Bistability in molecular donor—acceptor complexes

Abstract

This work examines the possibility of bistability in donor—acceptor complexes, i.e. of a near degeneracy between a neutral DA and an ionic D +A − potential well, which differ by both the electronic states and the intramolecular conformations. It is assumed that the inter-system distance R AD and the relative orientation of D and A may be fixed by appropriate rigid chemical bridges. It seems rather difficult to conceive such molecular bistable designs from closed-shell donors and acceptors, while a donor free radical and a closed-shell acceptor can generate a low ionic state. One then finds a range of R AD distances for which the system is bistable. The problem of the switching from one state to the other by the application of an electric field is also discussed.