Solid-state nuclear magnetic resonance study of the structure of lanthanum phosphate crystals and glasses

Lanthanum phosphate glasses were synthesized by melt quenching and characterized by x-ray diffraction, electron microprobe analysis, and solid-state nuclear magnetic resonance spectroscopy. A range of compositions near the metaphosphate composition (75 mol% P2O5) was examined. Comparison of 31P chemical shifts and shielding anisotropies of glasses with those of the crystalline phases of La(PO3)3 (metaphosphate) and LaP5O14 (pentaphosphate) were consistent with the presence of primarily chainlike Q2 phosphate groups.

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A carbon-13 nuclear magnetic resonance study of solid tetracyclines

Canadian Journal of Chemistry ◽

10.1139/v87-061 ◽

1987 ◽

Vol 65 (2) ◽

pp. 357-362 ◽

Cited By ~ 11

Author(s):

Sandra Mooibroek ◽

Roderick E. Wasylishen

Keyword(s):

Nuclear Magnetic Resonance ◽

Solid State ◽

Magnetic Resonance ◽

Pulse Sequence ◽

Chemical Shifts ◽

Nuclear Magnetic Resonance Study ◽

Magic Angle ◽

X Ray Diffraction ◽

Magic Angle Sample Spinning ◽

Nuclear Magnetic

Magic angle sample spinning and proton/carbon-13 cross-polarization techniques have been used to obtain high resolution solid state 13C nuclear magnetic resonance spectra of several tetracycline antibiotics. Carbon-13 resonances in the solid state are assigned by measuring the extent of dipolar broadening due to neighbouring quadrupolar nuclei and by using a pulse sequence that suppresses non-quaternary carbon resonances. The observed 13C chemical shifts are discussed in light of the known solid state structures derived from X-ray diffraction, and are compared with those in solution. It is shown that the solid state nuclear magnetic reosnance technique is capable of clearly distinguishing between the neutral and zwitterionic forms of the tetracycline free bases.

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A carbon-13 CP/MAS nuclear magnetic resonance study of several 1,4-disubstituted benzenes in the solid state

Canadian Journal of Chemistry ◽

10.1139/v89-080 ◽

1989 ◽

Vol 67 (3) ◽

pp. 525-534 ◽

Cited By ~ 16

Author(s):

Glenn H. Penner ◽

Roderick E. Wasylishen

Keyword(s):

Nuclear Magnetic Resonance ◽

Solid State ◽

Magnetic Resonance ◽

Chemical Shifts ◽

Substituent Effects ◽

Nuclear Magnetic Resonance Study ◽

Solution Studies ◽

Temperature Solution ◽

Cp Mas Nmr ◽

Nuclear Magnetic

The carbon-13 chemical shifts of several 1,4-disubstituted benzenes in the solid state are reported. At least one of the substituents is unsymmetrical and in most cases this leads to different 13C chemical shifts of C-2 and C-6 and in some cases to different shifts for C-3 and C-5. The 13C chemical shifts observed in the solid state are compared with those measured in solution and, where possible, with those obtained in low temperature solution studies where internal rotation of the unsymmetrical substituent is slow on the 13C chemical shift time scale. Agreement between the chemical shifts observed in the solid state and solution is excellent. The potential application of CP/MAS nuclear magnetic resonance in deducing the conformation of benzene derivatives with two unsymmetrical substituents is discussed. Keywords: carbon-13 CP/MAS NMR, 13C NMR chemical shifts, substituent effects.

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