Redox photoredox reaction

The photovoltaic effect is initiated by light absorption in the electrode material. This is practically important only with semiconductor electrodes, where the photogenerated, excited electrons or holes may, under certain conditions, react with electrolyte redox systems. The photoredox reaction at the illuminated semiconductor thus drives the complementary (dark) reaction at the counterelectrode, which again may (but need not) regenerate the reactant consumed at the photoelectrode. The regenerative mode of operation is, according to the IUPAC recommendation, denoted as photovoltaic cell and the second one as photoelectrolytic cell . Alternative classification and terms will be discussed below. 

The photogalvanic effects are initiated by a homogeneous photoredox reaction of an electrolyte redox system with a suitable photoexcited organic or organometallic substance (dye), S. The photon absorption produces a short-lived, electronically excited dye molecule, S ... 

The solid state and the surface chemistry of some of the solid Fe-phases impart to these oxides and sulfides the ability to catalyze redox reactions. Surface complexes and the solid phases themselves acting as semiconductors can participate in photoredox reactions, where light energy is used to drive a thermodynamically unfavorable reaction (heterogeneous photosynthesis) or to catalyze a thermodynamically favorable reaction (heterogeneous photocatalysis). 

An Aside Redox Potentials Involved in Photoredox Reactions... 

A photoredox reaction is a redox reaction that occurs after electronic excitation of one or several reaction partners. A representative example is given by the charge transfer process that occurs as a consequence of light absorption by a metal-ligand complex. The light absorption promotes an electron from an occupied orbital of the ligand to an unoccupied orbital of the metal ion. Photo-... 

Sulzberger B (1990) Photoredox reactions at hydrous metal oxide surfaces A surface coordination chemistry approach. In Aquatic Chemical Kinetics. Stumm W (ed) p 401-430. New York Wiley Sulzberger B, Siffert C, Stumm W (1988) Surface coordination chemistry and redox processes— Photoinduced iron (III) oxide dissolution. Chimia 42 257-261 Swap R, Garstang M, Greco S, Talbot R, Kallberg P (1992) Saharan dust in the Amazon basin. Tellus B 44 133-149... 

The most common application of surfactants is as solubilising agents for a wide variety of solutes which are othewise insoluble in water. In the case of the redox pair D and A, if the hydrophobicity of either the donor or the acceptor is high, it provides an inherent selectivity in the solubilisation. With one of the reactants solubilised in an ionic micelle and the other randomly dispersed in the bulk water, the photoredox reaction is subject to strong electrostatic effects and in some cases also changes in the dimensionality of the... 

Consideration of the nature of the LMCT transitions, redox energetics, and photoredox behaviour of transition-metal ammine complexes has allowed Endicott and co-workers18 to propose new models for the potential energy surfaces describing their photoredox reactions. These models have been used to discuss the differences in photoreactivity of [Co(NH3)5Br]2+ and [Co(NH3)5-N03]2+.21 These differences are ascribed to (i) more Co-radical bonding in the... 

Topics which have formed the subjects of reviews this year include excited state chemistry within zeolites, photoredox reactions in organic synthesis, selectivity control in one-electron reduction, the photochemistry of fullerenes, photochemical P-450 oxygenation of cyclohexene with water sensitized by dihydroxy-coordinated (tetraphenylporphyrinato)antimony(V) hexafluorophosphate, bio-mimetic radical polycyclisations of isoprenoid polyalkenes initiated by photo-induced electron transfer, photoinduced electron transfer involving C o/CjoJ comparisons between the photoinduced electron transfer reactions of 50 and aromatic carbonyl compounds, recent advances in the chemistry of pyrrolidino-fullerenes, ° photoinduced electron transfer in donor-linked fullerenes," supra-molecular model systems,and within dendrimer architecture,photoinduced electron transfer reactions of homoquinones, amines, and azo compounds, photoinduced reactions of five-membered monoheterocyclic compounds of the indigo group, photochemical and polymerisation reactions in solid Qo, photo- and redox-active [2]rotaxanes and [2]catenanes, ° reactions of sulfides and sulfenic acid derivatives with 02( Ag), photoprocesses of sulfoxides and related compounds, semiconductor photocatalysts,chemical fixation and photoreduction of carbon dioxide by metal phthalocyanines, and multiporphyrins as photosynthetic models. 

A redox reaction between an excited state and suitable reagents can be described like a normal redox reaction as an electron transfer between an occupied energy level and a vacant one. The principle of a photoredox reaction is shown in Fig. 1.3 for a homogeneous system using an energy level scheme for the excited molecule and the potential reaction partners. In the excited state one electron is transferred to a higher electronic level which was previously vacant... 

The energy conversion process contains two photoredox reactions coupled in series by an electron transfer chain. The energy correlations in this series of redox reactions are shown in Fig. 1.9. 

Schematics of a System Based on Photoredox Reactions and Redox Catalysis...

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