Vibrational spectroscopic studies, NMR, HOMO–LUMO, NLO and NBO analysis of 1-(2-nitrobenzoyl)-3,5-diphenyl-4,5-dihydro-1 H -pyrazole with use X-ray diffractions and DFT calculations

Abstract The crystal and molecular structure of the title compound, 1-(2-nitrobenzoyl)-3,5-diphenyl-4,5-dihydro-1 H -pyrazole, was reported and confirmed by single crystal X-ray diffraction and spectroscopic data. The structure, geometry optimization, vibrational frequencies and nuclear magnetic resonance were also investigated. Stability of the molecule arising from hyperconjugative interactions and charge delocalisation was analysed using natural bond orbital analysis. The results show that charge in electron density (ED) in the σ ∗ and π ∗ antibonding orbitals and second-order delocalisation energies E(2) confirms the occurrence of intramolecular charge transfer within the molecule. Satisfactory theoretical aspects were made for the stable conformer of the molecule using density functional theory DFT-B3LYP methods with the 6-311G++(d,p) basis set.