@article {450, title = {Structural investigation of Silicalite-I loaded with n-hexane by X-ray diffraction, Si-29 MAS NMR, and molecular modeling}, journal = {Chemistry of Materials}, volume = {14}, number = {5}, year = {2002}, note = {ISI Document Delivery No.: 555JCTimes Cited: 23Cited Reference Count: 25}, month = {May}, pages = {2192-2198}, type = {Article}, abstract = {{The room temperature (298 K) structure of zeolite Silicalite-I loaded with approximately eight n-hexane molecules per unit cell was solved from twinned single-crystal X-ray diffraction (XRD) data in the monoclinic space group P12(1)/n1 with a = 19.8247(2) Angstrom}, keywords = {ADSORPTION, ALKANES, ENERGY-MINIMIZATION CALCULATIONS, LOCALIZATION, NAPHTHALENE, ORTHORHOMBIC FRAMEWORK, POWDER DIFFRACTION, SIMULATIONS, ZEOLITE H-ZSM-5, ZSM-5}, isbn = {0897-4756}, url = {://000175790100041}, author = {Morell, H. and Angermund, K. and Lewis, A. R. and Brouwer, D. H. and Fyfe, C. A. and Gies, H.} } @article {4813, title = {Solid-state NMR and X-ray diffraction structural investigations of the p-nitroaniline/ZSM-5 complex}, journal = {Microporous and Mesoporous Materials}, volume = {39}, number = {1-2}, year = {2000}, note = {ISI Document Delivery No.: 354ZKTimes Cited: 15Cited Reference Count: 19}, month = {Sep}, pages = {291-305}, type = {Article}, abstract = {The complex of zeolite ZSM-5 loaded with p-nitroaniline to four molecules per unit cell is of current interest as a potential non-linear optical material. A previous single crystal X-ray diffraction (XRD) investigation has claimed that the p-nitroaniline molecules line up as oriented dipole chains inside the channels of ZSM-5, and it was concluded that this ordering explains how second harmonic generation arises. In another XRD study, it was not possible to distinguish between order and disorder of the p-nitroaniline molecules. The present results from solid-state NMR and single crystal XRD experiments indicate that the p-nitroaniline molecules are disordered in the ZSM-5 channels, i.e., they do not form ordered dipole chains throughout the entire crystal. The quantitative Si-29-MAS spectrum at room temperature shows 48 peaks of equal intensity indicating disorder of the guest molecules, and the N-15-MAS spectrum at 180 K of the N-15-labeled p-nitroaniline in ZSM-5 shows a splitting of the NO2 resonance, which also implies disorder. The single crystal XRD results show that the p-nitroaniline molecules are disordered over four-sites at the channel intersection even when refined in the less symmetric Pn2(l)a space group. The final structure was refined in the orthorhombic Pnma space group to R = 0.0465. The nature of this disorder is discussed. In particular, the possibilities of disorder arising from the average of polar domains or local disorder are examined in the light of the solid-state NMR results. That the p-nitroaniline molecules are disordered in ZSM-5 implies that the mechanism by which second harmonic generation arises may be more complex than is presently assumed. (C) 2000 Elsevier Science B.V. All rights reserved.}, keywords = {CRYSTAL STRUCTURE-ANALYSIS, DICHLOROBENZENE, harmonic generation, LOCATION, MFI, MOLECULAR-SIEVE, p-nitroaniline, second, SINGLE-CRYSTAL, SOLID-STATE NMR, x-ray diffraction, ZEOLITE H-ZSM-5, ZSM-5}, isbn = {1387-1811}, url = {://000089361000029}, author = {Fyfe, C. A. and Brouwer, D. H.} } @article {7023, title = {THE COMBINATION OF SYNCHROTRON POWDER DIFFRACTION AND HIGH-RESOLUTION SOLID-STATE NMR EXPERIMENTS}, journal = {Journal of Physics and Chemistry of Solids}, volume = {52}, number = {10}, year = {1991}, note = {ISI Document Delivery No.: GU763Times Cited: 18Cited Reference Count: 22}, pages = {1235-1241}, type = {Article}, abstract = {Structural investigations on three zeolites, ZSM-11, ZSM-12 and ZSM-5, have been carried out by a combination of high-resolution solid-state Si-28 NMR experiments and Rietveld refinement of synchrotron X-ray powder data. These techniques, being sensitive to short- and long-range order, respectively, gave a most complete picture of the structure of the solid state. Variable temperature NMR experiments of ZSM-11 revealed a displacive phase transition with a change in symmetry at about 300 K. A Rietveld refinement of a data set recorded at 373 K confirmed the proposed structure model. The structure of ZSM-12 was refined from room temperature synchrotron powder data. Space group ambiguities because of pseudo-symmetry of the silica framework of the zeolite were resolved with the aid of Si-29 NMR experiments leading to C2/c as the true space group symmetry. Si-29 NMR and X-ray studies of ZSM-5 showed that the symmetry of the crystal structure depends on the temperature, the concentration of the guest molecule, and on the number of Al atoms in the framework. A full pattern refinement of silica-ZSM-5 loaded with two molecules p-dichlorobenzene per unit cell showed that the site occupied by the sorbed molecule is not at the intersection of the channels but shifted by 1/4 along b0.}, keywords = {3-DIMENSIONAL LATTICE CONNECTIVITIES, CRYSTAL-STRUCTURE, ORTHORHOMBIC FRAMEWORK, Rietveld refinement, Si-29 NMR, SINGLE-CRYSTAL, SORBATE, ZEOLITE H-ZSM-5, zeolites, ZSM-11, ZSM-12, ZSM-5}, isbn = {0022-3697}, url = {://A1991GU76300006}, author = {Gies, H. and Marler, B. and Fyfe, C. and Kokotailo, G. and Feng, Y. and Cox, D. E.} }