Cation-π-interaction promoted aggregation of aromatic molecules and energy transfer within Y zeolites

Photophysical studies of naphthalene confirm that aromatic molecules tend to aggregate within cation exchanged Y zeolites. Ground-state aggregation is traced to the presence of cation-aromatic π-interaction. Solvents that can coordinate to the cation 'turn off' the cation-aromatic interaction, and consequently aggregation does not occur in zeolites that are impregnated with the above solvents. The solvent that exhibits a maximum in such an effect is water. MP2 calculations on cation-benzene dimer indicate that cation - π-interaction results in stabilization of the π-stacked benzene dimer. Results of MP2 calculations are consistent with the formation of ground-state π-stacked aggregates of naphthalene molecules within Y zeolites.