Photodimerization has long been of interest to researchers due to its unique mechanistic nature and broad range of potential applications. In the present study, we investigated the molecular structures and photodimerization behavior of 1,3,4,2-dioxazaboroles, a class of compounds with the capacity to undergo solid-state photodimerization. In parallel, we explored concepts of crystal engineering, with a particular focus on co-crystallization strategies. Cinnamoyl hydroxamic acid and 3-methoxy cinnamoyl hydroxamic acid were synthesized as starting materials for the preparation of 1,3,4,2-dioxazaboroles compounds. Performing a condensation reaction between 3 boronic acids and the two hydroxamic acids resulted in the synthesis of six novel dioxazaborole derivatives. The molecular structures were characterized using powder X-ray diffraction (PXRD), infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and single-crystal X-ray diffraction (SCXRD). Achieving high-purity products was essential for accurate structural elucidation, and various crystallization techniques, including sublimation, were employed to grow crystals that SCXRD could characterize. SCXRD analysis provided detailed insights into crystal packing arrangements and enabled us to analyze and make a correlation between molecular structure and photochemical reactivity. Solid-state photodimerization experiments revealed the influence of intermolecular interactions on reactivity, demonstrating how crystal engineering approaches, particularly co-crystallization, can promote favorable packing arrangements for photodimerization. Notably, 2,6-dimethyl phenyl cinnamoyl and 2,4,6-trimethyl phenyl cinnamoyl dioxazaboroles exhibited photoactivity in solution. Furthermore, co-crystallization with fumaric acid was shown to modulate their photochemical properties. Overall, this work establishes the relationship between molecular structure, crystal packing, and photochemical behavior in dioxazaboroles, highlighting the utility of crystal engineering in designing photoactive materials.
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