Porphyrin electrode films prepared by electrooxidation of metalloprotoporphyrins

Abstract

Electrooxidation in organic solvents of the dimethyl esters of several metalloprotoporphyrins (PP) (NinPP, ZnnPP, ConPP, (FemPP)Cl, (FemPP)20, and (CrmPP)20) leads to the deposition of thick (~1 000 monolayer equivalents), electroactive porphyrin films, which have been characterized by cyclic voltammetry and absorption spectroscopy on transparent Sn02 electrodes.The films are stable toward organic solvents and aqueous acids and bases, but are removed by treatment with hot concentrated acids. The resonance Raman spectrum of the NiPP film indicates that one of the two vinyl groups is saturated on most of the porphyrin units. Deposition continues for some minutes after the current is interrupted. This evidence is consistent with a mechanism involving electroinitiated cationic vinyl polymerization. No film is formed if the metal, rather than the ring, is oxidized. Thus the first oxidation step of ConPP, to [ComPP]+, does not support film formation (although the potential is as high as for ring oxidation in ZnPP), but the second step, to [Co111??•]2"1", does. Lack of film formation for (MnnlPP)Cl and (CrIVPP)0 suggests metal, rather than ring oxidation, to MnIV and Crv. However, (CrPP)20 oxidation does produce a film, suggesting ring oxidation, analogous to (FePP)20, which also produces a film. However, while (CrPP)20 is incorporated intact into the film, the (FePP)20 film contains monomer units. Incorporation of other metal ions can be accomplished by soaking a ZnPP-coated electrode in H2S04 followed by contact with a solution of the metal dihalide in refluxing DMF. The porphyrin sites are accessible to small ions, as shown by chloride coordination of ZnPP film upon soaking in chloride solution.

Monomeric and Polymeric Tetra-aminophthalocyanatocobalt(II) Modified Electrodes: Electrocatalytic Reduction of Oxygen

“…Increasing the time from 2 to 10 min in 1 ϫ 10 -4 M Co(II)TAPc/DMF solution does not show any significant resolution of these redox couples but the residual current increases with increasing thickness of the film. This behaviour has been observed for related polymerization processes with, for example, metalloporphyrins [45,46].…”

ELECTRODES MODIFIED BY Π STACKING OF METALLIC PHTHALOCYANINES AND ITS ELECTROCATALYTIC ACTIVITY ON NITRITE OXIDATION

“…By using Equation 2, the number of electrons (Table 2) is obtained, giving a number close to 2, which implies that the number of transferred electrons is 2. This value was the same for all systems, as Table 2 shows, being coherent with all investigations based on nitrite oxidation [19,25], where NO 3 -, would be the main product of this reaction [26,27].…”

Formation of poly-Phenylporphyrin Film Activated by Superoxide Anion Radical

“…[3,16,36] Схема 1 иллюстрирует рекомбинацию радикалов порфирина, приводящую к об-разованию димера H 2 T(р-NH 2 Ph)P (начальная стадия образования поли-H 2 T(р-NH 2 Ph)P пленки).…”

“…Примени-тельно к макрогетероциклическим соединениям процесс электрополимеризации был первоначально разработан для винил-замещенных порфиринов, [3] позднее [4][5][6][7][8][9] по-казана применимость электрохимического метода для получения пленок (гидрокси-, амино-, пиррол-, тиофен-и др.) замещенных порфиринов.…”