Electron transfer macromolecular domain

Interfacial electron-transfer reactions between polymer-bonded metal complexes and the substrates in solution phase were studied to show colloid aspects of polymer catalysis. A polymer-bonded metal complex often shows a specifically catalytic behavior, because the electron-transfer reactivity is strongly affected by the pol)rmer matrix that surrounds the complex. The electron-transfer reaction of the amphiphilic block copol)rmer-bonded Cu(II) complex with Fe(II)(phenanthroline)3 proceeded due to a favorable entropic contribution, which indicated hydrophobic environmental effect of the copolymer. An electrochemical study of the electron-transfer reaction between a poly(xylylviologen) coated electrode and Fe(III) ion gave the diffusion constants of mass-transfer and electron-exchange and the rate constant of electron-transfer in the macromolecular domain. 

It is expected that the electron-transfer reactivity in a macromolecular domain is strongly influenced by the primary structure of polymer matrices, distribution of redox sites, charge density and polarity of polymer domain, etc. In order to assess these factors, the electron-transfer reaction of poly(xylyl-viologen) (5) with Fe(III) ion was selected for investigation. 

On the other hand, the 2 infinite value increases with the film thickness, which reflects an expansion of the macromolecular domain, i.e. increase of the redox sites. At intermediate thickness of the polymer layer, the electron-transfer reaction proceeds most rapidly. Further increase of the thickness brings about the steep decrease in the reaction rate via the electron-transfer process, probably caused by the decrease in the electron-transfer efficiency. 

Table II Diffusion constants of substrate (D cm /sec), of electron-exchange (D cm /sec), and rate constants of electron-transfer (kg 1/mol sec) in the macromolecular domain.

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