A superoxide dismutase mimic with high activity: crystal structure, solution equilibrium and pulse radiolysis

Abstract

A new binuclear copper(II) complex [Cu₂(H₋₄tapt)]·10H₂O, where tapt is N,N′,N′′,N′′′-tetra(2-aminopropyl)-1,1,2,2-ethanetetraamide, has been synthesized and investigated in detail as a mimic of superoxide dismutase. Crystal structure analysis shows that each copper atom is situated in a slightly distorted square-pyramidal environment, with a water molecule at the apex. According to the result of pulse radiolysis, the complex has a high rate constant toward ˙O₂⁻, k_cat = 1.91 × 10⁸ dm³ mol⁻¹ s⁻¹ (pH 7.4). Potentiometric titration shows that the mimic exhibits high stability at physiological pH value (7.4). EPR and ES-MS spectra reveal intermolecular interaction of two copper(II) nuclei.