17O NMR and crystalline hydrates

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy
• Materials science
• Physical chemistry

Background:

• 2H NMR is commonly used for studying hydrate structure and dynamics.
• Accurate determination of quadrupole coupling parameters is crucial for solid-state NMR.
• 17O NMR offers complementary information to 2H NMR.

Purpose of the Study:

• To investigate the effects of large 17O quadrupole coupling on resonance frequency and cross-polarization.
• To determine the H2(17)O quadrupole coupling tensor in alpha-oxalic acid dihydrate.
• To compare the determined tensor with the hydrogen bonding structure.

Main Methods:

• 17O NMR spectroscopy on powders and a single crystal of oxalic acid dihydrate.
• Second-order perturbation theory for analyzing orientational dependence.
• Cross-polarization techniques to examine excitation of the central transition.
• Analysis of powder patterns and single-crystal spectra.

Main Results:

• The orientational dependence of the central transition frequency is accurately described by second-order perturbation.
• The H2(17)O quadrupole coupling tensor in alpha-oxalic acid dihydrate was determined.
• Distinct transformation properties allowed separation of chemical and quadrupole-induced shifts.
• Methods to mitigate spectral distortions in 17O NMR experiments were presented.

Conclusions:

• 17O NMR is a valuable tool complementary to 2H NMR for solid hydrate studies.
• The determined quadrupole coupling tensor provides insights into hydrogen bonding.
• The study validates theoretical approximations and offers practical solutions for spectral analysis.