Poly , electron-transfer

The forward ET rate for the poly(A/St/Phen)-MV2 + system was extremely fast i.e., the rate constant (kEX) was at least of the order of 1011 s It is reasonable to consider that the fast primary electron transfer occurs from D to the... 

F. la-c. Cyclic voltammograms of dissolved and stance confined ferrcx ne in a< tonitrile/0.1 M TBAP. a. 4 X 10 M dissolved ferrocene at Pt. b. 4-ferrocenyl-phenylacetamid monolayer bound to Pt (ref. ). c. Poly-vinylferrocene dip coated on Pt,r = 1 x lO raolcm. Straight arrows indicate diffusional events. Curved arrows electron transfer events (from ref. ). 

Similarly, energy-transfer processes, together with electron transfer and hydrogen abstraction reactions could be induced in poly(organophosphazenes) in an intramolecular way by preparing POPs geminally substituted at the same phosphorus with two different substituent groups. 

The cobalt(II)15 and zinc(II)16 complexes of phthalocyanine(Pc), octcyano-Pc, and tetrasulfon-ato-Pc incorporated in poly(4-vinylpyridine-co-styrene) or Nafion films coated on graphite have also been examined as catalytic devices for dihydrogen electrogeneration in phosphate buffer. These catalytic systems were strongly suggested to be dominated by the electron transfer within the polymer matrix. The best catalytic film is that constituted of the nonsubstituted Con-Pc complex in poly(4-vinylpyridine-co-styrene), giving a turnover number of 2 x 10s h-1 at an applied potential of —0.90 V vs. Ag Ag Cl. 

Fig. 1.16 Schematic representation of the nanofibrous poly (acrylonitrile-co-acrylic acid) membrane containing MWCNTs, as well as the promoted electron transfer from hydrogen peroxide to the immobilized catalase through the PANCAA/MWCNTs nanofiber. Reprinted from [209] (reproduced by permission ofWiley-VCH).

It has been shown recently that the selective reductive homo-coupling polymerization of aromatic diisocyanates via one electron transfer promoted by samarium iodide in the presence of hexamethylphosphoramide [PO(NMe2)3] (HMPA) can produce poly(oxamide)s in nearly quantitative yield (Scheme 9). 

J. Yang, N.F. Hu, and J.F. Rusling, Enhanced electron transfer for haemoglobin in poly(ester sulfonic acid) films on pyrolytic graphite electrodes. J. Electroanal. Chem 463, 53-62 (1999). 

It has been recognized that sulfur donors aid the stabilization of Cu(i) in aqueous solution (Patterson Holm, 1975). In a substantial study, the Cu(ii)/Cu(i) potentials and self-exchange electron transfer rate constants have been investigated for a number of copper complexes of cyclic poly-thioether ligands (Rorabacher et al., 1983). In all cases, these macrocycles produced the expected stabilization of the Cu(i) ion in aqueous solution. For a range of macrocyclic S4-donor complexes of type... 

Sabbatini N, Dellonte S, Bonazzi A et al (1986) Photoinduced electron-transfer reactions of poly(pyridine)ruthenium(II) complexes with europium(III/II) cryptates. Inorg Chem 25 1738-1742... 

The electrochemical and spectroscopic data indicates that sites on these polymers can communicate with each other, in the electron transfer sense, on a relatively short time scale and without the formation of stable mixed valence clusters. Electronic tranport via hopping or tunnelling and modulated by means of neighboring molecular group collisions would be consistent with these requirements. The relative molecular nonspecificity of this mechanism suggests that other polymeric materials would show similar effects and this has been seen for thin films of poly — (vinylferrocene) and poly — (nitrostyrene). 

An effective and mild electrocatalytic procedure for the deprotection of the 1,3-dithiane group of (68), giving the ketone (67), has been developed by using a small amount of tris(/ -tolyl)amine as a homogeneous electron-transfer catalyst (Scheme 26) [86]. The scope and limitations are discussed in detail [87]. The method can be applied also for oxidative removal of the 4-methoxybenzyl thioether protecting group from poly-cystinyl peptides [88]. 

---