqueous ethanol optically in this investigation. Chemosensor L's fluorescence activation in response to Hg²⁺ is due to the suppression of PET and CHEF processes and the change from spirolactam to ring-opened amide. Time-resolved photoluminescence studies confirmed the PET and CHEF processes, whereas ¹³C-NMR and infrared spectroscopy confirmed the spirolactam ring opening. The opened spirolactam ring forms a 1 : 1 binding complex with Hg²⁺, as shown by its high binding constant. L can be successfully applied for the formation of a INHIBIT type of logic gate and real sample analysis.