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

A new binuclear copper(II) complex [Cu-2(H(-4)tapt)]. 10H(2)O, where tapt i s N,N',N ",N'''-tetra(2-aminopropyl)-1,1,2,2-ethanetetraamide, has been syn thesized and investigated in detail as a mimic of superoxide dismutase. Cry stal structure analysis shows that each copper atom is situated in a slight ly distorted square-pyramidal environment, with a water molecule at the ape x. According to the result of pulse radiolysis, the complex has a high rate constant toward O-.(2)-, k(cat)=1.91x10(8) dm(3) mol(-1) s(-1) (pH 7.4). P otentiometric titration shows that the mimic exhibits high stability at phy siological pH value (7.4). EPR and ES-MS spectra reveal intermolecular inte raction of two copper(II) nuclei.