Structural conformations and density functional study on the intramolecular charge transfer based on vibrational spectra of 2,4-dihydroxy-N′-(4-methoxybenzylidene)benzohydrazide

The NIR-FT Raman and FT-IR spectra of 2,4-dihydroxy-N′-(methoxybenzylidene) benzohydrazide (DMBBH) molecule have been recorded and analyzed. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level has been used to compute energies of different conformers of DMBBH to find out their stability, the optimized geometry of the most stable conformer and its vibrational spectrum. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra and calculated vibrational modes and potential energy distribution over the internal coordinates. The vibrational analysis confirm the charge transfer interaction between the phenyl rings through CNN skeleton. The broadening of the band at 1631 cm−1 and the appearance of the band at 1556 cm−1 strongly suggests the existence of proton equilibrium.

Graphical abstractThe experimental and theoretical vibrational analysis of 2,4-dihydroxy-N′-(4-methoxybenzylidene)benzohydrazide has been performed. The molecular geometry, vibrational wavenumber, infrared and Raman intensities of the molecule in the ground state have been calculated by using DFT method.The NBO analysis explained the intramolecular hydrogen bonding and the hyperconjugative interaction. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra and calculated vibrational modes and potential energy distribution over the internal coordinates.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Vibrational spectra of the 2,4-dihydroxy-N′-(4-methoxybenzylidene)benzohydrazide have been analyzed. ► The computed vibrational wavenumbers were seen to be in good agreement with the experimental data. ► Conformation analysis. ► The natural bond orbital (NBO) analysis has been carried out.