Catecholase Activities of Copper(II) Complexes With N₄ Ligands

Two new N₄ ligands, 1,2-bis(2-((pyridine-2-yl)methyleneamino) phenyl)ethane (L¹) and tris((2-benzylideneamino) ethyl)amine (L²), derived from 2,2′-ethylenedianiline and tren, respectively, were developed and their copper(II) complexes [Cu(L¹)(ClO₄)](ClO₄)CH₃OH∙H₂O and [Cu(L²) (CH₃COO)](ClO₄) were synthesized. Crystal structures of the complexes were determined to show that both the complexes have distorted square pyramidal coordinations with very similar geometrical parameters. Catecholase activities of the complexes were investigated for the oxidation of 3,5-di-tert-butylcatechol (3,5-H₂dtbc) to 3,5-di-tert-butyl-o-quinone (3,5-dtbq) in the presence of O₂. Kinetic behaviors and spectroscopic measurements on the catalytic reactions were supportive to the proposal in which the mechanical pathway of the catecholase activities by the complexes were initiated by the anaerobic oxidation of 3,5-H₂dtbc to 3,5-dtbq, followed by the catalytic cycles with Cu(I) active forms.