## LSU Historical Dissertations and Theses

1997

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Philip W. West

#### Abstract

The research presented in this dissertation generally involves aspects of molecular spectroscopy and contains two areas of focus. In the first section, the influences of organized media on the excited-state phenomena of intramolecular proton transfer (ESIPT) and photoisomerization have been investigated. Specifically, the photochemical properties of the novel ESIPT molecule 10-hydroxybenzo(h) quinoline (HBQ), as well as 2-(2$\sp\prime$-hydroxyphenyl)benzazoles (HBAs), have been examined in the presence of cyclodextrins (CDs) and micelles using absorbance, steady-state, and time-resolved emission spectroscopies. Additionally, the influence of cyclodextrins upon the photoisomerization of trans-stilbene (TS) has been studied. Results from spectroscopic studies of HBQ and HBAs in organized media suggest reduced rates of radiationless transition of the excited tautomer states of these molecules. HBQ exhibits enhanced tautomer emission in both cyclodextrins and micelles through the formation of 1:1 complexes. Moreover, interaction of HBAs with CDs (e.g., $\beta$- and methylated $\beta$-CD$\rm\sb{x})$ enhance both the ground and excited electronic state (S$\sb0$ and S$\sb1,$ respectively) intermolecular proton transfer (PT) of two of the HBAs (2-(2$\sp\prime$-hydroxyphenyl) benzimidazole and -benzothiazole), while enhancing the S$\sb0$ state intermolecular PT and reducing the S$\sb1$ state PT rate of 2-(2$\sp\prime$-hydroxyphenyl)-benzoxazole. Data obtained from induced circular dichroism and time-resolved emission studies are used to further suggest differences in the structural orientation of these molecules in the S$\sb0$ and S$\sb1$ states, and the existence of zwitterionic tautomer species of HBAs, respectively. In the case of trans-stilbene, a dual fluorescence is observed for the molecule in ternary aqueous solutions of $\gamma$-cyclodextrin ($\gamma$-CD$\rm\sb{x}).$ The ternary component (cyclohexane or toluene) plays an active role in increasing the excimer emission of the molecule through the formation of ternary complexes that restrict the photoisomerization of trans-stilbene in the cyclodextrin cavity. The results from time-resolved emission and anisotropy studies further support the formation of extended linear aggregates of trans-stilbene:$\gamma$-CD$\rm\sb{x}$ with these components. The second section of this dissertation concerns the development of analytical assays for modified low-density lipoproteins (LDLs) using multidimensional stopped-flow (SF) spectrophotometric methods. Specifically, SF assays for lipid peroxides have been developed using triiodide and indigo carmine dye as chromophores. The data obtained are used to assess the suitability of these assays for modified LDLs.

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