Synthesis and spectroscopic characterization of ternary copper(ii) complexes containing nitrogen and oxygen donors as functional mimics of catechol oxidase and phenoxazinone synthase

Abstract

Two ternary copper(II) complexes 1 [(Cu₂Me₄en)₄(EDTA)] and 2 [(CuMe₄en)₂(MIDA)] containing the mixed ligand system of 1,1′,4,4′-tetramethylethylenediamine (Me₄en) (L) and N-methyliminodiacetic (MIDAH₂) (L′) or ethylenediaminetetraacetic acid (EDTAH₄) (L′) were synthesized. Complete structural elucidation was achieved by many spectroscopic, electrochemical, and magnetic measurements. In addition, the spectral data of PXRD with Expo 2014's structural solution software were utilized for the structural illustration of the homobinuclear complex 1. Furthermore, the structural formulation of complex 2 was affirmed by the structural analysis of single-crystal X-ray. Square pyramidal geometry was suggested for both the homobinuclear and mononuclear complexes 1 and 2. The oxidase catalytic activities of complexes 1 and 2 were tested towards a series of catechols and o-aminophenol and the complexes were found to be promising functional mimics of catechol oxidase and phenoxazinone synthase. The tendency of the studied phenols to oxidize and transform to oxidation products is correlated with their binding affinity to the current complexes and the structure of the substrates. The driving force (λ) or the free energy change, −ΔG°, of the studied oxidation processes was computed from the electrochemical results. The plausible catalytic reaction pathways were suggested in light of the spectral, electrochemical, and stopped-follow kinetic measurements.