Synthesis, X-ray crystallography, computational studies and catecholase activity of new zwitterionic Schiff base derivatives
Résumé
Three new Schiff bases compounds (L1-L2-L3) were synthesized by a condensation reaction in 1:1 M ratios of dehydroacetic acid (3-acetyl-6-methyl-2H-pyran-2,4(3H)-dione) and 4-fluoro/4-chloro/4-bromo aniline in ethanol, the products were obtained in excellent yields. Their structures were characterized by spectroscopic techniques (FT-IR and 1H NMR) and single-crystal X-ray diffraction. The three compounds display zwitterionic forms, with cationic iminium and anionic enolate groups. The aromatic ring and dehydroacetic acid ring are in a trans position with respect to the C=N bond. Calculations in the framework of the density-functional theory (DFT) were carried out to determine the optimized structures and electronic properties as the HOMO-LUMO energy gap. Hirshfeld surface analysis was used to support the packed crystal lattice 3D network intermolecular forces. The NH form is found to be more stable than OH form. On the other hand, the in situ generated copper (II) complexes were examined for their catalytic activities and were found to catalyze the oxidation reaction of catechol to o-quinone under atmospheric dioxygen. The present study reveals that the rate of oxidation depends on the nature of the substituents in the phenyl ring, the counter anion and the concentration of ligand. The combination L1(Cu(CH3COO)2) gives the highest rate.
Domaines
Chimie théorique et/ou physique
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