Molecular sigma-bridged

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.

UE began with Aviram and Ratner s 1973 proposal for a molecular rectifier this is the third rectification process [79]. An Aviram-Ratner rectifier has donor and acceptor groups in one molecule, separated by an insulating bridge of sigma... 

The 7i-stacked bases of ds DNA might be expected to provide a better medium for bridge-mediated electron transfer than the sigma bonds of proteins or hydrocarbons. It has in fact been proposed by Turro and Barton [18d] that ultrafast photoinduced electron transfer processes involving intercalated donors and acceptors can occur with little or no distance dependence. According to this paradigm, duplex DNA can function as a molecular wire or r-way . 

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