ESR relaxation studies on orbitally degenerate free radicals.II

Das, M. R. ; Wagner, Stephen B. ; Freed, J. H. (1970) ESR relaxation studies on orbitally degenerate free radicals.II Journal of Chemical Physics, 52 (10). pp. 5404-5417. ISSN 0021-9606

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Careful linewidth and saturation studies were performed on several orbitally degenerate hydrocarbon free radicals in liquid solution as a function of temperature, solvent, and counterion, and these are compared with similar studies on nondegenerate hydrocarbon free radicals. The anomalous T1's and T2's attributed to the orbital degeneracy are found to be strikingly independent of all these variables. This is most clearly evidenced for the coronene and triphenylene anion radicals. The results for the benzene and cyclo-octatetraene anions (alkali metal prepared) are complicated by a further contribution to T2-1 which increases with temperature. This contribution is correlated with counterion and solvent dependent ion-pairing effects. The intrinsic temperature-independent T2-1's for the orbitally degenerate free radicals are surprisingly well correlated with the small but anomalous deviations of the g values for these radicals from the Segal, Kaplan, and Fraenkel experimental fit to Stone's theory of g values. This is taken as positive evidence for the role of anomalous spin-orbit interactions in the mechanism(s) yielding the anomalous relaxation times. Their independence of temperature, solvent, and counterion suggests that the relaxation mechanism(s) is largely intramolecular.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
ID Code:8525
Deposited On:27 Oct 2010 06:21
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