@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 {7240,
	title = {HIGH-RESOLUTION C-13 AND N-15 NMR INVESTIGATIONS OF THE MECHANISM OF THE CURING REACTIONS OF CYANATE-BASED POLYMER RESINS IN SOLUTION AND THE SOLID-STATE},
	journal = {Macromolecules},
	volume = {25},
	number = {23},
	year = {1992},
	note = {ISI Document Delivery No.: JX890Times Cited: 43Cited Reference Count: 22},
	month = {Nov},
	pages = {6289-6301},
	type = {Article},
	abstract = {The mechanism of the curing reactions of cyanate polymer resins based on Bisphenol A dicyanate has been investigated both in solution and in the solid state by NMR spectroscopic techniques. To increase S/N and to unambiguously characterize the reactions of the cyanate functionalities, C-13- and N-15-enriched cyanate resins and monocyanate model compounds were used, the latter yielding soluble and isolable analogs. In solution, the main reaction is formation of triazine rings as identified by NMR and MS techniques and characterized by single-crystal X-ray diffraction on an isolated crystalline compound from the monocyanate model compound. Side products are formed by the reaction of the cyanate functionalities with trace water present in the solvent but there is no NMR evidence for the formation of dimeric or other intermediate species prior to triazine ring formation. The isolated resins from the solution curing and also those formed directly by heat curing of the neat resin were characterized by high-resolution solid-state NMR. In the former case triazine ring formation and the presence of side products were confirmed by both C-13 and N-15 solid-state NMR and their proportions quantified. In the case of the neat resin, the curing reaction is shown to be almost quantitative. This is rationalized in terms of the very strong intermolecular intercyanate bonding interactions observed in the crystal structure of the Bisphenol A dicyanate monomer obtained from a single-crystal X-ray diffraction experiment.},
	keywords = {MAGIC-ANGLE, NUCLEAR MAGNETIC-RESONANCE, SPECTRA},
	isbn = {0024-9297},
	url = {<Go to ISI>://A1992JX89000028},
	author = {Fyfe, C. A. and Niu, J. and Rettig, S. J. and Burlinson, N. E. and Reidsema, C. M. and Wang, D. W. and Poliks, M.}
}
