Theoretical studies of borazynes and azaborines

Inorganic Chemistry
Paul J Fazen, Luke A Burke

Abstract

Four isomers of didehydroborazine, B3N3H4, borazyne, and three isomers of azaborine, C4H4BN, are studied by DFT, CCSD, and CCSD(T) computational methods. The singlets of 1,2-borazyne (I) and 1,4-borazyne (IV) have angles about the boron of ca. 150 degrees . In 1,2-azaborine (V), the angles are ca. 140 degrees , while the N angles are ca. 112 degrees except in IV (127 degrees ) and 1,4- azaborine (VII, 120 degrees ). These geometries are almost reversed in the triplets. The 1,3-borazyne (III) shows more bicyclic character than the corresponding m-benzyne, with an N-N distance of 1.7 A. In all cases I was found to be lower in energy than the 2,4-borazyne (II), III, and IV. The order of stability of the azaborines is V > VII > 1,3- azaborine (VI). The nucleus-independent chemical shift (NICS) indicates that all isomers of borazyne are less aromatic than benzene and all isomers of azaborine are about as aromatic as benzene. Time-dependent DFT (TD-DFT) is used to study the excited states of the singlets. The significant structural differences between the singlet and triplet states suggest long phosphoresence lifetimes.

References

Feb 16, 2002·The Journal of Organic Chemistry·Michal K CyrañskiPaul von Ragué Schleyer
Jul 3, 1996·Journal of the American Chemical Society·Paul von Ragué SchleyerNicolaas J R van Eikema Hommes

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Citations

Aug 7, 2013·Journal of the American Chemical Society·Eric R AbbeyShih-Yuan Liu
Oct 12, 2010·Organic & Biomolecular Chemistry·Holger F Bettinger, Matthias Filthaus
Feb 21, 2019·Angewandte Chemie·Klara EdelHolger F Bettinger
Jul 22, 2014·Angewandte Chemie·Matthias MüllerHolger F Bettinger
Jul 14, 2011·Angewandte Chemie·Ashley N LammShih-Yuan Liu
Jun 23, 2015·Angewandte Chemie·Klara EdelHolger F Bettinger
Sep 8, 2009·Journal of Chemical Theory and Computation·Janet E Del BeneJosé Elguero
May 16, 2008·Journal of the American Chemical Society·Eric R AbbeyShih-Yuan Liu
Jan 5, 2021·The Journal of Physical Chemistry. a·Robert W LambCharles Edwin Webster

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