Excitation, electronic single-step transfer

One possible alternative to the complex modular scheme has been proposed by Meyer and co-workers, and is based upon the integration of excitation, electron, and proton transfer in one single concerted step. Instead of conventional PCET, where light excitation precedes a proton and electron transfer event, the authors propose a mechanism based on photo-EPT. This as a concept has been tested for intramolecular charge transfer in hydrogen bonded dyes, but further development is needed before it can be applied to light driven water splitting devices. 

A single-step electron transfer process between an excited molecule and ground-state molecule separated by a variable number of base pairs, DNA-mediated electron transfer. The possible occurrence of wire-like behavior in DNA has generated considerable controversy and the attention of the popular science press [16]. 

Forster Resonance Energy Transfer. This is a single-step, radzafion/css transfer of electronic excitation. This t5zpe of energy transfer depends in part on the distance between the donor and acceptor but can take place over distances of up to 100 A. Efficient Forster transfer also requires a good overlap of the emission spectnun of the donor and the absorption spectrum of the acceptor. 

In this category, a very hot non-Boltzmann IF(B) vibrational distribution is obtained. Examples of such distributions are found in systems where excited species such as metastable electronically-excited N2(A3ZJ) [18] and NF(b E) [16] and vibrationally-excited HF(X 2 ) [19] collide with IF(X). In all cases, the excitation is thought to come from a single step E E or V -> E energy transfer process... 

The single-electron transfer from one excited component to the other component acceptor, as the critical step prior to cycloaddition of photo-induced Diels Alder reactions, has been demonstrated [43] for the reaction of anthracene with maleic anhydride and various maleimides carried out in chloroform under irradiation by a medium-pressure mercury lamp (500 W). The (singlet) excited anthracene ( AN ), generated by the actinic light, is quenched by dienophile... 

Pandey and co-workers have generated arene radical cations by PET from electron-rich aromatic rings [119]. The photoreaction is apparently initiated by single-electron transfer from the excited state of the arene to ground state 1,4-dicyanonaphthalene (DCN) in an aerated aqueous solution of acetonitrile. Intramolecular reaction with nucleophiles leads to anellated products regio-specifically. The author explains the regiospecifidty of the cyclization step from... 

The oxidation of 3,6-dehydrohomoadamantane (52) with NO+BF4, photo-excited tetracyanobenzene, and under anodic conditions has been found to involve a common radical cation intermediate. The study has shown that the activation of propellane cTc-c bonds with strong oxidizing electrophiles occurs by a sequence of single-electron transfer steps. These findings are supported by ab initio computations showing that the isomeric radical cations can equilibrate with low barriers and lead to a common product. ... 

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