Factorial design analysis of the catalytic activity of di-imine copper(II) complexes in the decomposition of hydrogen peroxide

Factorial design analysis was applied to the study of the catalytic activity of diimine copper(II) complexes, in the decomposition of hydrogen peroxide. The studied complexes show a tridentate imine ligand (apip), derived from 2-acetylpyridine and 2-(2-aminoethyl)pyridine, and a hydroxo or an imidazole group at the fourth coordination site of the copper ion. The factorial design models for both [Cu(apip)imH](2+) and [Cu(apip)OH](+) were similar. increasing the peroxide concentration from 3.2 x 10(-3) to 8.1 x 10(-3) mol L-1 resulted in increased oxygen formation. Increasing the pH from 7 to I I also increased oxygen formation and had an effect about twice as large as the peroxide one. Both complexes also had an important interaction effect between peroxide concentration and pH. However, increasing the catalyst concentration led to a decrease in total oxygen formation. The obtained results were corroborated by further data, achieved by using the usual univariate method, and helped to elucidate equilibrium steps occurring in the studied systems. in very alkaline solutions, the studied [Cu(apip)imH](2+) complex can form the corresponding dinuclear species, [Cu-2(apip)(2)im](3+). While the mononuclear complex proved to be an efficient catalyst in hydrogen peroxide decomposition, the corresponding dinuclear compound seemed to be able to coordinate with the dioxygen molecule, inhibiting its observed release. (C) 2001 John Wiley & Sons. Inc.