Diazaboroles: Experimental Investigations of their Dynamic Covalent Nature and Computational Chemistry
Abeysinghe, Janaka Prasad
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Diazaboroles have interesting optical and electronic properties. They are soluble in many organic solvents, electrochemically active, and thermally stable. The understanding of diazaboroles’ dynamic covalent behavior is important for the synthesis and incorporation in complex molecular architectures like fully p-conjugated, non-collapsible, and shape-persistent macromolecules. The present study involves the influence of solvent on diazaborole formation and its dynamic covalent behavior under various conditions. XRD structural determination was carried out for structural identification of diazaborole; moreover, computational calculations were used to compare experimental and theoretical results. The investigation of the solvent effect on diazaborole formation is important when synthesizing more complex diazaborole based molecular architectures. Therefore, the effect of the solvent on diazaborole formation was investigated and identified that only solvent evaporation time was sufficient to obtain greater diazaborole formation in high boiling solvents. Even though high reaction temperature leads to high diazaborole production, the functional groups of the solvents show less impact on the reaction. The reversibility of diazaborole formation was examined by considering diazaborole transamidation and exchange reactions with different diazaborole substituents. The results illustrate that transamidation reactions of diazaboroles are reversible. Computational calculations reveal the bond angle and bond length deviation of diazaborole isostructures (analogues). Further, electrostatic potential maps disclose the existence of an electron rich phenyl ring in diazaborole. The Gibbs free energy values of diazaborole formation in the solvent phase reveal the reaction favorability of diazaborole formation in some solvents under appropriate conditions.