Effect of the Si/Al distribution on the UV–vis spectrum of propene–zeolite system. A theoretical approach

Abstract

Olefins included in zeolite cavities show strong perturbations on their electron excitation energies even undergoing visible light photoxidations. Approximate SCF-NDOL-CIS calculations on propene–zeolite systems show that supramolecular electron distribution of excited states could be responsible for these effects. Energy calculations were made with a semiempirical QM potential whose reliability was tested against ab initio SCF-MO. Statistically weighted Si/Al relationships for zeolite clusters were also explored and modeled for the case of cages with 18 tetrahedra. Si/Al ratio also appears to influence the electronic states of the model system. The photobehavior dependence on molecular environment is clearly reflected in the results.