This thesis attempts a combined theoretical/experimental investigation of two fundamental scaling laws in charge transfer reactions: how the rate of those reactions varies as a function of distance between an electron donor and an electron acceptor and how the rate varies as a function of the number of distinct pathways between that donor and acceptor. At all points, we use photoinduced intramolecular charge transfer as a foundation on which to build our theories and as a test bed in which to evaluate them. We add to the existing body of work on the study of the distance dependence of charge transfer by advancing a new modular system, fluorene oligomers, that possesses oxidation potentials that remains relatively static as a function of length, and show very simple Arrhenius like temperature dependence, suggesting the lack of complex conformational dynamics. Both of these properties allow the weak distance dependence of charge separation to be very well described by simple kinetic analysis, while charge recombination rates still show some intriguing and (as of yet) accounted for complexity. We then describe a theoretical framework that addresses the issue of coherent summation of electronic paths over multiple distinct pathways in the presence of decoherence processes. Specific predictions are made regarding the contribution of interference phenomena and suggest that caution must be used when evaluating the contribution of interference at finite temperature. Individual Liouville space pathways are probed to get mechanistic information about which coherences survive. Constructive and destructive interference processes are discussed. Finally, we attempt to probe experimentally the marginal effect of adding additional spatial pathways. Specifically, we synthesize a novel family of benzo-annulated bicyclo[2.2.2]octane bridge groups designed to compare, in an equivalent geometry, the contribution of additional π-pathways. However, by showing charge transfer rates that are essentially independent of the number of additional fused rings, the system reveals subtle features of how orbital alignment controls the electronic coupling. Natural Bond Orbital analysis is applied and suggests strong destructive interference effects. Unexpected temperature dependences are observed but are well accounted for by molecular dynamics simulations.

Last modified

• 08/29/2018

Creator

• Randall Howard Goldsmith

DOI

• https://doi.org/10.21985/N2N72K

Subject

• Chemistry

Keyword

• molecular electronics
• donor bridge acceptor
• dephasing
• multiple pathways
• charge transfer
• bicyclooctane

Date created

• 2007-12-07

Resource type

• Dissertation

Rights statement

• In Copyright