Date of Award

Fall 2019

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Linda S. Shimizu

Second Advisor

Aaron K. Vannucci

Abstract

Self-assembly of photoactive compounds in the solid-state can give rise to new photophysical properties. Key to these properties, is how these compounds can be organized in a uniform way. For this, hydrogen bonding building blocks can be used to guide the assembly of these compounds into organized structures. For instance, ureas, thioureas, and squaramides which contain both hydrogen bond donors and acceptors can guide the assembly of small m-xylene macrocycles in three distinct manners: 1-D columns, edge-to-face Herringbone patterns, and interdigitated networks. The former of these is commonly employed in our group to make either linear or macrocyclic dimers to study the effects self-assembly has on the stability of photogenerated radicals. For example, UV- irradiation of urea assembled triphenylamine linear dimers results in the formation of persistent radicals, whereas in solution any generated radicals are unstable and quickly terminate. In this case, approximately 1 in 150 molecules generate a radical upon UV- irradiation with a half-life of one week. Most intriguingly, re-exposure to UV-irradiation can restore the radical concentration to its original amount without damaging the bulk material. For the macrocyclic case, the 1-D columns that are formed from self-assembly are permeable to small guests which can be loaded into the framework in a single-crystal- to-single-crystal fashion. When loaded, the guest molecules play a major role in how much radical is formed upon UV-irradiation, and still display radical regenerative properties similar to the linear dimer case. Overall, this work will highlight how supramolecular assembly controls the resulting photophysical properties of a material.

Available for download on Thursday, December 16, 2021

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