Reprinted from the Canadian Journal of Chemistry, 77, 1356-1365 (1999).
© 1999, National Research Council of Canada.
L.T. Okano, R. Ovans, V. Zunic, J.N. Moorthy and C. Bohne*
Contribution from the Departyment of Chemistry, University of Victoris, Victoria, British Columbia, V8W 3V6.
Abstract: The photodecomposition of a-guaiacoxyacetoveratrone (GAV) in homogeneous solvents and in aqueous cyclodextrin solutions was studied by following the fluorescence emission of the photoproducts formed. The same qualitative behavior as previously observed for the photodegradation quantum yield measurements was reproduced in the fluorescence studies in dry or wet methanol and acetonitrile. The yield for GAV photodegradation in water is smaller than in the organic solvents. Complexation of GAV to b- and g-cyclodextrins leads to an increase in the photodecomposition yield, especially during the early part of the photodecomposition kinetics. The transients formed in the photolysis of GAV in water are similar to those observed in acetonitrile and the lifetime of triplet GAV in water is 130 ns. In addition, solvated electrons were formed when GAV was photolyzed in water. Complexation of GAV to cyclodextrins leads to an increase in the triplet yield compared to the radical yield and a moderate shortening of the triplet lifetime.