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

Photophysical studies of naphthalene confirm that aromatic molecules tend t o aggregate within cation exchanged Y zeolites. Ground-state aggregation is traced to the presence of cation-aromatic pi-interaction. Solvents that ca n coordinate to the cation "turn off' the cation-aromatic interaction, and consequently aggregation does not occur in zeolites that are impregnated wi th the above solvents. The solvent that exhibits a maximum in such an effec t is water. MP2 calculations on cation-benzene dimer indicate that cation-p i-interaction results in stabilization of the pi-stacked benzene dimer. Res ults of MP2 calculations are consistent with the formation of ground-state pi-stacked aggregates of naphthalene molecules within Y zeolites.