Vinylferrocene redox reactions

The redox reactions for supported BLMs containing vinylferrocene as an electron mediator have been investigated using cyclic voltammetry. The results have shown the following, (i) Ferrocene can be very easily immobilized in the lipid bilayer on the surface of a metallic wire (s-BLM) system. This demonstrates that the s-BLM system offers a novel approach to electrode modification by simple immobilization of compounds within BLM. (ii) Ferrocene in a BLM increases the sensitivity to the potassium ferri/ferrocyanide ion by about two orders of magnitude in comparison to that of the platinum electrode [79]. 

A second type of electroactive polymer film is the redox polymer which contains localized sites that may be oxidized and reduced. Charge is not distributed along the polymer chain but is localized at specific, pendant redox sites. An example of this type of polymer is poly(vinylferrocene) (PVF) which is shown in Figure 2.1 in both the reduced and oxidized forms. Poly(vinylferrocene) undergoes a reversible redox reaction when used with an appropriate electrolyte (such as LiC104 in acetonitrile) and has been used as a model redox polymer system [17-19]. The oxidation process occurs by removal of electrons and the simultaneous insertion of anions from the electrolyte. The Fe centre in the pendant ferrocene group undergoes oxidation. 

Photochemical studies of iron-group metallocene substrates have received much attention, e.g. quenching of excited uranyl ion luminescence, formation of charge-transfer complexes with TCNE, redox reactions of octamethyl-ferrocene and of carboxylate anions of the types FcCOj and Fc(X)COr (X = saturated or unsaturated alkyl chain). Enzyme-catalysed one-electron oxidation of ferrocene derivatives has also been studied. Ferrocene-ferricenium cation redox systems have been incorporated into electrochemical and photo-electrochemical cells, and have found use for catalysis of photo-addition of MeOH to Bu NCO. Inter-valence electron-transfer properties of partially oxidized Fc(C C)nFc ( = 0—2), meso-tetraferrocenylporphyrin, and poly(vinylferrocene) have been assessed. 

Vinylferrocene (22) may be polymerized (Section 57.3.2.2.i) to give a polymer in which the iron(II/III) redox centres are pendant from a carbon backbone. Copolymers have also been formed with styrene61 and acrylonitrile.62 Another approach using a different polymer is illustrated by the covalent binding of poly(methacryl chloride) to Sn02 electrodes followed by attachment of pendant ferrocene centres by reaction of hydroxymethylferrocene.63... 

Homogeneous charge transfer can take place between chemically similar redox species of one redox couple, e.g., Fe3+ and Fe2+ ions in solution or ferrice-nium and ferrocene moieties in poly(vinylferrocene) films, the electron transfer (- electron hopping or electron exchange reaction) can be described in terms of second-order kinetics and according to the - Dahms-Ruff theory [viii-x] it may be coupled to the isothermal diffusion ... 

Cross-metathesis was recognized as a convenient route to introduce various functionalities into organometallic frameworks, initially including ferrocenes. For example, catalyst with a methylideneferrocenyl ligand was prepared by a stoichiometric reaction of vinylferrocene (4-1) with the Schrock catalyst (Scheme 12.21) [3]. Polymers with one ferrocenyl redox-active end group were obtained with this unique initiator. 

This cube was based ou a previous scheme of squares visual approach. Here, the axes x, y and z, respectively, represent coupled electron/proton transfer, solvent transfer and acetic acid coordination. Four equilibrium constants describe the coordination reactions for the four pairs of species on the left and right faces of the cube. The authors interpreted their data on partial redox switching of poly(vinylferrocene) films imder permselective conditions in aqueous perchlorate bathing electrolytes which produce films that reach... 

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