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Date of Award

1994

Document Type

Dissertation - Pacific Access Restricted

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Advisor

Silvio Rodriguez

First Committee Member

James W. Blankenship

Second Committee Member

Richard P. Dodge

Third Committee Member

Michael J. Minch

Fourth Committee Member

Paul H. Gros

Fifth Committee Member

Patrick R. Jones

Abstract

Electronic excitation energy transfer from coumarins to xanthene dyes in different media has been investigated. Nonradiative energy transfer between coumarin 1 (d) and fluorescein (a), in 95% ethanol and in n-octanol takes place with critical transfer distances: 48.4 A (d-a) and 21.0 A (d-d) in 95% ethanol, and 46.4 A (d-a) and 25.4 A (d-d) in 1-octanol. The rate constants of nonradiative energy transfer and energy migration in these two solvents were compared with the rates of diffusion. Energy transfer in the three-component system coumarin 1/fluorescein/rhodamine B, was studied. The critical transfer distances between each two of the three components were: 48.4 A for coumarin 1/fluorescein; 42.2 A for coumarin 1/rhodamine B; and 65.5 A for fluorescein rhodamine B respectively. The quantitative description of this three component system indicates that, using our modified correction factors, the experimental data coincided satisfactorily with Kusba-Bojarski general equations of multi-component luminescence system. Nonradiative energy transfer between coumarin 6 and rhodamine 3B in poly-(methyl methacrylate) was studied. The fluorescence quantum yields of coumarin 6 in the monomer and polymer were measured to be 1.00 and 0.94 respectively. The calculated critical transfer distances were: 50.0 A (d-a) and 38.9 A (d-d) in the monomer; and 47.7 A (d-a) and 38.2 A (d-d) in the polymer. Unexpected high energy transfer efficiency was observed in the polymer. Environmental effects on the fluorescence of the fluorophore and the mechanism of energy transfer in fluid and rigid solutions were discussed. Fluorescence quantum yields of coumarin 1 in various alcohols were measured to be: 0.573 in 95% ethanol; 0.688 in ethanol; 0.826 in n-propanol; 0.814 in n-butanol; 0.818 in n-pentanol; 0.912 in n-hexanol; 0.846 in n-heptanol; 0.869 in n-octanol; 0.876 in n-nonanol and 0.882 in n-decanol. The fluorescence lifetimes of coumarin 1 in these alcohols, were calculated to be: 2.23; 3.20; 3.67; 3.42; 3.76; 3.47; 3.35; 3.88; 3.64; and 3.57 ns respectively. Solvent effects on the quantum yields were discussed.

Pages

282

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