Electron transfer donor-acceptor compounds

Photoinduced electron-transfer reaction of aromatic compounds with amines is one of the most fundamental reactions in the electron-donor-acceptor systems, which was recently reviewed by Lewis [35], Because of the low oxidation potentials of the amines, the photoinduced one-electron transfer from the amines to the excited singlet states of aromatic hydrocarbons ( Aril ) readily occurs to give the radical cations of amines and the radical anions of aromatic compounds even in the less polar solvents. 

Photochemical electron transfer reactions of electron donor-acceptor pairs in polar solvents provide a convenient and effective method for the generation of radical cations which can be trapped by complex metal hydrides. One of the most effective systems is based on irradiation of a solution of substrate, sodium borohydride and 1,4- or 1,3-dicyanobenzene. A range of bi- and poly-cyclic aromatic hydrocarbons has been converted into the dihydro derivatives in this way. An especially important aspect of this route to dihydroaromatic compounds is that it may give access to products which are regioisomeric with the standard Birch reduction products. Thus, o-xylene is converted into the 1,4-dihydro product (229) rather than the normal 3,6-dihydro isomer (228). The m- and p-xylenes are similarly reduced to (230) and (231), respectively. ... 

The electron donor-acceptor (EDA) complex between alkali metals and aromatic hydrocarbons has been studied by many investigators, and it is generally accepted that free radical ions of aromatic compounds are formed by the transfer of an electron, or electrons, from sodium to the aromatic compounds (1). The added electron is not localized on a particular carbon atom, but is distributed over the whole molecule to form an integral part of the delocalized n-electron system. 

See also activated complex adduct charge-transfer COMPLEX ELECTRON-DONOR-ACCEPTOR COMPLEX ENCOUNTER COMPLEX INCLUSION COMPOUND PI (n) ADDUCT SIGMA (o) ADDUCT, TRANSITION STATE. 

Strongly adsorbed aromatic compounds, which cannot be desorbed even at high temperatures, probably involve an electron-donor-acceptor or charge-transfer mechanism. It has been shown that the surface of a carbon is more effectively used if non-electrostatic interactions are the driving force for the adsorption. This condition can be reached by controlling the surface chemistry of carbon, the pH and ionic strength of the solution. 

ELECTRON DONOR-ACCEPTOR INTERACTIONS AND PHOTO-INDUCED ELECTRON TRANSFER OF ORGANOMETALLIC COMPOUNDS... 

The redox properties of Ru(bipy)5 " (ground state and excited state) have been taken advantage of Ru(bipy)3 is able to transfer an electron to a relay (MV, or a rhodium(III) complex or another electron acceptor) whose reduced form reacts with water to yield hydrogen the latter reaction might be accelerated by the presence of a heterogeneous redox catalyst. The ruthenium(II) complex is regenerated in the reaction between Ru(bipy) " and an electron donor D. This compound D is irreversibly converted to an oxidation product. An ideal system would, of course, use H2O as electron donor, with formation of O2. This remains to be done, but model systems for H2O oxidation have also been proposed [20] ... 

Figure C3.2.7. A series of electron transfer model compounds with the donor and acceptor moieties linked by (from top to bottom) (a) a hydrogen bond bridge (b) all sigma-bond bridge (c) partially unsaturated bridge. Studies with these compounds showed that hydrogen bonds can provide efficient donor-acceptor interactions. From Piotrowiak P 1999 Photoinduced electron transfer in molecular systems recent developments Chem. Soc. Rev. 28 143-50.

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