- Collection:
- Atlanta University and Clark Atlanta University Theses and Dissertations
- Title:
- Synthesis and characterization of flourescent imidazoles for non-linear optical applications, 2007
- Creator:
- Elliott, Adrian A.
- Date of Original:
- 2007-07-01
- Subject:
- Degrees, Academic
Dissertations, Academic - Location:
- United States, Georgia, Fulton County, Atlanta, 33.749, -84.38798
- Medium:
- theses
dissertations - Type:
- Text
- Format:
- application/pdf
- Description:
- In this work, we have synthesized a series of aromatic substituted imidazoles and studied their photochemical properties ( UV-Vis and fluorescence) in varying solvents. The imidazole based chromophores were substituted in 2-position by phenyl, naphtyl, anthracyl, phenantryl, and pyrenyl groups (noted R). Furthermore, the imidazole ring was substituted in 4- and 5-positions by phenyl, p- tolyl and p-methoxyphenyl to study the electronic effect of the groups in para position-namely, hydrogen, methyl, and methoxyl (noted R). Upon the introduction of more bulky and conjugated groups in 2-position, the geometry of the overall molecule is dramatically altered. The phenyl group is co-planar to the imidazole group but the larger anthracyl group is twisted at a 53 dihedral angle relative to the imidazole ringto minimize steric hindrance. The resulting change in conjugation within the molecule and the polarity-induced interactions from solvent to solute affect the photochemical behaviors of these molecules. Indeed, the UV-Vis profile of the group in 2-position dominates with increased dihedral angle (decrease conjugation). In fluorescence, both the R and Rgroups influenced the maxima of the excited and emitted wavelengths. The maxima were dependent upon the solvents polarities and their hydrogen bonding abilities. Although the solvent effects were important for both stoke shift and quantum yield they varied from molecule to molecule. It was found that with higher dihedral angle the solvent effect on stoke shift is larger. The relative quantum efficiencies were also solvent-dependent and generally high in this study. In fairly apolar, aprotic solvents such as toluene, relative quantum efficiencies range from 0.94 to 1.00. In contrast, with solvents such as dioxane and chloroform major quenching was observed. A direct correlation of solvent induced fluorescence shift with solvent parameters such as 7r*, a, (3, and ET(30) was not evident because of inter-dependency of factors such as molecule structure and degree of conjugation.
Date of award: 7/1/2007
Degree type: thesis
Degree name: Master of Science (MS)
Granting institution: Clark Atlanta University
Department: Department of Chemistry - Metadata URL:
- http://hdl.handle.net/20.500.12322/cau.td:2007_elliott_adrian_a
- Holding Institution:
- Atlanta University Center Robert W. Woodruff Library
- Rights:
-
