@article {1115,
	title = {Solid state NMR method for the determination of 3D zeolite framework/sorbate structures: H-1/Si-29 CP MAS NMR study of the high-loaded form of p-xylene in ZSM-5 and determination of the unknown structure of the low-loaded form},
	journal = {Journal of the American Chemical Society},
	volume = {127},
	number = {20},
	year = {2005},
	note = {ISI Document Delivery No.: 928AXTimes Cited: 22Cited Reference Count: 57},
	month = {May},
	pages = {7543-7558},
	type = {Article},
	abstract = {A general protocol is described for structure determinations of organic sorbate-zeolite complexes based on the selective, through-space, distance-dependent transfer of magnetization from protons in selectively deuterated organics to framework silicon nuclei. The method was developed using the known structure of the high-loaded ZSM-5/p-xylene complex containing p-xylene-d(6) or p-xylene-d(4). It was then applied to determine the unknown structure of the low-loaded ZSM-5/p-xylene complex using NMR alone. For the high-loaded complex improved data were obtained below 273 K, where slow motions and exchange processes of the p-xylene are eliminated. The general approach was validated by. the exact agreement of the experimental H-1-Si-29 CPMAS spectra obtained at a specific contact time and the complete 24-line spectra simulated using 1/T-CP vs M-2 correlations from only the six clearly resolved resonances. For the low-loaded complex the Si-29 resonances were assigned at 267 K, and variable contact time CP experiments were carried out between 243 and 173 K using the same specifically deuterated p-xylenes. All possible locations and orientations of the p-xylene guests were sampled, and those solutions that gave acceptable linear 1/T-CP vs M-2 correlations were selected. The optimum p-xylene location in this temperature range was determined to be in the channel intersection with the long molecular axis parallel to [0,1,0] (ring center fractional coordinates {-0.009, 0.250, 0.541}) with the ring plane oriented at an angle of 30 +/- 3 degrees about the crystallographic b axis. A subsequent single-crystal X-ray study confirmed this predicted structure.},
	keywords = {3-DIMENSIONAL BONDING CONNECTIVITIES, CROSS-POLARIZATION, CRYSTAL STRUCTURE-ANALYSIS, LATTICE, MAGIC-ANGLE, NATURAL-ABUNDANCE, NUCLEAR-MAGNETIC-RESONANCE, PROTON-ENHANCED NMR, SINGLE-CRYSTAL, SPINNING NMR, structures},
	isbn = {0002-7863},
	url = {<Go to ISI>://000229244600061},
	author = {Fyfe, C. A. and Diaz, A. C. and Grondey, H. and Lewis, A. R. and Forster, H.}
}
@article {382,
	title = {Combined solid state NMR and X-ray diffraction investigation of the local structure of the five-coordinate silicon in fluoride-containing as-synthesized STF zeolite},
	journal = {Journal of the American Chemical Society},
	volume = {124},
	number = {26},
	year = {2002},
	note = {ISI Document Delivery No.: 567YYTimes Cited: 41Cited Reference Count: 48},
	month = {Jul},
	pages = {7770-7778},
	type = {Article},
	abstract = {The local structure of the [SiO4/2F](-) unit in fluoride-containing as-synthesized STF zeolite has been experimentally determined by a combination of solid-state NMR and microcrystal X-ray diffraction to be very close to trigonal bipyramidal. Because the fluoride ions are disordered over two sites, the resulting local structure of the [SiO4/2F](-) unit from a conventional XRD refinement is an average between tetrahedral SiO4/2 and five-coordinate [SiO4/2F](-), giving an apparent F-Si distance longer than expected. The correct F-Si distance was determined by slow spinning MAS and fast spinning F-19/Si-29 CP and REDOR solid-state NMR experiments and found to be between 1.72 and 1.79 Angstrom. In light of this, the X-ray structure was re-refined, including the disorder at Si3. The resulting local structure of the [SiO4/2F]- unit was very close to trigonal bipyramidal with a F-Si distance of 1.744 (6) Angstrom, in agreement with the NMR results and the prediction of Density Functional Theory calculations. In addition, further evidence for the existence of a covalent F-Si bond is provided by a F-19{\textendash}>Si-29 refocused INEPT experiment. The resonance for the five-coordinate species at -147.5 ppm in the Si-29 Spectrum is a doublet due to the F-19/Si-29 J-coupling of 165 Hz. The peaks in this doublet have remarkably different effective chemical shift anisotropies due to the interplay of the CSA, dipolar coupling, and J-coupling tensors. The distortions from tetrahedral geometry of the neighboring silicon atoms to the five-coordinate Si3 atom are manifested in increased delta(aniso) values. This information, along with F-Si distances measured by F-19{\textendash}>Si-29 CP experiments, makes it possible to assign half of the Si-29 resonances to unique tetrahedral sites. As well as determining the local geometry of the [SiO4/2F](-) unit, the work presented here demonstrates the complementarity of the solid-state NMR and X-ray diffraction techniques and the advantages of using them together.},
	keywords = {5-COORDINATE SILICON, C-13 NMR, CONTAINING OCTADECASIL, CROSS-POLARIZATION, DISTANCE DETERMINATIONS, LOCATION, MOLECULAR-SIEVES, P-31 NMR, POLARIZATION TRANSFER, PROTON-ENHANCED NMR},
	isbn = {0002-7863},
	url = {<Go to ISI>://000176516400032},
	author = {Fyfe, C. A. and Brouwer, D. H. and Lewis, A. R. and Villaescusa, L. A. and Morris, R. E.}
}
@article {5080,
	title = {Location of the fluoride ion in tetrapropylammonium fluoride silicalite-1 determined by H-1/F-19/Si-29 triple resonance CP, REDOR, and TEDOR NMR experiments},
	journal = {Journal of the American Chemical Society},
	volume = {123},
	number = {28},
	year = {2001},
	note = {ISI Document Delivery No.: 451LFTimes Cited: 48Cited Reference Count: 50},
	month = {Jul},
	pages = {6882-6891},
	type = {Article},
	abstract = {The location of the fluoride ion in tetrapropylammonium fluoride silicalite-1 ([TPA]-F-[Si-MFI]), an as-synthesized siliceous zeolite with the MEI topology, has been unambiguously determined using solid-state NMR experiments alone. With the H-1 {\textendash}> Si-29 CP-INADEQUATE experiment, the 12 peaks in the highly resolved Si-29 MAS NMR spectrum of [TPA]-F-[Si-MFI] were assigned. Using these peak assignments it was possible to perform H-1/F-19/Si-29 triple resonance CP, REDOR, and TEDOR experiments to measure F-Si distances and thus locate the fluoride ion. It is covalently bonded to Si-9 in the [4(1)5(2)6(2)] cage of the zeolite framework and exchanges between two "mirror-related" Si-9 sites, making them equivalent on the NMR time scale. The importance of this result and the general applicability of the approach are discussed.},
	keywords = {3-DIMENSIONAL BONDING CONNECTIVITIES, 5-COORDINATE, CONTAINING OCTADECASIL, CROSS-POLARIZATION NMR, CRYSTAL-STRUCTURE, DETERMINATIONS, DISTANCE, MAS-NMR, NATURAL-ABUNDANCE, PROTON-ENHANCED NMR, SILICON, SOLID-STATE SI-29},
	isbn = {0002-7863},
	url = {<Go to ISI>://000169803000018},
	author = {Fyfe, C. A. and Brouwer, D. H. and Lewis, A. R. and Chezeau, J. M.}
}
@article {4550,
	title = {A comparison of NMR distance determinations in the solid state by cross polarization, REDOR, and TEDOR techniques},
	journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie},
	volume = {77},
	number = {11},
	year = {1999},
	note = {ISI Document Delivery No.: 253FETimes Cited: 14Cited Reference Count: 64},
	month = {Nov},
	pages = {1984-1993},
	type = {Article},
	abstract = {Solid-state NMR distance determinations using Hartmann-Hahn cross polarization between spin-1/2 nuclei (F-19/Si-29) are reported. F-19 {\textendash}> Si-29 polarization transfer for the T-1 silicon site in the clathrasil octadecasil shows an oscillatory behaviour as a function of the contact time. These oscillations were observed for non-spinning powder samples and also for different spinning speeds at the various MAS sideband matching conditions. Three analytical functions that allow efficient nonlinear least-square regression analyses of the experimental data to determine the internuclear distances for non-spinning powder samples as well as at the +/-1 and +/-2 MAS sideband matching conditions are reported. Using these functions, a F-19-Si-29 distance of 2.53 +/- 0.04 Angstrom was determined for the T-1 silicon in octadecasil from fitting of the oscillatory behaviour. This distance is in good agreement with that known from the X-ray structure and the previous F-19/Si-29 REDOR and TEDOR distance measurements. The advantages and limits of the different dipolar-based NMR techniques for heteronuclear distance determinations are examined and discussed.},
	keywords = {ANGLE-SPINNING NMR, cross polarization (CP), DISTANCE, distances F-19-Si-29, HELICAL PEPTIDE, HETERONUCLEAR DIPOLAR, interactions, INTERATOMIC, LOCK, NMR distance measurements, NUCLEAR-MAGNETIC-RESONANCE, octadecasil, PROTON-ENHANCED NMR, REDOR, ROTATIONAL-ECHO, SEQUENCES, SPIN-1/2 NUCLEI, TEDOR, TRANSIENT OSCILLATIONS},
	isbn = {0008-4042},
	url = {<Go to ISI>://000083545300032},
	author = {Fyfe, C. A. and Lewis, A. R. and Chezeau, J. M.}
}
@article {3042,
	title = {INCREASED EFFICIENCY OF COHERENCE TRANSFER IN CROSS-POLARIZATION NMR FROM QUADRUPOLAR NUCLEI - DYNAMIC-ANGLE CROSS-POLARIZATION},
	journal = {Journal of Physical Chemistry},
	volume = {98},
	number = {8},
	year = {1994},
	note = {ISI Document Delivery No.: MY355Times Cited: 9Cited Reference Count: 26},
	month = {Feb},
	pages = {2139-2142},
	type = {Article},
	abstract = {In this work we describe the increased efficiency obtained in solid-state coherence-transfer NMR experiments involving quadrupolar nuclei by carrying out cross-polarization while the sample is spinning along an axis parallel to the magnetic field. After the cross-polarization step, the spinning axis is rapidly switched to the {\textquoteright}{\textquoteright}magic angle{\textquoteright}{\textquoteright} for detection of a high-resolution free induction decay from the target nuclei. The increased efficiency of the cross-polarization process, coupled with the superior resolution available from magic-angle sample spinning, is useful for obtaining high-resolution NMR spectra of slowly-relaxing spin species in condensed phases. A specific example illustrating this method is drawn from the cross-polarization of magnetization from aluminum-27 spins to phosphorus-31 spins in the large-pore aluminophosphate VPI-5.},
	keywords = {DOUBLE-RESONANCE NMR, MOLECULAR-SIEVE VPI-5, PROTON-ENHANCED NMR, SOLIDS},
	isbn = {0022-3654},
	url = {<Go to ISI>://A1994MY35500028},
	author = {Fyfe, C. A. and Wongmoon, K. C. and Grondey, H. and Mueller, K. T.}
}
