<i>Cis-trans </i>photoisomerisation of 4 simple disperse azo dyes and a series of reactive azo dyes has been studied by <sup>1</sup>H nuclear magnetic resonance (NMR) spectroscopy, with an <i>in situ</i> laser irradiation of the sample. The laser irradiation was coupled into the sample within the NMR magnet <i>via</i> an optical fibre. This enabled the first <sup>1</sup>H NMR measurements to be made of the transient <i>cis</i> isomers of 4-(4-nitrophenylazo)aniline, (Disperse Orange 3), and 4-[N-ethyl-N-(2-hydroxyethyl)amino]-4’-nitroazobenzene, (Disperse Red 1). Typical NMR methods including <sup>1</sup>H 1D, <sup>1</sup>H-<sup>1</sup>H 2D COSY and <sup>1</sup>H-<sup>1</sup>H 2D EXSY/NOESY, were used to assign <sup>1</sup>H resonances of the <i>trans </i>and <i>cis</i> isomers. <i>Ab initio</i> calculations were used to predict the chemical shifts of <i>cis</i> and <i>trans</i> isomers of the disperse dyes, in good agreement, with the experimental results, and to rationalise the chemical shift changes observed on isomerisation. The technique of NMR with <i>in situ</i> laser irradiation has enabled the examination of the kinetics of <i>cis</i>-<i>trans</i> isomerisation of the series of reactive dyes, showing that the technique has great potential for correlating structure with light fastness properties of dyes. The high resolution of NMR yields unambiguous kinetic information that is currently unobtainable due to the limitations of traditional methods. Calculated minimum energy structures of both <i>cis</i> and <i>trans </i>isomers of a selection of the reactive dyes serve to rationalise experimentally determined kinetics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:662697 |
| Date | January 2005 |
| Creators | Tait, Katrina Marion |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13070 |
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