Intermolecular Electron Spin Transfer between Naphthalene π-Systems Separated by a Variable Number of Spirobonded Cyclobutane Rings, An. ESR and ENDOR Study
✍ Scribed by Fabian Gerson; Walter Huber; Wiliam B. Martin Jr.; Paul Caluwe; Tim Pepper; Michael Szwarc
- Publisher
- John Wiley and Sons
- Year
- 1984
- Tongue
- German
- Weight
- 447 KB
- Volume
- 67
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
The radical anions of the compounds N1N, N3N and N5N, in which two naphthalen π‐systems are separated by 1, 3 and 5 spirobonded cyclobutane rings, respectively, and tha tof the reference compound N1, containing one naphthalene π‐system and one cyclobutane ring, have been studied by ESR and ENDOR spectroscopy under a variety of experimental conditions. The intramolecular electrons spin transfer between the two π‐moieties in N3N and N5N is slow on the hyperfine time‐scale, irrespective of the applied conditions. It is also slow in N1N, except for media of high solvating power. In such media, with a slight reduction of N1N to its radical anion, a paramagnetic species is observed, the hyperfine data for which are consistent with N1N to its radical anion, a paramagnetic species is observed, the hyperfine data of which are consistent with N1N, undergoing a fast intramolecular electron spin tansfer. The ESR and ENDOR spectra of this species are superimposed on those characteristic of a slow transfer. It is suggested that the fast and slow transfer involve the syn‐ and anti‐conformations, respectively, since the distance, r, between the two naphthalene π‐systems of N1N is considerably shorter in the former than in the latter (r = 740 vs. 880 Pm for the distance between the centres of the π‐systems). Glassy solutions of exhaustively reduced N1N display signals of the dianion triplet state, whereas no such signals are found for N3N and N5N. The zero‐field splitting parameter, D, is 4.7 mT, corresponding to r ≈ 480 pm.