Substituent-Dependent Electron Transfer in Radical Anions of 9- and 9,10-Disubstituted 2,7-Dinitro-9,10-dihydro-9,10-ethanoanthracenes

✍ Scribed by Anthony J. Manny; Robert K. Norris; Paul K. Witting

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 707 KB
• Volume: 34
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199610)34:10<761::aid-omr951>3.0.co;2-1

✦ Synopsis

Radical anions from a series of 9-substituted-and 9,1O-disubstituted-2,6-dinitro-and 2,7-dinitro-9,10-dihydro-9,10ethanoanthracenes were investigated by EPR spectroscopy at 25 "C. In the case of radical anions of compounds with nitro groups in both the 2-and &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 terf-butyl or methyl groups in the 9-positio11, 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.