Electron-transfer reaction of a copper(II) complex bound to an amphiphilic block copolymer: A plastocyanin model

A water-soluble tri-block copolymer ( 1 ) composed of hydrophilic poly(ethylene oxide) and hydrophobic poly(styrene-co-1-vinylimidazole) was synthesized as a model compound of the apoenzyme of plastocyanin. Visible and electron spin resonance spectra of the Cu complex bound to the imidazole residue of 1 showed that the Cu complex is surrounded by a hydrophobic domain even in aqueous medium. The outer-sphere electron-transfer reaction of Cu(II) with Fe(II) (phenanthroline)₃ proceeded faster (with a large activation entropy) for the polymeric Cu/ 1 complex than for the monomeric Cu/1-ethylimidazole complex, while the reduction with ascorbic acid was slower for the polymeric complex.