Synthesis and in silico studies of quinoline appended acridine via conventional and green methods: photophysical analysis of novel fluorophore for picric acid detection using a ‘turn-off' fluorescence approach

A series of novel 4-(9-phenyl-1,2,3,4-tetrahydroacridin-2-yl)cyclohexan-1-ones and their dimers were synthesized using an efficient one-pot method with Deep Eutectic Solvents (DESs), alongside microwave-assisted and conventional techniques. Using less toxic and inexpensive DESs enhance sustainability in producing desired products. Green metrics calculations indicate a high level of greenness in the synthesis process. FT-IR, NMR, and HRMS characterized the compounds. In-silico tests involving Bovine Serum Albumin (BSA) assessed the binding affinity of the compounds toward various drugs. Furthermore, DFT studies explored theoretical spectral calculations, energy differences, and electron cloud density. Notably, among the derivatives, the fluorophore 4-(7-amino-9-phenyl-1,2,3,4-tetrahydroacridin-2-yl)cyclohexan-1-one (3e) can specifically detect 2,4,6-trinitrophenol (Picric acid, PA), a fatal nitro explosive. Photophysical studies confirmed 3e's ability as a "turn-off" fluorescence chemosensor for PA with a detection limit of 1.766 × 10^-9 M and a binding stoichiometric ratio of 1:1 between the probe and analyte. Structural confirmation of the probe was achieved through single-crystal XRD.