Synthesis, molecular structure analyses and DFT studies on new asymmetrical azines based Schiff bases

Abstract : In this paper, we report the synthesis of new unsymmetrical azines Schiff bases. These compounds were prepared by condensation of hydrazine with different aldehydes and ketones to give (E) -2-hydroxynaphthalene-1-carbaldehyde [(1E) -2-thienylmethylene] hydrazone compound (I) and (Z) - 2 - [(E) -1- (2-hydroxyphenyl) ethylidenehydrazin-1-ylidene] -1,2-diphenylethanone compound (II). The method adopted consists in reacting the two different carbonyl compounds simultaneously in one step in a stepwise manner reported which is practical and cost-effective. The reaction with a minor modification in operating conditions proceeded efficiently and with excellent performance. The structure of each of the two compounds (I) and (II) was determined by the X-ray diffraction technique performed on single crystals. The asymmetric unity of the two molecules consists of one asymmetry-independent molecule. In addition, hydrogen bonds CH … π are observed in the compound (II). We then present a detailed DFT study based on B3LYP/6-31G (d, p) geometric structures of compounds (I); (II) and another compound (III) also another asymmetric azine (Z) -2 - [(E) -2-benzylidenehydrazine-1-ylidene] -1,2-diphenylethanone whose crystal structure is reported. The fundamental vibration wave numbers are calculated and a good agreement between the observed and calculated wave numbers is obtained. The study was extended to the HOMO-LUMO analysis to calculate the energy gap. The calculated HOMO and LUMO energy reveals that the charge is transferred into the molecule.