Effect of Pressure on the Luminescence of 3-Hydroxyflavone, Indole and Rhenium Complexes
Salman, Omar Abdurrahman
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https://hdl.handle.net/2142/69730
Description
Title
Effect of Pressure on the Luminescence of 3-Hydroxyflavone, Indole and Rhenium Complexes
Author(s)
Salman, Omar Abdurrahman
Issue Date
1982
Department of Study
Chemical Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Abstract
The effects of pressure on the luminescence properties of 3-hydroxyflavone, indole and two rhenium metal-complexes were investigated. Several solvents covering a wide range of viscosities and dielectric constants were used. Radiative and nonradiative rates were calculated from steady state emission and lifetime experimental data.
The effects of viscosity and pressure on the excited state tautomerization process of 3-hydroxyflavone were discussed. It was found that in polar media below a viscosity of (TURN) 50 poise, the process is thermodynamically controlled. Beyond that viscosity the process becomes kinetically controlled where the rate of internal conversion between the two excited states is the determining factor. In non-polar solvents, rigidity has no effect on the tautomerization process.
The effects of pressure and freezing on the decay mechanisms of two sets of compounds were investigated: organic compounds and transition-metal complexes. In the first set (indole and 3-hydroxyflavone), the radiative rates correlate well with the low frequency dielectric constant of the solvent. This correlation is clearly demonstrated at the freezing point. The nonradiative rates are controlled by the viscosity of the media. In the second set (tricarbonylchloro-1,10-phenanthrolinerhenium and tricarbonylchloro-4,7-diphenyl-1,10-phenanthrolinerhenium), the radiative rates also show a good correlation with the low frequency dielectric constant. The nonradiative rates are controlled primarily by intramolecular processes. The blue shift in emission peak energy and the change in shape of the ground state potential well as shown by the change in peak halfwidth are the two main factors controlling the nonradiative rates.
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