J Phys Chem A. 2014 Sep 04;118(35):7221-34. doi: 10.1021/jp408913k. Epub 2013 Dec 10.

Multistate treatments of the electronic coupling in donor-bridge-acceptor systems: insights and caveats from a simple model.

The journal of physical chemistry. A

Robert J Cave, Marshall D Newton

PMID: 24266545 DOI: 10.1021/jp408913k

Abstract

We use a simple one-dimensional delta function electronic structure model (dfm) to investigate the results of a pair of multistate diabatization techniques (i.e., based on n states, with n ≥ 2) for linear DBA and DBBA (donor-bridge-acceptor) electron-transfer systems. In particular, we focus on the physical meaning of the couplings obtained from multistate methods and their relationship to two-state (n = 2) coupling elements. On the basis of the simple dfm approach, which allows exact as well as finite basis set treatment and has no many-electron effects, we conclude that for orthogonal diabatic states, it is difficult to assign clear physical significance to multistate matrix elements for coupling beyond nearest-neighbor contacts. The implications of these results for more complex multistate many-electron treatments are discussed. It is emphasized that physically meaningful coupling elements must involve states that are orthogonal, either explicitly or implicitly.

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• Journal Article