Some new details of the copper-hydrogen peroxide interaction

The addition of neocuproine (NC) or bathocuproine-disulphonate at the end of the autooxidation of Cu-I in phosphate buffer, pH 7.4, regenerates almost entirely the O-2 consumed. Other chelating agents assayed, including o-phenanthroline, cannot replace NC in promoting the O-2 formation. O-2 is also produced by adding NC to a mixture of Cu-II and H2O2 Concomitant with the O-2 evolution, the typical absorbance of the (NC)(2)Cu-I complex appears to account for the complete reduction of Cu-II to Cu-I. It is concluded that the addition of H2O2 with Cu-II produces the equilibrium Cu-II(O2H)(-) <-> (CdO2H)-O-I.. Addition of NC shifts the equilibrium to the right side by binding CuI. The released O-2(.-) then reacts with the remaining Cu-II yielding, in the presence of NC, the net reaction of 4 NC + 2 Cu-II + H2O2 --> 2 (NC)(2)Cu-I + O-2 + 2 H+. O-2 is also released in the absence of added NC provided the H2O2 concentration is increased. In these conditions the Cu-II(O2H)(-) complex undergoes other reactions leading to the copper-catalysed decomposition of H2O2. (C) 1997 Academic Press.