Experimental and theoretical studies of the vibrational and electronic properties of (2E)-2-[3-(1H-imidazol-1-yl)-1-phenylpropylidene]-N-phenylhydrazinecarboxamide: An anticonvulsant agent

In the current investigation, the molecular structure of the anticonvulsant agent (2E)-2-[3-(1H-imidazol-1-yl)-1-phenylpropylidene]-N-phenylhydrazinecarboxamide ((2E)-HIPC) was theoretically modelled using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) calculations. The Fourier transform (FT) infrared and FT-Raman spectra of (2E)-HIPC were also recorded, and the observed bands were assigned to the vibrational normal modes. The main functional groups were identified via vibrational analysis, and their absorption bands were assigned. A comparative analysis was performed for the computed and experimental results. Subtle differences were observed between the calculated and experimental UV-Vis spectra. Time-dependent density functional theory (TD-DFT) excitation energies were calculated for five excited electronic states. The calculations were applied to simulate the spectra of (2E)-HIPC, and these simulated spectra exhibited excellent agreement with the experimental spectra. The DFT/B3LYP/6-311++G(d,p) method, after scaling, exhibited better agreement with the experimental values than the results obtained by the HF method. The energy, oscillator strength, and wavelength computed by TD-DFT (IEFPCM) are consistent with the experimental results. The molecular electrostatic potential (MEP) and frontier molecular orbitals (HOMO-LUMO) were also determined to enable prediction of the structural changes and reactive sites. Mulliken population charges of the title molecule were also calculated in the gas phase. The NMR chemical shifts (¹³C and ¹H) were calculated using the gauge-including atomic orbital method and the B3LYP/6-311++G(d,p) approach and were compared with the experimental values.