87826-13-9Relevant academic research and scientific papers
Ring strain in boroxine rings: Computational and experimental considerations
Beckmann, Jens,Dakternieks, Dainis,Duthie, Andrew,Lim, Allan E.K.,Tiekink, Edward R.T.
, p. 149 - 156 (2001)
B3LYP/6-311+G(d) calculations indicate that (HBO)3 (4) and (HBO)4 (5) possess (zero-point energy corrected) strain enthalpies of 11.4 and 31.6 kJmol-1, respectively. The absence of eight-membered (RBO)4 rings is attributed to a combination of ring strain and the lability of the B-O bond. The synthesis, characterization and molecular structure of (PhBO)3·pyridine (1) are described and chemical phenomena related to the addition of amines to triorganoboroxine rings are rationalized in terms of relief of ring strain in 4.
B3O3Ph3(7-azaindole): Structure, luminescence, and fluxionality
Wu,Wu, Gang,Brancaleon, Lorenzo,Wang, Suning
, p. 2553 - 2556 (1999)
A 7-azaindole adduct of boroxine, B3O3Ph3-(7-azaindole), 1, was obtained from the reaction of PhB-(OH)2 with 7-azaindole. The crystal structure of 1 shows that the 7-azaindole ligand is bonded to the boroxine molecule through a B-N bond and an H?O hydrogen bond. Compound 1 is fluorescent in solution and the solid state. There is, however, a dramatic difference in the emission maximum of the solution (λmax = 368 nm) and solid (λmax = 400 nm) spectra. The solution behavior of 1 was examined by 1H NMR spectroscopic methods, which established that compound 1 is highly fluxional in solution, attributable to an intermodular 7-azaindole ligand dissociation/association process with an activation energy of 34 ± 1.5 kJ mol-1. To determine the role of the hydrogen bond in the dynamic process of 1, the structure and solution behavior of B3O3Ph3(Py), 2, was also examined. In solution compound 2 undergoes an intermodular exchange process similar to that of compound 1, with an activation energy of 39 ± 1.5 kJ mol-1. The relatively small activation energy in 1 could be attributed to the hydrogen bond and the reduced base strength of 7-azaindole, relative to that of pyridine.
Effect of para-substituents and solvent polarity on the formation of triphenylboroxine·amine adducts
Kua, Jeremy,Fletcher, Matthew N.,Iovine, Peter M.
, p. 8158 - 8166 (2008/10/09)
Density functional theory (B3LYP//6-311+G*) calculations including Poisson-Boltzmann implicit solvent and NMR were used to study the formation of a series of para-substituted triphenylboroxine·amine adducts with respect to their phenylboronic acid monomers and free amine in solution. Our calculations suggest that the intermediate prior to forming trimer·amine is a dimeramine adduct. Formation of dimeramine can proceed via two pathways. Electron-donating substituents favor dimerization of two monomers before addition of the amine, and electron-withdrawing substituents favor formation of a monomer·amine adduct before addition of the second monomer. We also find that π-electron acceptors destabilize formation of the dimer and trimer with respect to its monomers. Electron-withdrawing substituents favor adduct formation. Adduct formation is enthalpically stabilized by increasing the polarity of the solvent but differential solubility of the monomer compared to trimer·amine also has an effect on the equilibrium constant.
