Date of Award

6-1974

Document Type

Open Access

Degree Name

Bachelor of Science

Department

Chemistry

Language

English

Abstract

Previous studies have shown that substitution of a single carboxyl group on the anthracene ring produces fluorescent quantum yields (Øf) and Stokes shifts that are highly solvent dependent. The effects of solvents on the spectral properties of anthracene-9, 10-dicarboxylic acid (9, 10-(COOH) 2) which has symmetrically distributed carboxyl groups, was studied. Comparison is made with spectral data for 9-methyl anthroate (9-C00Me) and anthracene-9, 10-dicarboxylic acid (9, 10-(COOH) 2) which has symmetrically distributed carboxyl groups, was studied. Comparison is made with spectral data for 9-methyl anthroate (9-COOMe) and anthracene-9-carboxylix acid (9-COOH). The absorption and fluorescence spectra of the unprotonated forms of 9-COOH and 9, 10-(COOH) 2 are anthracene-like and have the same Stokes shift within experimental error. For the pronated forms the absorption spectra resemble that of anthracene, however, the fluorescene spectra are broad, structureless and highly red shifted. The Stokes shift of the protonated from of 9-COOH is larger than that of the protonated form of 9, 10-(COOH) 2, because the smaller dipole moment of the latter allows less solute-solvent interaction. The Øf values for 9-COOMe and 9-COOH are the same within experimental error for all solvents, and cover a large range between protic and aprotic solvents. The Øf values for 9, 10-(COOH) 2 are consistently larger than those for 9-COOH and the range of Øf values is larger. The larger Øf’s of 9,10-(COOH)2 are due to protection of the meso positions from solute-solvent interaction and the greater Øf range is due to enhanced quenching by protic solvents through strong solvent-carboxylic acid coupling. Øf measurement using trifluoroacetic acid in cyclohexane as a solvent indicate that solvent-solvent as well as solute solvent interaction may contribute to quenching.

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