Long range electron transfer across $\pi$-conjugated systems: role of electron correlations

Abstract

We consider a prototype polyene chain: donor-$\pi$(bridge)-acceptor. The distance between the donor and the acceptor is varied by increasing the number of bridged atoms and rate of electron transfer, k${}_{et}$ is studied for a series of different donors, D=NH${}_2$, SH, OH, and a fixed acceptor, A=NO${}_2$. We observe a large k${}_{et}$ even at a very large D-A separation of $\sim$ 45 $\mathring{A}$, 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.

Accepted in Phys. Rev. B