Synthesis, conformational study and DFT analysis of novel nonlinear optically active 2r,6c-diaryl-3t-methylpiperidin-4-one N-(2′-furoyl)hydrazones

Abstract

A series of nonlinear optical (NLO) active 2-furoic acid hydrazide derivatives, 2r,6c-diaryl-3t-methylpiperidin-4-one N-(2′-furoyl)hydrazones (6–10), were synthesized. The structures of these hydrazones were confirmed unambiguously by Fourier transform infrared spectroscopy, mass spectrometry, elemental analysis, 1H, 13C, HOMO-COSY, HSQC, and HMBC nuclear magnetic resonance spectroscopy. The piperidine core of all the targeted hydrazones (6–10) adopted the chair conformation with the equatorial orientations of all the substituents and the ‘E’ configuration about the C=N bond observed. Density functional theory using the B3LYP/6–31G(d,p) level of theory indicated that all hydrazones favor the ‘E’ isomer state. The Mulliken population, frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) surfaces, and reactivity parameters were also evaluated and showed a good correlation with the experimental data. The efficiency of hydrazones (6–10) in terms of the nonlinear optical (NLO) activity was proven, and the hydrazones (6–10) showed higher NLO activity compared to that of the reference molecule, as determined by the molecular hyperpolarizability measurements. The structural, spectral, and electrochemical properties were also determined, and DFT analysis was consistent with the experimental outcomes. The FMO, MEP, and reactivity parameter analyses revealed intramolecular charge transfer and high reactive features, leading to superior NLO property of hydrazones (6–10).