Molecular Structure and Dynamics in the Low Temperature (Orthorhombic) Phase of NH3BH3
Variable temperature 2H NMR experiments on the orthorhombic phase of selectively deuterated NH3BH3 spanning the static to fast exchange limits of the borane and amine motions are reported. New values of the electric field gradient (EFG) tensor parameters have been obtained from the static 2H spectra of Vzz = 5.509(±0.275)×1014 statvolt/cm2 and ! = 0.00±0.05 for the borane hydrogens and Vzz = 9.615(±0.481)×1014 statvolt/cm2 and ! = 0.00±0.05 for the amine hydrogens. The molecular symmetry inferred from the observation of equal EFG tensors for both the boron and amine hydrogens is in sharp contrast with the Cs symmetry derived from diffraction studies. The origin of the apparent discrepancy has been investigated using molecular dynamics methods in combination with electronic structure calculations of NMR parameters, bond lengths, and bond angles. The computation of parameters from a statistical ensemble rather than from a single set of atomic Cartesian coordinates gives values that are in close quantitative agreement with the 2H NMR electric field gradient tensor measurements and are more consistent with the molecular symmetry revealed by the NMR spectra. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 985025
- Report Number(s):
- PNNL-SA-58394; ISSN 1520-5215; KC0302010; TRN: US201016%%1718
- Journal Information:
- Journal of Physical Chemistry A, 112(18):4277-4283, Vol. 112, Issue 18; ISSN 1089-5639
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMINES
BOND ANGLE
BOND LENGTHS
BORANES
BORON
CARTESIAN COORDINATES
DIFFRACTION
ELECTRIC FIELDS
ELECTRONIC STRUCTURE
MOLECULAR DYNAMICS METHOD
MOLECULAR STRUCTURE
NMR SPECTRA
ORIGIN
SPECTRA
SYMMETRY
hydrogen storage medium
intermolecular interactions
orthorhombic environment
NMR spectroscopy