Catecholase catalytic properties of copper (II) complexes prepared in-situ with heterocyclic ligands: Experimental and DFT study

The objective of our work is the preparation of the new catalysts for catecholase, whose principle is based on the catechol oxidation reaction which presents a major challenge in both biology and medicine. First, we synthesized nine pyrazole and triazole ligands, then we evaluated the catalytic properties of certain of those ligands in situ complexes to catalyze the oxidation reaction of catechol to o-quinone. The aim of this study is to find the right models to reproduce the catalytic activity of the enzyme (catecholase), so we used complexes formed in situ by pyrazole and triazole derivatives with copper (II) salts. The reason behind the interest of these complexes is their resemblance to biological systems, capability of activating the catalyst for many chemical reactions. Among these complexes, some of them showed good catalytic activity for this reaction. We have demonstrated that the nature of ligand, the concentration of ligand, the nature of the solvent and the nature of the copper (II) salt, influences the efficiency of the catecholase activity. Pyrocatechol is benzene-1,2-diol (nomenclature IUPAC), also known as catechol with formula C 6 H 6 O 2 crude used in many organic syntheses. Some catecholamines have important physiological functions. The Government of Canada has determined that catechol is "toxic" as defined by the Canadian Environmental Protection Act, 1999. So, to reduce the toxic effect of catechol we try to oxidize o-quinone which is less dangerous than catechol. The DFT study has big interest in many researches to know the reactivity of the ligands by calculating different quantum descriptors as: EHOMO, ELUMO, The gap energy, Ionisation potential, The electron affinity and The hardness.