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Substituent‐Dependent Electron Transfer in Radical Anions of 9‐ and 9,10‐Disubstituted 2,7‐Dinitro‐9,10‐dihydro‐9,10‐ethanoanthracenes
Author(s) -
Manny Anthony J.,
Norris Robert K.,
Witting Paul K.
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(199610)34:10<761::aid-omr951>3.0.co;2-1
Subject(s) - chemistry , substituent , methylene , nitro , electron paramagnetic resonance , intramolecular force , ring (chemistry) , photochemistry , electron transfer , hyperfine structure , medicinal chemistry , crystallography , stereochemistry , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics , alkyl
Radical anions from a series of 9‐substituted‐ and 9,10‐disubstituted‐2,6‐dinitro‐ and 2,7‐dinitro‐9,10‐dihydro‐9,10‐ethanoanthracenes were investigated by EPR spectroscopy at 25°C. In the case of radical anions of compounds with nitro groups in both the 2‐ and 6‐positions, hyperfine coupling constants (HFCs) arose from hydrogen and nitrogen atoms on the aromatic ring bearing the nitro group together with a further coupling to one methylene proton of the bridging group anti to the nitro substituent. By contrast, radical anions derived from compounds bearing nitro groups in both the 2‐ and 7‐positions in a number of instances exhibited intramolecular electron transfer which was fast on the EPR time‐scale with respect to both nitrogen and hydrogen, with HFCs arising from magnetic nuclei on both nitrophenyl rings, with further coupling from two methylene protons of the bridging group. The relative rate on the EPR time‐scale of electron transfer for the latter group of compounds showed a subtle substituent dependence. With tert ‐butyl or methyl groups in the 9‐position, or nitro groups in both the 9‐ and 10‐positions, localization of spin density to one nitrophenyl ring resulted and HFCs were similar to those for the slow exchange systems.