EPR and AM1 study of the structure of the radical anion of {beta}-ionone
- Inst. of Chemical Kinetics and Combustion, Novosibirsk (Russian Federation)
- Univ. of Alabama, Tuscaloosa, AL (United States). Chemistry Dept.
The structure of the radical anion of {beta}-ionone has been investigated by EPR and AM1 molecular modeling methods as a part of a study to determine the structure and magnetic properties of intermediates of one-electron transfer reactions of carotenoids. Analysis of the temperature dependence of the EPR spectrum of the radical anion shows that the largest hyperfine coupling of 16 G previously assigned to the 7-H proton should be assigned to the 4-H proton in the axial orientation. The previous assignment failed to account for rate of the cyclohexene ring inversion. Comparing the resolved EPR spectra at various temperatures indicates that the coupling of 7-H proton equals {approx}9.5 G. The structure of the radical anion predicted by AM1 molecular modeling is in agreement with this analysis. From the temperature dependence the rate of the cyclohexene ring inversion in the radical anion at room temperatures is approximately 6 {times} 10{sup 7} s{sup {minus}1} with an activation energy of about 7 kcal/mol.
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Russian Foundation for Basic Research (Russian Federation)
- OSTI ID:
- 332705
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Journal Name: Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory Journal Issue: 10 Vol. 103; ISSN 1089-5639; ISSN JPCAFH
- Country of Publication:
- United States
- Language:
- English
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