Experimental and theoretical studies on the structure, electronic and vibrational spectra of <i>o/p</i>-hydroxybenzylidene-<i>o/p</i>-toluidines

Abstract

The experimental and theoretical analyses of the electronic and vibrational spectra of four biologically active aldimines, i. e., <i>o/p</i>-hydroxybenzylidene-<i>o/p</i>-toluidines, using experimental techniques and semiempirical calculations are reported. Theoretical geometry optimization, and vibrational and electronic spectral studies have been computed in the gaseous phase at the PM3 and AM1 levels. The theoretical vibrational frequency data obtained from PM3 and AM1 level calculations are close to the experimental values. Geometrical optimization reveals that the two benzene rings of the aldimines are out-of-plane with respect to azomethine linkage (–C=N-). The electronic transitional energies of highest occupied molecular orbital and the lowest unoccupied molecular orbital energies calculated by FMO analysis predict the high reactivity of the molecules. The possible bonding sites of aldimines have been predicted by molecular electrostatic potential analysis. Various characteristics parameters such as electron affinity, ionization energy, hardness, softness, chemical potential and electrophilicity index of the focused aldimines are determined.