Porphyrins chemically modified

The indicated formal potential E° n of the corresponding monomer (-1.17V) in solution is very near that of the surface film (-1.13V vs. SSCE). That formal potentials of surface films on chemically modified electrodes are near those of their corresponding dissolved monomers (13,18) is actually a common, and quite useful, observation. In the present case, it demonstrates that the electronic structures of the porphyrin rings embedded in the polymer film are not seriously perturbed from that of the monomer. 

One such reaction that has been studied is the electrocatalytic reduction of oxygen directly to water.25,27 The electrocatalysts for this process are often based on metal porphyrins and phthalo-cyanins. Thus a graphite electrode whose surface was modified by the irreversible adsorption of a cofacial dicobalt porphyrin dimer was able to reduce oxygen under conditions where the reduction did not occur on the bare electrode itself. Similarly, a catalytic chemically modified electrode for the oxidation of chloride to chlorine has been prepared28 where the active catalyst was reported to be a ruthenium dimer, [(bipy)2(OH)RulvORuvO(bipy)2]4+, which was reduced to the corresponding [Rum-RuIV] dimer during the reaction. 

Hayashi T, Takimura T, Ogoshi H (1995) Photoinduced singlet electron transfer in a complex formed from zinc myoglobin and methyl viologen artificial recognition by a chemically modified porphyrin. J Am Chem Soc 117 11606-11607... 

Double chemically modified Hb with thermostability, and it was able to oxidize synthetic porphyrins and asphaltenes The double chemically modified Hb showed [80]... 

Some papers have appeared that deal with the use of electrodes whose surfaces are modified with materials suitable for the catalytic reduction of halogenated organic compounds. Kerr and coworkers [408] employed a platinum electrode coated with poly-/7-nitrostyrene for the catalytic reduction of l,2-dibromo-l,2-diphenylethane. Catalytic reduction of 1,2-dibromo-l,2-diphenylethane, 1,2-dibromophenylethane, and 1,2-dibromopropane has been achieved with an electrode coated with covalently immobilized cobalt(II) or copper(II) tetraphenylporphyrin [409]. Carbon electrodes modified with /nc50-tetra(/7-aminophenyl)porphyrinatoiron(III) can be used for the catalytic reduction of benzyl bromide, triphenylmethyl bromide, and hexachloroethane when the surface-bound porphyrin is in the Fe(T) state [410]. Metal phthalocyanine-containing films on pyrolytic graphite have been utilized for the catalytic reduction of P anj -1,2-dibromocyclohexane and trichloroacetic acid [411], and copper and nickel phthalocyanines adsorbed onto carbon promote the catalytic reduction of 1,2-dibromobutane, n-<7/ 5-l,2-dibromocyclohexane, and trichloroacetic acid in bicontinuous microemulsions [412]. When carbon electrodes coated with anodically polymerized films of nickel(Il) salen are cathodically polarized to generate nickel(I) sites, it is possible to carry out the catalytic reduction of iodoethane and 2-iodopropane [29] and the reductive intramolecular cyclizations of 1,3-dibromopropane and of 1,4-dibromo- and 1,4-diiodobutane [413]. A volume edited by Murray [414] contains a valuable set of review chapters by experts in the field of chemically modified electrodes. 

Bedioui, R, S. Trevin, V. Albin, M.G.G. Villegas, and J. Devynck (1997). Design and characterization of chemically modified electrodes with iron(III) porphyrinic-based polymers Study of their reactivity toward nitrites and nitric oxide in aqueous solution. Anal. Chim. Acta 341,177-185. 

In 1988, a pioneering work dealing with electrode characteristics of an immobilized enzyme chemically modified electrode based on bilayer-film coating for amperometric determination of glucose was reported. In this work, a substrate was coated with two kinds of polymeric films in a bilayer state, that is, first with the cobalt tetrakis(o-aminophenyl)porphyrin polymer film and then with the enzyme film consisting of bovine serum albumin and glucose oxidase that were... 

More recently, hydroxy-substituted cobalt tetraphenylporphyrins, electro-polymerized onto an optically transparent electrode and adapted onto the tip of an optic fibre were used as sensing materials for the development of optic fibres as pH-sensors . The pH values by this chemically modified optic fibre were monitored by spectrophotometric measurement of the Soret band wavelength for the supported porphyrin. 

Modification of the electrode started with academic studies on physical and chemical adsorption, i.e., with the appearance of fundamental researches on adsorption of different species on electrode surfaces, both under polarization and at open circuit potential [3]. The properties of similar chemically modified electrodes , in which the modifier consists of a monolayer of a variety of chemical species with different characteristics, possessing (or not) particular properties, were initially studied in a purely electrochemical context, aimed at the collection of fundamental physico-chemical data. A small group of electrochemists were among those involved in these basic studies, envisioning the perspectives opened by the novel systems. In the first, really fascinating, work with similar monomolecular layers, cobalt porphyrin and phthalocyanine, as well as deliberately synthesized dicobalt face-to-face porphyrins were adsorbed on Pt or C surfaces to catalyze molecular oxygen reduction [4]. However, similar systems were not always used or adequately tested in proper amperometric sensing by researchers more interested in electroanalysis dicobalt face-to-face porphirins still constitute a rare example of tailored materials for selective amperometric detection. 

Other types of planar NO microsensors include Pt microelectrodes chemically modified by electrodeposition of metaUoporphyrin-like nickel(II) complexes. For example, tetrasul-fonated phthalocyanine tetrasodium (NiTSPc) was electrodeposited on the bare electrode surface by repetitive cychc voltammetry (21). Alternatively, electrode functionalization using nickel(4-iV-tetramethyl)pyridyl porphyrin (NiTmPyP) as an electrocatalyst was also carried out by applying multiple pulses in differential pulse amperometry (22). In this case, the electrocatalyst was entrapped in a NO selective polymer network of a negatively charged acrylic acid resin that prevented access by anionic interfering species. 

Lennox JC, Murray RW (1977) Chemically modified electrodes. VI. Binding and reversible, electrochemistry of tetra(aminophenyl)porphyrin on glassy carbon. J Electroanal Chem 78 395 1... 

Lennox JC, Murray RW (1978) Chemically modified electrodes. X. ESCA and AC voltammetry of glassy carbon-bound tetra(aminophenyl)porphyrins. J Am Chem Soc... 

Rocklin RD, Murray RW (1979) Chemically modified carbon electrodes. XVn. metallation of immobilized tetra(aminophenyl)porphyrin with manganese, iron, nickel, copper and zinc and electrochemistry of dr notonated tetraphenylporphyrin. J Electroanal Chem 100 271-282... 

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