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Energy and Electron Transfer MMP+ discussion Chapter 7 first half December 17, 2002 Zhiqiang Liu
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Transfer
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Competing Processes upon encountering
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Trivial Mechanism for energy transfer
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Spectral Overlap Integral
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Trivial Mechanism for electron transfer http://chemed.chem.purdue.edu/demos/main_pages/9.4.html
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Non-trivial energy transfer
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Forster Theory of Coulombic Energy Transfer 2 : orientation. Alignment factor J: overlap. Energy match of donor and acceptor R: distance between dipoles dipole-dipole interaction
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Energy transfer by electron exchange Dexter:
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Comparison: Forster v. Dexter Dexter: Forster: 1.Dependence on separation. Dexter much stronger than Forster. 2.Forster depends on oscillator strength. 3.Both dependent on J. 4.Dexter involves excited states
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Generating D and A*
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Triplet Triplet Annihilation. Energy transfer via electron exchange
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Electron Transfer
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Excited states: better oxidizing and reducing agents
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Free energy for gas phase electron transfer
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Free energy in solution phase GG Gas phase results + terms for solution Electrochemical potential in solution
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Coulombic term in free energy of electron transfer
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Libby vs. Marcus theory Three events: 1.Electron transfer 2.Molecular reorientation 3.Solvent reorientation Libby: Molecular and solvent after Electron. Marcus: Assumptions: 1. Loose bonding between molecules for classical phys/chem analysis 2. Geometrical and solvent reorientation to provide energy for the e jump Frank-Condon e Jump
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Libby vs. Marcus theory
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Marcus for non zero free energy difference
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Experimental evidence for Marcus Inverted Region
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