Aaron Michael Day



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Molecular photo-switches find use in many different applications including the design of molecular machines, controlling liquid crystal orientation and photo-pharmacology to control the activity of drugs. Azobenzene is a well-known molecular photo-switch and its derivatives have been shown to aggregate into structures that are able to maintain their dynamic photoswitching capabilities. The capability of forming dynamic aggregates can be applied to many derivatives of azobenzene, however, few have been investigated. In this work, spectroscopic methods have been implemented to categorize, analyze and describe the behavior of the many aggregates that these derivatives can form alone or with each other. Through the application of these methods, Azobenzene-4,4’-dicarboxylic acid (ADA) and 4-dimethylaminoazobenzene-4’-carboxylic acid (M0423) were examined spectroscopically and found to undergo the onset of both homo- and hetero-aggregation at a pH of 5. UV-Vis spectroscopy confirmed that these molecular photo-switches formed H-aggregates with the highest order at a ratio of 2:1 M0423 to ADA. An additional photo-switch, Azobenzene-3,3’-dicarboxylic acid (A1598), was evaluated similarly and, when paired with M0423, also showed the formation of aggregates at a pH of 5 at a ratio of 2:1 M0423 to A1598. Aggregation was analyzed with CD spectroscopy, which showed high signals indicating a higher level of chirality and thus ordered aggregation. A blue shift was observed for this pairing, showing a tendency for H-aggregate geometry.

Publication Date


Project Designation

Graduate Research

Primary Advisor

Angela Mammana

Primary Advisor's Department



Stander Symposium project, College of Arts and Sciences

A Spectroscopic Study of Photoswitching and Non-Photoswitching Azobenzene Derivatives in the Formation of Dynamic Aggregates