Possible Anomalous ‘Mono mer Shifts’ of Merocyanine Dyes in their Aggregates- an Analytical Study

Abstract

To investigate the so-called monomer shifts in aggregates of merocyanine dyes that bear a donor-acceptor type chromophore, a simple model has been introduced to describe the electronic structure of such a chromophore. This model can be solved analytically and the obtained solution tells us that the physical quantities relating to the optical properties of the system, i.e., the excitation energy, the transition dipole moment, the static dipole moment at the ground state, and the static dipole moment at the excited state strongly depend on the extent of the bond alternation in the chromophore, which includes seven atomic Pz orbitals. Based on this model, as a consequence, possibility of anomalous monomer shifts in the merocyanine J-aggregates has been demonstrated.