A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome oxidase.

In mitochondria, cytochrome oxidase (CO) catalyses the reduction of oxygen (O) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CO. A tridentate copper(ii) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(iii) (FeTPPS) through supramolecular complexation between FeTPPS and a per--methylated β-cyclodextrin dimer linked by a (2,2':6',2''-terpyridyl)copper(ii) complex (CuTerpyCD). The reduced FeTPPS/CuTerpyCD complex reacted with O in an aqueous solution at pH 7 and 25 °C to form a superoxo-type Fe-O/Cu complex in a manner similar to CO. The pH-dependent autoxidation of the O complex suggests that water molecules gathered at the distal Cu site are possibly involved in the Fe-O/Cu superoxo complex in an aqueous solution. Electrochemical analysis using a rotating disk electrode demonstrated the role of the FeTPPS/CuTerpyCD hetero-binuclear structure in the catalytic O reduction reaction.