title: Synthesis and characterization of B-heterocyclic π-radical and its reactivity as a boryl radical.
abstract: The first isolation and full characterization of the stable, persistent diazaboracyclic neutral radical 3 is reported. Reduction of base-stabilized difluororoborane 2 provided radical 3 as a neutral molecule having a planar sp(2) boron atom attached to one fluorine and two nitrogen atoms. ESR spectroscopy and DFT calculations indicated that the unpaired electron is delocalized over the six-membered ring. Because of an electronic transition related to the singly occupied molecular orbital, 3 has a characteristic red color, as UV-vis spectroscopy showed an absorption maximum at 498 nm. Although DFT calculations suggested that radical 3 has relatively low spin density on the boron atom in comparison with the nitrogen and carbon atoms in the six-membered ring, 3 reacted as a base-stabilized boryl radical when treated with benzoquinone or benzoyl peroxide.
authors.affiliation: Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Aramaki
authors.forename: Hideki
authors.initials: H
authors.lastname: Omiya
authors.forename: Makoto
authors.initials: M
authors.lastname: Yamashita
authors.forename: Koji
authors.initials: K
authors.lastname: Nakabayashi
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ohkoshi
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nozaki
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification; D008958:Models, Molecular; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D001896:Boron Compounds; D005609:Free Radicals; D006571:Heterocyclic Compounds