Kinetics of intra-polymer electron-transfer reactions in macromolecule–metal complexes

Abstract

A macromolecule–metal complex with redox centres on the same polymer chain of partially quaternized poly(1-vinylimidazole)(QPVIm) has been designed. In this complex, Co(tfacacen)(tfacacen =N,N′-ethylenebis(1,1,1-trifluoro-4-iminopentan-2-one), a Co^II–Schiff base complex, and quaternized imidazolium residues, an oxidizing agent, are both linked to a polymer backbone. The mechanism of the electron-transfer reaction between Co(tfacacen) and the quaternized imidazolium residue on this macromolecular complex have been investigated. The electron-transfer rate depends linearly on the concentration of Co^II residues and the degree of quaternization but is independent of the concentration of quaternized imidazolium residue. These dependencies indicate that, under the experimental conditions, an intra-polymer electron-transfer reaction occurs in this system. The reaction product formed by reduction of the quaternized imidazolium residue was identified by means of ¹H NMR and absorption spectroscopies. The results show that the predominant reduction product is 3-ethyl-4-imidazoline-containing polymer.