Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636975
Title: Fundamental studies on the solvatochromism of dyes and pigments
Author: Fitton, A. L.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2001
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Abstract:
The structure and spectroscopic properties of Phenol Blue [N-(4-dimethylaminophenyl)-1, 4-benzoquiinoneimine], which can in theory exist as either a quinoneimine or as a zwitterions have been assessed both experimentally and theoretically using molecular orbital methods. NMR evidence obtained from the more soluble dimethylamino derivative consistently demonstrates that it exists solely as the quinoneimine in all solvents. Theoretically, the solvatochromic shift of the dye in aprotic solvents, calculated using the PM3/COSMO method correlates well with the experimental data and arises because solvents with large dielectric constants are able to differentially stabilize the polar excited state. In protic solvents, the larger bathochromic shifts that occur are attributable to both a dielectric effect and a separate hydrogen bonding contribution from the solvent. In water, Phenol Blue is predicted to form a stable trihydrate that is calculated at the CNDOVS level of theory to absorb at a significantly longer wavelength than the unsolvated structure in line with the experimental data. The structure and spectroscopic properties of a second bathochromic dye (Nile Red [9-Diethylaminobenzophenoxazin-5-one]) have also been investigated by both experimental and theoretical methods and it has been found to also exist exclusively as a quinoneimine in both protic solvents and in aprotic solvents of low and high dielectric constant. The calculated results (using the PM3/COSMO method) compare favourably with the experimental data and again arise because solvents with large dielectric constants exert a much great stabilizing influence on the more polar excited state than they do on the ground state. The two contributing factors governing the size of the large positive bathochromic shift are that of a solvent dielectric effect and a separate intermolecular solute-solvent hydrogen bonding interaction. Nile Red is also predicted to form a stable trihydrate that is calculated at the CNDOVS level of theory to absorb at a significantly longer wavelength than the unsolvated structure in line with the experimental data.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.636975  DOI: Not available
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