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A Theoretical Model for Orientation Effects in Electron Transfer Reactions


Cave, Robert J. (1986) A Theoretical Model for Orientation Effects in Electron Transfer Reactions. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/s9zp-mj05.


In this thesis, the development and application of a model for the examination of orientation effects in electron transfer reactions are considered. The model is designed to describe broad features of the electronic interactions between large molecules, where the transferred electron is delocalized in both reactant and product.

The model employs spherical or oblate-spheroidal potentials of constant depth for the donor and acceptor sites. The Schrodinger equation is solved for the exact eigenfunctions of such a potential, and the electron transfer matrix element, TBA, is calculated us1ng these wavefunctions. TBA is the principal distance and orientation dependent quantity in current theories of nonadiabatic electron transfer. By comparison of results obtained using spherical and spheroidal wells, il was determined that both orbital shape and well shape (i.e., molecular shape) effects are important in determining the magnitude and orientation dependence of TBA.

The model was used to examine orientation dependence in electron transfer reactions between porphyrins and porphyrin derivatives. TBA was examined for a variety of mutual orientations, including: 1) face-to-face transfers, where it was found that TBA for forward transfer from photoexcited reactants was considerably larger than Lhat for back transfer to yield ground state products, 2) edge-to-edge orientations, and 3) models of possible initial donor-acceptor pairs in a bacterial photosynthetic electron transfer system (Rhodopseudomonas viridis). It was observed that TBA was a sensitive function of orbital shape and orientation.

In order to simplify the model, a semiclassical approximation was examined for the donor and acceptor wavefunctions, for both the spherical- and spheroidal-well states. The accuracy of the approximation supports the interpretations of the results obtained from the exact calculations. It also substantially reduced the calculational time involved.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Richards, John H.
Thesis Committee:
  • Richards, John H. (chair)
  • Marcus, Rudolph A.
  • Goddard, William A., III
  • Beauchamp, Jesse L.
Defense Date:29 July 1985
Record Number:CaltechTHESIS:08302019-110545286
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11777
Deposited By: Mel Ray
Deposited On:03 Sep 2019 18:03
Last Modified:16 Apr 2021 22:18

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