ENDOR studies of semiquinone radical ions in liquid crystalline solutions
β Scribed by Burkhard Kirste
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- English
- Weight
- 891 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0749-1581
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β¦ Synopsis
Studies of a series of substituted benzo-, naphtho-, anthra-and phenanthrene-semiquinones, benzil semidione and Wurster's blue perchlorate by ENDOR spectroscopy in liquid crystalline solutions are reported. Sufficient solubility of the radical anions is achieved by using lipophilic counter ions such as benzyltrimethylammonium. The effects of ion pairing were investigated, particularly in the case of benzil semidione, which can adopt cis or trans configurations. The anisotropic hyperfine shifts observed in nematic or smectic phases are interpreted by means of calculated dipolar hyperfine tensors. A detailed picture of the alignment of the radical ions in liquid crystalline solvents is obtained. The calculated hyperfine tensors are checked for consistency with experiment, and in some cases compared with measurements in solid solution.
π SIMILAR VOLUMES
In the liquid crystal "Phase IV" which exhibits its nematic range between 16 and 76 "C ENDOR spectra of perinaphthenyi and tri-t-butylphencxyl radicals collld be recorded. it is demonstrated that the combined use of the ENDOR and liquid crystal methods yieIds valuabIe structural information.
The cation radical of canthaxanthin was generated electrochemically in dichloromethane and its solution ENDOR spectrum is reported for the first time. The isotropic proton hypertine coupling constants are in reasonable agreement with those calculated by RHF-INDO/SP molecular orbital methods for a pl
The analysis of the Iine'shifts yields ezq;3 Q//I = -2.5 MHz. This result could be rationalized by a population analysis of the nitrogen bonds, The theory predicts that the main contribution to the observed splitting comes from ihc unpzked n-electron.