A theoretical study of the structure and energetics of stacked dimers of polycyclic aromatic hydrocarbons. Application of INDO 1/S method to singlet excimers of naphthalene and phenanthrene

We show here that, with the incorporation of intermolecular distance dependence of π-σ interactions, the INDO 1/S method promises to be a very useful tool for investigating the structure and energetics of singlet excimers of polycyclic aromatic hydrocarbons. Application of the method to naphthalene yields binding energies and vertical transition energies (in absorption and in emission) of the singlet excimer which are in good agreement with experiment. The method also provides a possible explanation for the failure of phenanthrene to exhibit excimer fluorescence or the self-quenching of the monomer fluorescence.