Photochemistry of hydrocarbon{center_dot}O{sub 2} complexes in a zeolite matrix cage
- Lawrence Berkeley National Lab., CA (United States)
Molecular-size cages of zeolites offer an opportunity for conducting controlled bimolecular photochemistry at ambient temperature. Collisional complexes can be prepared at high concentration in this matrix environment. Irradiation of the reactants in a state of collision affords direct access to low-energy reaction pathways by single photon excitation. We have found that small alkenes, alkanes, and aromatics, loaded together with O{sub 2} from the gas phase into alkali or alkaline earth exchanged zeolite Y exhibit a hydrocarbon{sm_bullet}O{sub 2} charge-transfer absorption that extends into the visible region. This is due to a very strong stabilization of the excited hydrocarbon{sm_bullet}O{sub 2} charge-transfer state by the high electrostatic fields of the zeolite cage (1.5 to 3 eV). The fields have been measured by the induced infrared fundamental of O{sub 2} and N{sub 2} (NaY, 0.4 V{Angstrom}{sup -1}; BaY, 0.9 V{Angstrom}{sup -1}). Irradiation of these hydrocarbon-oxygen bands with visible light resulted in conversion of olefins, alkanes, and alkyl substituted benzenes to corresponding aldehydes or ketones at very high selectivity. We have developed nanosecond (step scan) FT-infrared spectroscopy (4000-850 cm{sup -1}, 10 nsec resolution) as a tool for detailed mechanistic studies of chemical reactions in zeolites. First results of time-resolved FT-infrared experiments in these matrices will be presented.
- OSTI ID:
- 370690
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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