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- Title
The Radical Anions of [2.2.2.2]Paracyclophane-1,9,17,25-tetraene and Some of its Heteroaromatic Analogues.
- Authors
Gerson, Fabian; Huber, Walter; Wennerström, Olof
- Abstract
The radical anions of [2.2.2.2]paracyclophane- 1,9,17,25-tetraene (I), [2] (2, 5)-furano [2]paracyclo [2] (2,5)furano [2]paracyclophane-1,8, 16,23-tetraene (II), [2]-(2,5)thiopheno [2]paracyclo [2] (2,5)thiopheno [2]paracyclophane-1,8,16,23-tetraene (III) and [2.2.2.2](2,5)thiophenophane-1,8,15,22-tetraene (IV) have been studied by ESR. and ENDOR. spectroscopy. The assignment of the proton coupling constants, aHμ is to a large extent based on investigations of deuteriated derivatives. These investigations impressively demonstrate the potential of ENDOR. spectroscopy as an analytical tool. The Arrhenius activation energies, Ea, for the rotation of phenylene fragments about the bonds linking them with the ethylenic parts in I⊖ and II⊖ are 36±6 and 28±4 kJ/mol, respectively. The value aHμ of the olefinic protons in I⊖ appears substantially smaller than expected for the corresponding planar radical anion. The hyperfine data for II⊖, III⊖ and IV⊖ are consistent with the conformations which should minimize the deviations of the macrocyclic π-systems from planarity. In the case of II⊖, tight ion pairs are formed by the radical anion and its counter-ion, K⊕, in DME, owing to the strong association of the alkali metal cation with one of the furan moieties. An analogous interaction of K⊕ with a thiophene moiety in III⊖ must be weaker, since no effects of ion pairing on the ESR. and ENDOR. spectra have been observed for this radical anion.
- Publication
Helvetica Chimica Acta, 1978, Vol 61, Issue 8, p2763
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.19780610803