Long range electron transfer across π-conjugated systems: role of electron correlations

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We consider a prototype polyene chain: donor-π(bridge)-acceptor. The distance between the donor and the acceptor is varied by increasing the number of bridged atoms and rate of electron transfer, ket is studied for a series of different donors, D=NH₂, SH, OH, and a fixed acceptor, A=NO₂. We observe a large ket even at a very large D-A separation of 45 Å, unexpected from the well-known and standard theories like the Forster theory. Such a long range electron transfer is due to the strong electron-electron interactions in the bridged orbitals that result in deconfinment of electrons in donor orbitals. Calculations at various levels: semi-empirical and many-body exact, have been performed to accurately account for such correlations.