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Polyene photochemistry : solvent controlled state ordering

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Item Summary

Title: Polyene photochemistry : solvent controlled state ordering
Authors: Fenstemacher, Roland John
Keywords: Photochemistry
Retinonitrile
Issue Date: 1982
Abstract: Four nitrile retinoids were synthesized: 1,1-didemethyl- β-ionylidenacetonitrile; 5,6,7,8,9, 10,11,12-octahydroretinonitrile; 5,6,7,8-tetrahydroretinonitrile; and retinonitrile. These four compounds were dissolved in either hexane, ethanol, or acetonitrile and irradiated. Both initial photoproducts and photostationary states showed retinonitrile has solvent dependent photobehavior. 11-cis-Retinonitrile, like 11-cis-retinal, only appears after retinonitrile is irradiated in either acetonitrile or ethanol. The other three compounds, 1, 1-didemethyl- β-ionylidenacetonitrile, 5,6,7,8,9,10,11,12-octahydroretinonitrile, and 5,6,7,8-tetrahydroretinonitrile, showed no such solvent dependent photobehavior, all their photoproducts were present in all irradiation solvents. From the high energy of the nitrile ˡ(n,π*) transition, it follows solvent dependence must be a native polyene trait. Of the four compounds only the longest, retinonitrile, has solvent dependent photobehavior. These data suggest that a pair of ˡ(π , π*) states, a "covalent" 2ˡAgˉ state and an "ionic" 1ˡBu+ state, are responsible for this solvent effect and length requirement. The "ionic" 1ˡBu+ state is stabilized by polar solvents to become the lowest excited state and controls retinonitrile photochemis in ethanol and acetonitrile. This 1ˡBu+ state is not stabilized by non-polar solvents, and the "covalent" 2ˡAg- state remains the lowest excited state and controls retinonitrile photochemistry in hexane. The length requirement comes from the 2ˡAg- state not being stabilized by conjugation enough to be significantly below the 1ˡBu+ state until a "hexaene", retinonitrile. These results may generalize to other retinoids/ polyenes.
Description: Thesis (Ph. D.)--University of Hawaii at Manoa, 1982.
Bibliography: leaves [130]-138.
Microfiche.
ix, 138 leaves, bound ill. 29 cm
URI/DOI: http://hdl.handle.net/10125/9492
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections:Ph.D. - Chemistry



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