Formation of a molecular exciplex and structure of van der Waals complexes of the naphthalene-triethylamine system

Investigations of the potential energy surfaces of the ground and excited states of the electron donor-acceptor (EDA) system of naphthalene with triethylamine have revealed the existence of different isomeric forms of the system. These isomers, characterized by different relative orientations of the donor and acceptor molecules, are distinctly different in their ability to form a molecular exciplex. These results are used for an explanation of the fluorescence excitation and emission observed under conditions of jet-cooled molecular supersonic beams. They also explain the activated as well as the barrierless character of the exciplex formation reaction in this and similar EDA systems.