SYNTHESIS, CHARACTERIZATION AND COMPUTATIONAL STUDIES OF 3-ALKYLBENZOXAZABOROLES
Rathnayaka Mudiyansel, Chathurika Rathnayaka
MetadataShow full item record
Dioxaboroles, or boronate esters, are widely used to construct organic molecular architectures, such as covalent organic frameworks, due to their dynamic covalent nature. Oxazaboroles are structurally similar to dioxaboroles in which one oxygen atom is replaced by a nitrogen atom. This motif is expected to have overlapping properties of dioxaboroles, but they have yet to be incorporated into molecular architectures. Therefore, there may exist the potential for benzoxazaboroles to be used in the construction of covalent organic frameworks. With the additional valence of the nitrogen atom there is also the possibility of further functionalization and tuning of electronic properties. Previously, our research group has explored the preliminary synthesis and characterization of several benzoxazaboroles. In the current work we have synthesized several new benzoxazaboroles using 2-(alkylamino)phenols and phenylboronic acid derivatives. bis(Benzoxazaborole)s were synthesized using 2-aminophenol or 2-(alkylamino)phenols and diboronic acids. Characterization of benzoxazaboroles and bis(benzoxazaborole)s was carried out using 1H NMR, 13C NMR, UV-visible, and fluorescence spectroscopic methods. X-ray crystallographic analysis was also used for structural identification. Furthermore, dynamic covalent exchange reactions were conducted with 3-(alkyl)benzoxazaboroles and benzodioxaboroles to determine equilibrium constants and Gibbs free energy values for the benzoxazaborole exchange reactions. Finally, computational calculations of benzoxazaboroles and bis(benzoxazaborole)s were utilized to support and add to the experimental results. This includes calculations of bond lengths, HOMO-LUMO energies, and Gibbs free energy values for benzoxazaborole exchange reactions.