A fresh look at excitonically coupled chromophores from a Jahn-Teller perspective

A symmetric carbon monoxide dimer (CO dimer) serves as one of the simplest possible models to investigate exciton localization in excitonically coupled chromophores with high-level quantum chemical methods. It is demonstrated that distance dependent excitonic coupling tunes the energy splitting of vibronically coupled dimer states. With decreasing excitonic coupling strength a pseudo Jahn-Teller distortion emerges resulting in exciton localization on one of both monomers. Connection between excitonic coupling and Jahn-Teller theory is made. Furthermore it is shown that an external electric field can direct the localization of the exciton towards one particular monomer via a charge transfer mediated localization mechanism. (C) 2010 Elsevier B.V. All rights reserved.