Cargando…

An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites

[Image: see text] NMR crystallography has recently been applied to great effect for silica zeolites. Here we investigate whether it is possible to extend the structural information available from routine NMR spectra via a simple structure–spectrum relationship. Unlike previous empirically derived re...

Descripción completa

Detalles Bibliográficos
Autores principales: Dawson, Daniel M., Moran, Robert F., Ashbrook, Sharon E.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2017
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523116/
https://www.ncbi.nlm.nih.gov/pubmed/28751927
http://dx.doi.org/10.1021/acs.jpcc.7b03730
_version_ 1783252272251142144
author Dawson, Daniel M.
Moran, Robert F.
Ashbrook, Sharon E.
author_facet Dawson, Daniel M.
Moran, Robert F.
Ashbrook, Sharon E.
author_sort Dawson, Daniel M.
collection PubMed
description [Image: see text] NMR crystallography has recently been applied to great effect for silica zeolites. Here we investigate whether it is possible to extend the structural information available from routine NMR spectra via a simple structure–spectrum relationship. Unlike previous empirically derived relationships that have compared experimental crystal structures for (often disordered) silicates with experimental NMR spectra, where the structure may not be an accurate representation of the material studied experimentally, we use NMR parameters calculated by density functional theory (DFT) for both model Si(OSi(OH)(3))(4) clusters and also extended zeolitic SiO(2) frameworks, for which the input structure corresponding to the NMR parameters is known exactly. We arrive at a structure–spectrum relationship dependent on the mean Si–O bond length, mean Si–O–Si bond angle, and the standard deviations of both parameters, which can predict to within 1.3 ppm the (29)Si isotropic magnetic shielding that should be obtained from a DFT calculation. While this semiempirical relationship will never supersede DFT where this is possible, it does open up the possibility of a rapid estimation of the outcome of a DFT calculation where the actual calculation would be prohibitively costly or otherwise challenging. We also investigate the structural optimization of SiO(2) zeolites using DFT, demonstrating that the mean Si–O bond lengths all tend to 1.62 Å and the distortion index tends to <2.0°, suggesting that these metrics may be suitable for rapid validation of whether a given crystal structure represents a realistic local geometry around Si, or merely a bulk average with contributions from several different local geometries.
format Online
Article
Text
id pubmed-5523116
institution National Center for Biotechnology Information
language English
publishDate 2017
publisher American Chemical Society
record_format MEDLINE/PubMed
spelling pubmed-55231162017-07-25 An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites Dawson, Daniel M. Moran, Robert F. Ashbrook, Sharon E. J Phys Chem C Nanomater Interfaces [Image: see text] NMR crystallography has recently been applied to great effect for silica zeolites. Here we investigate whether it is possible to extend the structural information available from routine NMR spectra via a simple structure–spectrum relationship. Unlike previous empirically derived relationships that have compared experimental crystal structures for (often disordered) silicates with experimental NMR spectra, where the structure may not be an accurate representation of the material studied experimentally, we use NMR parameters calculated by density functional theory (DFT) for both model Si(OSi(OH)(3))(4) clusters and also extended zeolitic SiO(2) frameworks, for which the input structure corresponding to the NMR parameters is known exactly. We arrive at a structure–spectrum relationship dependent on the mean Si–O bond length, mean Si–O–Si bond angle, and the standard deviations of both parameters, which can predict to within 1.3 ppm the (29)Si isotropic magnetic shielding that should be obtained from a DFT calculation. While this semiempirical relationship will never supersede DFT where this is possible, it does open up the possibility of a rapid estimation of the outcome of a DFT calculation where the actual calculation would be prohibitively costly or otherwise challenging. We also investigate the structural optimization of SiO(2) zeolites using DFT, demonstrating that the mean Si–O bond lengths all tend to 1.62 Å and the distortion index tends to <2.0°, suggesting that these metrics may be suitable for rapid validation of whether a given crystal structure represents a realistic local geometry around Si, or merely a bulk average with contributions from several different local geometries. American Chemical Society 2017-06-16 2017-07-20 /pmc/articles/PMC5523116/ /pubmed/28751927 http://dx.doi.org/10.1021/acs.jpcc.7b03730 Text en Copyright © 2017 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
spellingShingle Dawson, Daniel M.
Moran, Robert F.
Ashbrook, Sharon E.
An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title_full An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title_fullStr An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title_full_unstemmed An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title_short An NMR Crystallographic Investigation of the Relationships between the Crystal Structure and (29)Si Isotropic Chemical Shift in Silica Zeolites
title_sort nmr crystallographic investigation of the relationships between the crystal structure and (29)si isotropic chemical shift in silica zeolites
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523116/
https://www.ncbi.nlm.nih.gov/pubmed/28751927
http://dx.doi.org/10.1021/acs.jpcc.7b03730
work_keys_str_mv AT dawsondanielm annmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites
AT moranrobertf annmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites
AT ashbrooksharone annmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites
AT dawsondanielm nmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites
AT moranrobertf nmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites
AT ashbrooksharone nmrcrystallographicinvestigationoftherelationshipsbetweenthecrystalstructureand29siisotropicchemicalshiftinsilicazeolites