The synthesis of 3-ethyl-5-methyl-2,6-diarylpiperidin-4-on-1-ium picrates and their spectral, XRD and theoretical studies

Three 3-ethyl-5-methyl-2,6-diarylpiperidin-4-on-1-ium picrates (1-3) (aryl = C6H5, p-FC6H4 and p-CH3OC6H4,) have been synthesized by mixing 3-ethyl-5-methyl-2,6-diarylpiperidin-4-one and picric acid. The synthesized compounds were characterized by elemental analysis, FT-IR spectroscopy and NMR spectroscopy. The obtained conformation of compound 3 was determined by single crystal XRD analysis. The crystallographic data revealed that the spatial structure of the title crystals adopted a chair conformation. Additionally, the synthesized compounds 1-3 were subjected to UV-visible, fluorescence and DFT studies for a better understanding of the molecular design and optoelectronic properties. The optimized geometric parameters were in agreement with the corresponding experimental values. The Mulliken and MEP analyses were utilized to spot the reactive sites of the compounds. The intermolecular and intramolecular delocalization and donor-acceptor interactions were ensured by the NBO analysis. The calculated HOMO and LUMO energies exhibited that the charge transfer happened within the molecule. The polarizability and hyperpolarizability values showed that the compounds possessed a non-linear optical nature.