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Title: Fundamental experimental and theoretical studies on the light fastness of azo dyes
Author: Guy, O. J.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2000
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Photo-degradation reactions of donor acceptor azo dyes in methanol solution have been investigated. Irradiation of the second absorption band was confirmed to be the predominant cause of permanent photo-fading under anaerobic and oxygenated conditions. Oxygen retarded the rate of photo-fading by up to 20 times. The photo-fading of dyes deposited on various substrates exhibited similar behaviour to dyes in methanol solution. The photo-products of the reaction are suggested to include amino derivatives of azo dyes containing nitro groups. Theoretical semi-empirical AMI and ab initio calculations using the 3-21G basis set, predicted reasonable structures for the ground states of dyes. Spectroscopic calculations using a version of the CNDO/S method gave good correlations between calculated transition energies and experimental data obtained in cyclohexane. The results of a multi electron configuration interaction treatment of AMI structures were in the gas phase were inconsistent with experimental spectral data obtained in cyclohexane but improved correlations were obtained between calculated transition energies and experimental data in methanol. The structures and energies of excited singlet and triplet states have also been calculated by the AMI method but there was no apparent correlation of these energies with the lightfastness of azo dyes. A tentative relationship between calculated distributions of the unpaired electrons in the second excited triplet state and the site of reactivity in the dyes was proposed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available