title: Photo- and thermal-induced multistructural transformation of 2-phenylazolyl chelate boron compounds.
abstract: The new N,C-chelate boron compounds B(2-phenylazolyl)Mes2 [Mes = mesityl; azolyl = benzothiazolyl (1a), 4-methylthiazolyl (2a), benzoxazolyl (3a), benzimidazolyl (4a)] undergo an unprecedented multistructural transformation upon light irradiation or heating, sequentially producing isomers b, c, d, and e. The dark isomers b generated by photoisomerization of a undergo a rare thermal intramolecular H-atom transfer (HAT), reducing the azole ring and generating new isomers c, which are further transformed into isomers d. Remarkably, isomers d can be converted to their diastereomers e quantitatively by heating, and e can be converted back to d by irradiation at 300 nm. The structures of isomers 1d and 1e were established by X-ray diffraction. The unusual HAT reactivity can be attributed to the geometry of the highly energetic isomers b and the relatively low aromaticity of the azole rings. The boryl unit plays a key role in the reversible interconversion of d and e, as shown by mechanistic pathways established through DFT and TD-DFT calculations.
authors: Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6.
authors: Ying-Li
authors: YL
authors: Rao
authors: Hazem
authors: H
authors: Amarne
authors: Leanne D
authors: LD
authors: Chen
authors: Matthew L
authors: ML
authors: Brown
authors: Nicholas J
authors: NJ
authors: Mosey
authors: Suning
authors: S
authors: Wang
mesh_terms: D001393:Azoles / Q000138:chemical synthesis* / Q000737:chemistry; D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D055668:Photochemical Processes; D011789:Quantum Theory; D013696:Temperature
chemical_list: D001393:Azoles; D001896:Boron Compounds; D002614:Chelating Agents