Hybrid density functional studies of a bacteriopheophytina model and its anion radical form: Geometry, spin densities, and hyperfine couplings
✍ Scribed by O'malley, Patrick J.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 208 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
Hybrid density functional calculations are performed on models of the bacteriopheophytin a molecule, which acts as an electron acceptor in the initial electron transfer events of bacterial photosynthesis. The geometry of the neutral and one-electron reduced free radical form are calculated. Little variation in the main framework geometry is predicted to occur on one-electron reduction. The electron density of the SOMO for the anion free radical form is also investigated, and the unpaired spin density distribution is also analyzed. Anisotropic and isotropic hyperfine couplings are calculated and discussed on the basis of the unpaired spin density distributions. The electron density of the SOMO is shown to extend on to the carbonyl group attached to ring A; the extent of this delocalization being dependent on the twist angle, this group makes with the main ring plane with the magnitude of the 1 H hyperfine couplings of the 2 1 methyl group strongly dependent on the value of this twist angle. Good agreement is observed between calculated and experimentally measured isotropic hyperfine couplings.