Detection mechanism of glutathione by off–on fluorescent probe based on excited state intramolecular proton transfer

The mechanism of Glutathione detection probes 2-(benzo[d]thiazol-2-yl)-6-formyl-4-methylphenyl 2,4-dinitrobenzenesulfonate (BTFMD) and BTFM-OH have been investigated. The analysis of structural parameters, interaction region indicator (IRI) value and infrared vibration spectra show the hydrogen bond is strengthened in the S1 state, which is beneficial to excited state intramolecular proton transfer (ESIPT). Combined with hole electron analysis and frontier molecular orbitals (FMOs), the electron density of BTFMD is transferred from benzothiazole and 5-methylsalicylaldehyde to 2,4-dinitrobenzenesulfonyl and the fluorescence properties changed due to photoinduced electron transfer (PET). The potential energy curve explains the single fluorescence emission and the ESIPT process in the S1 state.