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Three Paramagnetic Reduction Stages of Phenyl Substituted 1,2:9,10 Dibenzo[2.2]paracyclophane-1,9-dienes. Radical Anions, Triplet Dianions and Radical Trianions as studied by ESR and ENDOR Spektroscopy
Meijere, Armin de, Gerson, Fabian, König, Burkhard, Reiser, Oliver und Wellauer, Thomas (1990) Three Paramagnetic Reduction Stages of Phenyl Substituted 1,2:9,10 Dibenzo[2.2]paracyclophane-1,9-dienes. Radical Anions, Triplet Dianions and Radical Trianions as studied by ESR and ENDOR Spektroscopy. Journal of the American Chemical Society 112 (19), S. 6827-6832.Veröffentlichungsdatum dieses Volltextes: 05 Aug 2009 13:22
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DOI zum Zitieren dieses Dokuments: 10.5283/epub.255
Zusammenfassung
Reduction of di- and tetraphenyl-substituted 1,2:9,10-dibenzo[2.2]paracyclophane-1,9-dienes, 3, 3-d'₂, 4,5, and 5-tBu₄ with potassium in ethereal solvents has been monitored by ESR and ENDOR spectroscopy. In each case, the first reduction step yields a radical anion in which the unpaired electron resides in one of the two lateral biphenyl or o-terphenyl mystems orthogonal to the central phane ...
Reduction of di- and tetraphenyl-substituted 1,2:9,10-dibenzo[2.2]paracyclophane-1,9-dienes, 3, 3-d'₂, 4,5, and 5-tBu₄ with potassium in ethereal solvents has been monitored by ESR and ENDOR spectroscopy. In each case, the first reduction step yields a radical anion in which the unpaired electron resides in one of the two lateral biphenyl or o-terphenyl mystems orthogonal to the central phane unit. Except under conditions of strong association with the K⁺ counterion, electron exchange between the two π-ystems is fast on the hyperfine time scale. Upon further reduction, a second electron is taken up, as revealed by the appearance of triplet dianions bearing one unpaired electron in each of the two lateral π-ystems (separation ca. 1 nm). The singlet state of the dianion of 5 has been estimated to lie only slightly higher (ca. 2 kJ mol⁻¹) than the triplet state; the simultaneous presence of the singlet dianions of 3 and 5 in the solutions is compatible with evidence from NMR spectroscopy. An even more prolonged contact with potassium metal leads to radical trianions with the unpaired electron accommodated in the central phane unit. These radical trianions can thus be regarded as the radical anions of [2.2]paracyclophane having two negatively charged lateral π-ystems attached to it. Detection of trianions in a quartet state by ESR spectroscopy proved to be difficult under the experimental conditions used. The sequential uptake of three electrons by 3-5 is discussed in the light of the reduction potentials of the constituent π-ystems.
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| Dokumentenart | Artikel | ||||
| Titel eines Journals oder einer Zeitschrift | Journal of the American Chemical Society | ||||
| Band: | 112 | ||||
|---|---|---|---|---|---|
| Nummer des Zeitschriftenheftes oder des Kapitels: | 19 | ||||
| Seitenbereich: | S. 6827-6832 | ||||
| Datum | 1990 | ||||
| Institutionen | Chemie und Pharmazie > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Oliver Reiser Chemie und Pharmazie > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Burkhard König | ||||
| Identifikationsnummer |
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| Dewey-Dezimal-Klassifikation | 500 Naturwissenschaften und Mathematik > 540 Chemie | ||||
| Status | Veröffentlicht | ||||
| Begutachtet | Ja, diese Version wurde begutachtet | ||||
| An der Universität Regensburg entstanden | Unbekannt / Keine Angabe | ||||
| URN der UB Regensburg | urn:nbn:de:bvb:355-epub-2552 | ||||
| Dokumenten-ID | 255 |
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