title: Multistate treatments of the electronic coupling in donor-bridge-acceptor systems: insights and caveats from a simple model.
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.
authors.affiliation: Department of Chemistry, Harvey Mudd College , Claremont, California 91711, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Cave
authors.forename: Marshall D
authors.initials: MD
authors.lastname: Newton