Polypyrrole-viologen

Figure 12. (A) The amperometric response of (a) a polypyrrole-viologen-nitrate reductase electrode and (b) an identical electrode constructed without the enzyme, in response to injections (a) increasing the nitrate concentration by 3.5 pM, and (y) of buffer. (B) Calibration curves (inset smaller concentration range) for the response to nitrate of a polypyrrole-viologen-nitrate reductase electrode at —0.7 V vs. SCE. Adapted from Ref. [106a with permission.

The catalytic activity of viologen modified polypyrrole electrodes in preparative elK tror luctions has been extended from vicinal to geminal poly-... 

The quaternary groups in viologens can be derivatised to produce compounds capable of chemically bonding to a surface, especially electrode surfaces. These include symmetrical silanes, e.g. (1.93), which can bond to the oxide lattice on the electrode surface, and a viologen with pyrrole side chain (1.94) that undergoes anodic polymerisation to form a film of the viologen bearing polypyrrole on the electrode. Polymeric bipyridilium salts such as (1.95) have also been prepared for use in polymeric electrolytes. ... 

S. Kawabata, H. Yoneyama and H. Tamura, Redox behavior and electrochromic properties of polypyrrole films in aqueous solutions, Bull. Chem. Soc. Jpn., 1984, 57, 2247 P.C. Bookbinder and M.S. Wrighton, Electrochromic polymers covalently anchored to electrode surfaces. Optical and electrochemical properties of a viologen-based polymer./ Electrochem. Soc., 1983,130, 1080. 

The immobilization of an active species into a conducting polymer layer allows one to obtain active electrodes for the reduction of various organic halides. Polypyrrole containing viologen electrodes appear to be active for the reduction of alkyl dibromide [177] or hexachloroacetone [178], Cobalt-bipyridyl-polypyrrole films are active electrodes for the reduction of alkyl chloride [107], The mechanism of this reaction is similar to that observed in the homogeneous phase. This confinns one of the major interests of the modified conductive polymer electrodes, i,e. the possibility of performing catalytic reactions with smaller amounts of active catalyst in comparison to homogeneous catalysis, and then to avoid problems related to the separation of products from the solution which contains this catalyst. 

Liu, X., K.G. Neoh, L. Cen, and E.T. Kang. 2004. Enzymatic activity of glucose oxidase covalently wired via viologen to electrically conductive polypyrrole films. Biosens Bioelectron 19 823. 

Cen, L. Neoh, K. G. Kang, F. T. Surface functionalization of polypyrrole film with glucose oxidase and viologen. Biosens. Bioelectwn. 2003, 4, 363-374. 

Havinga, E. E., Van Horssen, L. W., ten Hoeve, W., Wynberg, H., and Meijer, E. W., Self-doped water soluble conducting polymers, Polym. Bull., 18, 277-281 (1987). Bidan, G., Deronzier, A., and Moutet, J. C., Electrochemical coating of an electrode by a polypyrrole film containing the viologen (4,4 -bipyridinium) system, J. Chem. Soc. them. Commun., 1185-1186 (1984). 

The electrochemical deposition of precious metal microparticles into alkylammonium- (1) and pyridinium- (2 and 3) substituted polypyrrole films has also been achieved by Moutet and coworkers [140, 198, 199]. The electrodes coated with those polymers were successfully used for the electrocatalytic hydrogenation of some unsaturated organic compounds in aqueous media. It was demonstrated that the redox-active viologen groups in poly(3) improved markedly the conductivity and the stability of the catalytic films [198]. 

In the latter example and others involving polypyrrole films electroformed from a complex between a transition metal (Ru(II)) and a bi- or terpyridine-substituted pyrrole [201, 202], the electron self-exchange was ensured by either the viologen or Ru(II) units and not by the polymer. As a matter of fact, the PPy matrix was undoped when poly(3) was used for electrocatalytic reduction experiments or overoxidized when the films containing ruthenium(II)-based complexes were involved in oxidation experiments [201, 202]. 

To avoid these phenomena, it is possible to prepare a hybrid gel with a conducting polymer (e.g., a polypyrrole). This gel can be operated with a low voltage of 0.4-1.4 V [45]. With a solution that contains an oxidation-reduction agent like hydroquinone or viologen derivatives the voltage can be reduced to 1.2 V [46]. 

Besides PEDOT other conducting polymers have been used to attach electrochromic dyes such as polypyrrole, polythiophene, poly(cyclopenta-dithiophene), and poly 1.4-bis[2-(3.4-ethylenedioxy)thienyl]benzene peryl-enetetracarboxylic diimides besides viologens as chromophores. The same... 

Martre A, Laguitton-Pasquier H, DenmziCT A, Harriman A (2003) Preparation and properties of a soluble polypyrrole-polypyridyl-ruthenium(II)-viologen dyad. J Phys Chem B 107 2684-2692... 

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