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Ashbrook SE, Dawson DM, Gan Z, Hooper JE, Hung I, Macfarlane LE, McKay D, McLeod LK, Walton RI. Application of NMR Crystallography to Highly Disordered Templated Materials: Extensive Local Structural Disorder in the Gallophosphate GaPO-34A. Inorg Chem 2020; 59:11616-11626. [PMID: 32799506 DOI: 10.1021/acs.inorgchem.0c01450] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present an NMR crystallographic investigation of two as-made forms of the recently characterized gallophosphate GaPO-34A, which has an unusual framework composition with a Ga:P ratio of 7:6 and contains both hydroxide and fluoride anions and either 1-methylimidazolium or pyridinium as the structure-directing agent. We combine previously reported X-ray crystallographic data with solid-state NMR spectroscopy and periodic density functional theory (DFT) calculations to show that the structure contains at least three distinct types of disorder (occupational, compositional, and dynamic). The occupational disorder arises from the presence of six anion sites per unit cell, but a total occupancy of five of these, leading to full occupancy of four sites and partial occupancy of the fifth and sixth (which are related by symmetry). The mixture of OH and F present leads to compositional disorder on the occupied anion sites, although the occupancy of some sites by F is calculated to be energetically unfavorable and signals relating to F on these sites are not observed by NMR spectroscopy, confirming that the compositional disorder is not random. Finally, a combination of high-field 71Ga NMR spectroscopy and variable-temperature 13C and 31P NMR experiments shows that the structure directing agents are dynamic on the microsecond time scale, which can be supported by averaging the 31P chemical shifts calculated with the SDA in different orientations. This demonstrates the value of an NMR crystallographic approach, particularly in the case of highly disordered crystalline materials, where the growth of large single crystals for conventional structure determination may not be possible owing to the extent of disorder present.
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Affiliation(s)
- Sharon E Ashbrook
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - Daniel M Dawson
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - Zhehong Gan
- Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
| | - Joseph E Hooper
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - Ivan Hung
- Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States
| | - Laurie E Macfarlane
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - David McKay
- School of Chemistry, EaStCHEM and Centre of Magnetic Resonance, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, United Kingdom
| | - Lucy K McLeod
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Richard I Walton
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom
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