Low Molecular Weight Fluorescent probes for the detection of organophosphates

Three Low Molecular Weight Fluorescent probes (LMFPs) coumarin-enamine (3a-c) have been synthesized, and their photophysical properties studied in different solvent systems (DMSO, CH3CN, DMF, MeOH, EtOH, Me2CO, MeCO2Et, CHCl3, C6H5Me, C6H6). Dimethyl sulfoxide was chosen as the optimum to investigate 3a for organophosphate detection. On deprotonation of oxime, a significant spectroscopic shift is observed UV–Vis spectrum (Δ ≈ 35 nm). The fluorescence shows broad featureless band at 535 nm that shifts hypochromically. Both UV–vis spectra undergo drastic optical responses when OP-adduct formed. Diisopropyl chlorophosphate found most extensive changes among phosphorus (V) center OPs investigated (diisopropyl chlorophosphate, diisopropyl fluorophosphate (DFP), dimethoate, omethoate, chlorfenvinphos, carbaryl). turn “off-on” response consequence PET mechanism, supported by molecular modeling calculations. A limit detection calculated be 1.1 ppm DFP (a nerve agent simulant). Fluorescence lifetime studies were carried out, which showed decay times 3a, its oximate, DCP-adduct τ = 1.56, 3.23, 1.55 ns, respectively, aid our understanding selectivity.