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Title: Characterizing the Photochemistry and Photophysics of Benzoylbenzoate and Formylbenzoate Anions using Cryogenic Ion Spectroscopy
Summary: Marine chromophoric dissolved organic matter (mCDOM) is a large and complex class of matter predominantly found at the air-water interface in bodies of water. While it is known to generate radicals and unwanted byproducts, such as HONO· and ·OH, the mechanism of formation for these products is currently unknown. In this dissertation, a bottom-up approach is utilized to investigate possible reaction pathways by scaling down to small molecule models of mCDOM. Namely, this dissertation investigates the photochemistry and photophysics of benzoylbenzoates (BBA¯). Analysis of the UV spectrum of the deprotonated species reveal two dominant processes upon photoexcitation of 4BBA¯ yielding tag loss and decarboxylation. Analysis of the cold vibrational bands of the UV photoproducts of 2BBA¯ indicate the presence of a isomeric decarboxylate to that of 4BBA¯, as well as a radical carbanion that arises from HOCO∙ loss. This work is then extended to formylbenzoates, FBA¯, to understand isomerization following decarboxylation. FBA¯ is a structurally simpler analog to BBA¯ with similar barriers for isomerization following decarboxylation. This goal is achieved by using a H2 messenger tag as a vibrational reporter for the location of the nascent charge center in the phenide species generated by decarboxylation. Isomer-selective infrared spectra confirm facile migration of the carbanion charge center.
