Energy and Electron Transfer MMP+ discussion Chapter 7 first half December 17, 2002 Zhiqiang Liu
Transfer
Competing Processes upon encountering
Trivial Mechanism for energy transfer
Spectral Overlap Integral
Trivial Mechanism for electron transfer
Non-trivial energy transfer
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
Energy transfer by electron exchange Dexter:
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
Generating D and A*
Triplet Triplet Annihilation. Energy transfer via electron exchange
Electron Transfer
Excited states: better oxidizing and reducing agents
Free energy for gas phase electron transfer
Free energy in solution phase GG Gas phase results + terms for solution Electrochemical potential in solution
Coulombic term in free energy of electron transfer
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
Libby vs. Marcus theory
Marcus for non zero free energy difference
Experimental evidence for Marcus Inverted Region