72901-46-3Relevant academic research and scientific papers
An E.S.R. Study of the Triborane(7) Radical Anion
Giles, Jeremy R. M.,Marti, Vernon P. J.,Roberts, Brian P.
, p. 696 - 698 (1983)
The radical anion of triborane(7), B3H7.-, has been generated in solution by abstraction of hydrogen from B3H8- and studied by e.s.r. spectroscopy; MNDO-UHF calculations suggest that B3H7.- has a cyclic C2V structure with a single bridging hydrogen.
Dynamics of ammonia borane using neutron scattering
Brown, Craig M.,Jacques, Teresa L.,Hess, Nancy J.,Daemen, Luke L.,Mamontov, Eugene,Linehan, John C.,Stowe, Ashley C.,Autrey, Tom
, p. 266 - 268 (2006)
We have used both the backscattering (HFBS) and time-of-flight (DCS) neutron spectrometers to investigate proton dynamics in ammonia borane, a compound of intense interest as a model for 'chemical hydrogen storage' materials. Results indicate that the deposition of ammonia borane on a mesoporous silicate results in longer proton residence times and lower energy barriers for proton motion compared to bulk ammonia borane. The reduced activation energy for proton motions may partly explain the improved thermolysis and lowering the activation barrier for the loss of the first equivalent of H2. In addition, the phonon density of states for neat ammonia borane compares well with other spectroscopic results, with the intense peak at 22 meV assigned to the librational NH3 and BH3 modes, whereas ammonia borane on MCM-41 displays a broad, featureless spectrum indicating a poorly crystalline material.
Quasielastic neutron scattering of -NH3 and -BH3 rotational dynamics in orthorhombic ammonia borane
Hess, Nancy J.,Hartman, Michael R.,Brown, Craig M.,Mamontov, Eugene,Karkamkar, Abhijeet,Heldebrant, David J.,Daemen, Luc L.,Autrey, Tom
, p. 85 - 88 (2009/02/01)
Energy barriers for rotation of -NH3 and -BH3 in the orthorhombic phase of ammonia borane, NH3BH3, were determined using quasielastic neutron scattering (QENS). QENS confirms the 3-site jump model of rotational
Materials for hydrogen storage: Structure and dynamics of borane ammonia complex
Parvanov, Vencislav M.,Schenter, Gregory K.,Hess, Nancy J.,Daemen, Luke L.,Hartl, Monika,Stowe, Ashley C.,Camaioni, Donald M.,Autrey, Tom
, p. 4514 - 4522 (2009/02/04)
The activation energies for rotations in low-temperature orthorhombic ammonia borane were analyzed and characterized in terms of electronic structure theory. The perdeuterated 11B-enriched ammonia borane, 11BD3ND3, sample was synthesized, and the structure was refined from neutron powder diffraction data at 175 K. This temperature has been chosen as median of the range of previously reported nuclear magnetic resonance spectroscopy measurements of these rotations. A representative molecular cluster model was assembled from the refined geometry, and the activation energies were calculated and characterized by analysis of the environmental factors that control the rotational dynamics. The barrier for independent NH3 rotation, Ea = 12.7 kJ mol-1, largely depends on the molecular conformational torsion in the solid-state geometry. The barrier for independent BH3 rotation, Ea = 38.3 kJ mol-1, results from the summation of the effect of molecular torsion and large repulsive intermolecular hydrogen-hydrogen interactions. However, a barrier of Ea = 31.1 kJ mol-1 was calculated for internally correlated rotation with preserved molecular conformation. Analysis of the barrier heights and the corresponding rotational pathways shows that rotation of the BH3 group involves strongly correlated rotation of the NH3 end of the molecule. This observation suggests that the barrier from previously reported measurement of BH3 rotation corresponds to H3B-NH3 correlated rotation.
Structure and vibrational dynamics of isotopically labeled lithium borohydride using neutron diffraction and spectroscopy
Hartman, Michael R.,Rush, John J.,Udovic, Terrence J.,Bowman Jr., Robert C.,Hwang, Son-Jong
, p. 1298 - 1305 (2008/10/09)
The crystalline structure of a 7Li and 11B labeled lithium borohydride has been investigated using neutron powder diffraction at 3.5, 360, and 400 K. The B-H bond lengths and H-B-H angles for the [BH4]- tetrahedra indicated that the tetrahedra maintained a nearly ideal configuration throughout the temperature range investigated. The atomic displacement parameters at 360 K suggest that the [BH4]- tetrahedra become increasingly disordered as a result of large amplitude librational and reorientational motions as the orthorhombic to hexagonal phase transition (T=384 K) is approached. In the high-temperature hexagonal phase, the [BH4]- tetrahedra displayed extreme disorder about the trigonal axis along which they are aligned. Neutron vibrational spectroscopy data were collected at 5 K over an energy range of 10-170 meV, and were found to be in good agreement with prior Raman and low-resolution neutron spectroscopy studies.
