Electron transfer photoexcitation combined with

The second type of radical photoinitiators is the so-called bimolecular photoinitiators that consist of a diaryl ketone together with a compound that provides easily abstractable hydrogen atoms. The most common of these photoinitiators consists of benzophenone or a substituted benzophenone in combination with an aliphatic tertiary amine. A proposed mechanism for the formation of radicals by these bimolecular photoinitiators is depicted in Scheme 10. Photoexcitation of benzophenone results in the formation of triplet-state benzophenone that forms a charge transfer complex, 22, with triethanolamine. Formal electron transfer takes place with the subsequent formation of a radical cation-radical anion... 

The above reaction scheme was established by a combination of uv-visible absorption and fluorescence, ir isotopic substitution, esr and kinetic measurements (37). The important point to note here is that in 02 rich Xe matrices, ground state Cu(2Sj/2) cannot avoid reactive encounters with 02 to form Cu(02)2 and Cu(02) dioxygen complexes,whereas it is proposed that the formation of CuO, Cu(03) and 03 in dilute 02/Xe matrices arises from the reaction of a long lived mobile excited state Cu(2D) with 02. On the other hand the reactions of photoexcited Ag(2P) with 02 are different (37), electron transfer being favoured to form Ag 02. ... 

If, on the one hand, preparative approaches have recently reached the level found in nature, the properties and applications of materials based on combinations of metal complexes and metals with macromolecules seem, on the other hand, to be still under development. The future offers the prospect of providing new materials with unique and unexpected features. Chapters 9 through 14 give insight in the most developed fields of binding of small molecules, sensors, catalysis and electron transfer, including processes induced by photoexcited states. 

The photocatalytic properties and electron/photon-induced processes related to natural systems treated in Chapters 13 and 14 have been researched in depth. Different single fundamental multi-electron catalytic processes and photoexcited state electron-transfer reactions, both in polymer matrixes, are described in relation to photosynthesis (Section 13.2). It is now necessary to combine these reactions step by step to produce artificial photosynthetic systems. Some photoinduced energy-transfer processes (photooxidations) have now reached the level of practical application for wastewater cleaning (Section 13.4) and should be extended to other reactions induced by irradiation with visible light. 

Phthalimides react with KOAc under photochemical conditions to undergo decarhoxylative addition of a methyl group (eq 43). These reactions proceed through single electron transfer from the carboxylate ion to the photoexcited phthalimide to generate the corresponding radical anion and the acetate radical that loses CO2 and releases the methyl radical that eventually combines with the phthalimide radical anion. 

Thus, the long lived photoexcitations of the oligothiophenes in highly polar solvents are a combination of neutral triplet excitations and charged excitations, where the neutral triplets still dominate. The interaction of oligothiophenes with C o in polar solvents such as ODCB is photoinduced electron transfer from the excited state of the oligomers onto C o (or hole transfer from excited C6o onto the oligomer). 

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