Calculation of Hyperfine Splitting Constants in Anthrasemiquinones with Electron-Donating and -Withdrawing Substituents by Additivity Relations
✍ Scribed by Dorte Stockfisch; Marianne Kaaber; Jens A. Pedersen
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 489 KB
- Volume
- 34
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
The hyperfine splitting constants of 11 mostly symmetric fi-substituted anthraquinones, with electron-donating (methyl) and electron-withdrawing (carboxyl) substituents, were calculated by means of additivity principles. The calculated hyperfine constants are compared with experimental values obtained from electron spin resonance spectra of the corresponding anthrasemiquinone radicals. A close match is observed for all constants studied, and the consistent assignment found agrees completely with one previously put forward for 31 asymmetric substituted anthraquinones. It is shown experimentally that electron-donating substituents at C-2 increase the spin densities at C-1, C-6 and C-8 and decrease them at C-3, C-4, C-5 and C-7. The opposite effect is observed for electronwithdrawing substituents.