Segregation of Charge in Ions of Dibenzo[a,c]naphthacene: Relation of Topology and Electronic Structure. An NMR, ESR, and ENDOR Study
✍ Scribed by Yoram Cohen; Yigal Fraenkel; Mordecai Rabinovitz; Patrick Felder; Fabian Gerson
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- German
- Weight
- 510 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
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'Hand '3C-chemical shifts of the dianion of dibenzo [a,c]naphthacene (1) have unambiguously been assigned by 2D-NMR spectroscopy. They indicate a remarkable charge distribution, as most of the negative charge is localized on the 'anthracenic' moiety, while the 'phenanthrenic' moiety is almost neutral. Association of I*with alkali-metal counterions has only a minor effect on the chemical shifts. The charge partitioning in 1*-, which is reproduced by wp calculations in the frame of the Huckel model, must, thus, be considered as an intrinsic property of the 4nn-electron system of 1*-. It is rationalized in terms of differing energy contents of the constituent anthracenic and phenanthrenic moieties. ESR and ENDOR studies of the radical anion 1' and the radical cation 1' show that the n-charge distribution in 1*is reflected by the n-spin distributions in the two radical ions of the alternant hydrocarbon 1.