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Calculation of Hyperfine Splitting Constants in Anthrasemiquinones with Electron‐Donating and ‐Withdrawing Substituents by Additivity Relations
Author(s) -
Stockfisch Dorte,
Kaaber Marianne,
Pedersen Jens A.
Publication year - 1996
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/(sici)1097-458x(199608)34:8<619::aid-omr924>3.0.co;2-a
Subject(s) - chemistry , hyperfine structure , additive function , electron paramagnetic resonance , polar effect , radical , electron , spin (aerodynamics) , resonance (particle physics) , computational chemistry , atomic physics , photochemistry , nuclear magnetic resonance , organic chemistry , quantum mechanics , thermodynamics , physics , mathematical analysis , mathematics
The hyperfine splitting constants of 11 mostly symmetric β‐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 electron‐withdrawing substituents.