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

Abstract

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 C=N-N 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.