10.1021/ic902166j.s002
Sarah E. Lister
Sarah E.
Lister
Anne Soleilhavoup
Anne
Soleilhavoup
Ray L. Withers
Ray L.
Withers
Paul Hodgkinson
Paul
Hodgkinson
John S. O. Evans
John
S. O. Evans
Structures and Phase Transitions in (MoO<sub>2</sub>)<sub>2</sub>P<sub>2</sub>O<sub>7</sub>
American Chemical Society
2010
MoO
cell parameters
electron diffraction data
2 D 31 P
First principles calculations
NMR parameters
space group Pnma
electron diffraction
principles quantum chemical calculations
Phase Transitions
31 P NMR
Å3
phase transitions
volume
1 D
31 P chemical shift
synchrotron data
250 K
crystal structures
J couplings
lattice parameters
423 K
room temperature
325 K
2010-03-01 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Structures_and_Phase_Transitions_in_MoO_sub_2_sub_sub_2_sub_P_sub_2_sub_O_sub_7_sub_/2788834
We report structural investigations into (MoO<sub>2</sub>)<sub>2</sub>P<sub>2</sub>O<sub>7</sub> using a combination of X-ray, neutron and electron diffraction, and solid-state NMR supported by first principles quantum chemical calculations. These reveal a series of phase transitions on cooling at temperatures of 377 and 325 K. The high temperature γ-phase has connectivity consistent with that proposed by Kierkegaard at room temperature (but with improved bond length distribution), and contains 13 unique atoms in space group <i>Pnma</i> with lattice parameters <i>a</i> = 12.6577(1) Å, <i>b</i> = 6.3095(1) Å, <i>c</i> = 10.4161(1) Å, and volume 831.87(1) Å<sup>3</sup> from synchrotron data at 423 K. The low temperature α-structure was indexed from electron diffraction data and contains 60 unique atoms in space group <i>P</i>2<sub>1</sub><i>/c</i> with cell parameters <i>a</i> = 17.8161(3) Å, <i>b</i> = 10.3672(1) Å, <i>c</i> = 17.8089(3) Å, β = 90.2009(2)°, and volume 3289.34(7) Å<sup>3</sup> at 250 K. First principles calculations of <sup>31</sup>P chemical shift and <i>J</i> couplings were used to establish correlation between local structure and observed NMR parameters, and 1D and 2D <sup>31</sup>P solid-state NMR used to validate the proposed crystal structures. The intermediate β-phase is believed to adopt an incommensurately modulated structure; <sup>31</sup>P NMR suggests a smooth structural evolution in this region.