Novel cyclohexyl-containing N-salicylidene aniline Schiff bases: Synthesis, characterization, DFT studies, photophysical properties and potency against SARS-CoV-2 proteins

Two Schiff bases, namely N-cyclohexyl-3-methoxysalicylidenimine (1) and N-cyclohexyl-3-ethoxysalicylidenimine (2), which were synthesized by a condensation reaction of the 3-methoxy- or 3-ethoxysalicylaldehyde and cyclohexylamine, are reported. The formation of 1 and 2 was established by the FTIR and 1H NMR spectroscopy. Diffuse reflectance spectroscopy and UV-vis spectroscopy in n-hexane, CH2Cl2 and DMSO were applied to study optical properties of both compounds. Solutions of 1 and 2 in CH2Cl2 and DMSO were found to be emissive, while no emission was observed for solutions of both Schiff bases in n-hexane. The molecules 1 and 2 were studied by the DFT-based computations, electron localization function (ELF), localized orbital locator (LOL), non-covalent interactions (NCI) and reduced density gradient (RDG) plots to reveal their electronic and structural properties. Absorption, distribution, metabolism, excretion and toxicity (ADMET) properties of 1 and 2 were predicted using a set of online tools. Potential inhibition properties of the studied Schiff bases toward a number of the SARS-CoV-2 proteins were revealed using molecular docking and molecular dynamics simulations.