Date of Award

Spring 2019

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Linda S. Shimizu

Abstract

Supramolecular assembly of benzophenone through urea hydrogen bonding interactions facilitates the formation of remarkably persistent triplet radical pairs upon UV-irradiation at room temperature, whereas no radicals are observed in solution. The generation of organic radicals is correlated to the microenvironment around the benzophenone carbonyl, the types of proximal hydrogens, and the rigid supramolecular network. High-Field EPR and variable temperature X-band EPR accompanied by simulations suggest a resonance stabilized radical pair through hydrogen abstraction. Previous work has shown that UV-irradiation of self-assembled benzophenone bis-urea host results in low quantities of radical pairs that can be used to enhance NMR signals by a factor of

4 for both the host and the encapsulated guest using a dynamic nuclear polarization (DNP) technique. This result suggests that even low levels of endogenous radicals can facilitate the study of host-guest relationships in the solid-state.2 Additionally, the photochemical formation of reactive oxygen species (ROS) by the host was examined, which was found to generate both superoxide and singlet oxygen in similar quantities. The host was then applied as a nanoreactor to mediate photooxidations of 1-methyl-1-cyclohexene while suspended in solution and as a solvent free host:guest complex.

Included in

Chemistry Commons

Share

COinS