Two ternary copper( ii ) complexes 1 [(Cu ₂ Me ₄ en) ₄ (EDTA)] and 2 [(CuMe ₄ en) ₂ (MIDA)] containing the mixed ligand system of 1,1′,4,4′-tetramethylethylenediamine (Me ₄ en) (L) and N -methyliminodiacetic (MIDAH ₂ ) (L′) or ethylenediaminetetraacetic acid (EDTAH ₄ ) (L′) were synthesized.

A series of macrocyclic complexes, [Cu(TAAP)]X₂, X = ClO₄ and CH₃COO; [Cu(TAAP)X]X, X = NO₃, Cl, and Br, have been synthesized by self-condensation of 5-amino-3-methyl-l-phenylpyrazole-4-carbaldehyde (AMPC) in the presence of copper(II). Elemental analyses and conductivity measurements confirm the stoichiometry of the ligand and complexes, while the characteristic absorption bands in IR spectra confirmed the formation of ligand framework around copper. Square-pyramidal and square-planar stereochemistries have been proposed for the five-coordinate (nitrato and halogeno) and four-coordinate (perchlorate and acetate) complexes. The electrochemical properties and thermal behaviors have been studied by cyclic voltammetry and TGA. Mimetics of antioxidant enzymes such as superoxide dismutase (SOD) and catalase demonstrated that there is a correlation between the observed redox properties and the SOD and catalase biomimetic catalytic activities of the copper(II) complexes.

The synthesis of new tetradentate Schiff-base containing N₄ donors is described along with the preparation of a series of copper complexes derived from this ligand. These complexes have the form [CuLX]X′, X = OH⁻, X′ = (1) or X = X′ = Cl⁻ (2); and [CuL]H₂O(ClO₄)₂ (3), in addition to a copper(I) complex [Cu₂L₂](ClO₄)₂ (4). The synthesized compounds were spectroscopically characterized, showing the N₄ donor ligand. The single-crystal X-ray structural analysis of 4 demonstrated the dimeric structure and univalent copper. This dimer consists of , two uncoordinated , and one acetonitrile. Each ligand is tetradentate via pyridyl and azomethine nitrogen atoms, providing a strongly distorted tetrahedron around copper(I) despite the pseudo-macrocyclic skeleton of the ligand. These complexes have been evaluated as functional model systems for catechol oxidase enzyme using 3,5-di-tert-butylcatechol (3,5-DTBC) as the test substrate. The catalytic performance of the air oxidation of 3,5-DTBC to the corresponding light absorbing 3,5-di-tert-butylquinone (3,5-DTBQ) at ambient conditions was studied using UV-Vis absorption spectra. Complex 4 exhibits the highest catalytic activity with turnover number of 33 h⁻¹. A kinetic treatment on the basis of the Michaelis–Menten model was applied. Correlation among reactivity, binding constants, electrochemical properties, and the geometry was determined. These correlations showed that the rate of oxidation is linearly correlated with the binding constants for the five coordinate 1 and 2. The catalytic investigations demonstrate that geometrical effects are only one facet of the activity. The probable mechanistic implications of the catalyzed oxidation reactions are discussed.