A reaction based chromofluorogenic turn-on probe for specific detection of fluoride over sulfide/thiols

A new reaction based probe fluorescein nosylate (R1) has been designed and synthesized for selective recognition of F− in acetonitrile (CH3CN) by exploiting both its nucleophilic and basic character. Probe R1 consists of fluorescein dye as a signalling unit while 4-nitrobenzenesulfonyl chloride as the masking unit. The F− plays the role of de-masking agent to set free the fluorescein moiety in its open form from R1 leading to significant changes in its absorption/emission profile. The detection of F− amidst of sulfide/thiols through receptors undergoing nucleophilic scission is a tedious job due to similarity in their extent of basicity/nucleophilicity. Here, we present a convenient solution for the same in the form of R1 which detects F− selectively over sulfide/thiols in CH3CN with a high detection limit of 4.6 × 10−7 M and 2.75 × 10−8 M determined through UV–visible and fluorescence titration data, respectively.