3‐Pyrrolyl BODIPY Based Schiff Base Fluorophores: A Selective Chemodosimetric and Optical Sensor for Diethyl Chlorophosphate

Diethyl chlorophosphate (DCP), an organophosphate, is utilized as a pesticide, herbicide, and for various other applications. Despite many uses of organophosphates, the organophosphates are noxious and harmful substances, and their selective detection is a critical concern in the context of the environment, physiology, and social security. In a methodological quest, here we have synthesized two Schiff base compounds 1 and 2 by introducing the hydroxyl group at the α-position of 3-pyrrolyl BODIPY either directly as hydroxylamine 1 or at the ortho position of aryl ring as 2-aminophenol 2. Both compounds 1 and 2 exhibited high selectivity and high sensitivity for DCP over other pesticides in the aqueous-alcoholic medium at physiological pH. This occurs via nucleophilic phosphorylation of the hydroxyl group, which resulted in both compounds exhibiting two different optical signals following the structure-function correlation of the pyrrolyl BODIPY systems. Upon binding DCP, compound 1 showed a quenching in the optical spectrum because of phosphorylation of hydroxyl group whereas compound 2 exhibited enhancements in both absorption and fluorescence spectra because of hydroxyl phosphorylation followed by intramolecular cyclization. Furthermore, the fluorescent microscopy experiments also indicated that the compound could be used as a fluorescent compound for sensing DCP in plant tissues.