1,10-phenanthroline appended novel Schiff base as a selective fluorescent chemosensor for nerve agent stimulants

A simple, tailor-made, novel chemosensor based on 1,10-phenanthroline Schiff base incorporating N, N-Diethylamino salicylaldehyde (1) was designed and synthesized. The sensing ability of chemosensor 1 was tested via colorimetric, UV-Vis and fluorescence spectroscopy. Chemosensor 1 could effectively and specifically detect diethylchlorophosphate (DCP) in acetonitrile displaying naked eye colour change from pale yellow to dark yellow while fluorogenic colour changes from blue to pink fluorescence (365 nm UV lamp irradiation). The spectral changes corroborated the colorimetric results with appreciable bathochromic shifts of 44 and 75 nm in absorption and emission spectra respectively. With DCP, the spectral changes may be attributed to the reaction of the phosphorus group with the hydroxyl group which inhibits the ICT within the molecule. The colorimetric and spectral changes were reversed with the addition of triethylamine (TEA) signifying the reversibility of chemosensor 1. Significantly, the detection limit of 1 for DCP ions was evaluated to be 4.4 nM with the binding constant value of 1.9 × 10⁴ M^-1. Furthermore, chemosensor 1 showed excellent performance for convenient DCP detection via filter paper fabricated test strips.