Exciton states in organized molecular systems: A model for columnar aggregates

A model to describe the collective electronic excited states in organized molecular systems of finite size featuring a columnar aggregate of triaryl pyrylium salt is presented. Calculations are used to evaluate the diagonal and off-diagonal matrix elements of the aggregate Hamiltonian. Diagonalization of the electronic Hamiltonian provides the eigenstates from which the localization properties are calculated. Delocalized states may exist, even at room temperature, due to the very strong coupling among chromophores. Furthermore, the scattering among eigenmodes of the aggregate is studied as an incoherent energy transfer process induced by stochastic coupling to the thermal bath. Time evolution of populations of the eigenstates is numerically calculated and checked against experimental data.