Effects of High Pressure on the Luminescence of Intramolecular Charge Transfer Compounds
Rollinson, Alonzo Milton
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Permalink
https://hdl.handle.net/2142/66641
Description
Title
Effects of High Pressure on the Luminescence of Intramolecular Charge Transfer Compounds
Author(s)
Rollinson, Alonzo Milton
Issue Date
1980
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
Language
eng
Abstract
The effects of high pressure on the luminescence properties of four organic intramolecular charge transfer compounds were investigated. The compounds were studied in a wide range of liquid and polymeric environments, and for one of the compounds, the effect of the chemical substitution was also examined. In general, an increase of pressure affects the luminescence in a way similar to an increase of solvent polarity: luminescence is shifted to lower energy. A single configuration coordinate model was used to interpret the luminescence in terms of excited state interactions.
Three of the compounds exhibited only florescence: p-(9-anthryl)-dimethylaniline (ADMA), 6-propionyl-2-dimethylaminonaphthalene (PRODAN) and 1-anilino-8-naphthalenesulfonate (ANS). Fluorescence from the first two compounds in nonpolar media is attributed to an excited state relatively unaffected by the charge transfer process. In polar media, fluorescence is believed to originate from another excited state that possesses considerable charge transfer character, and whose energy is strongly influenced by solvent polarity. At high pressure, an apparent fluoresence shift to higher energy was observed in viscous alcohols. This was explained as the introduction of fluorescence from the energetically higher lying non-charge transfer excited state. This explanation is supported by the dual fluorescence decay observed from ADMA coincident with the sign reversal in fluorescence peak shift. Three excited states are believed to affect ANS fluorescence, two of them with charge transfer character. The model describing the excited states of ADMA and PRODAN is consistent with ANS fluorescence in every media except glycerol, where the viscosity and large solvent polarizability are believed to induce an excited state molecular conformation different from those in other media.
The fourth compound, nitroaniline, was studied in its three isomeric forms, with and without N-methylation. In addition to affecting the phosphorescence and fluorescence of p-nitroaniline, pressure studies indicate that n(pi)* singlet and triplet states figure prominently in the radiative and nonradiative processes of o-nitroaniline and m-nitroaniline, as well.
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