High resolution heteronuclear correlation NMR spectroscopy between quadrupolar nuclei and protons in the solid state

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Materials Science
• Quantum Information Science

Background:

• Solid-state NMR is crucial for characterizing materials at the atomic level.
• Correlating different nuclear spins enhances spectral resolution and information content.
• Half-integer quadrupolar nuclei present unique challenges in NMR due to their complex interactions.

Purpose of the Study:

• To develop a high-resolution 2D solid-state NMR experiment correlating half-integer quadrupolar spins with protons.
• To demonstrate the utility of this new pulse sequence for site assignment of quadrupolar nuclei.
• To enable spectral editing for half-integer quadrupolar nuclei coupled to protons.

Main Methods:

• Implementation of a novel 2D solid-state NMR experiment utilizing a split-t1, FAM-enhanced MQMAS (Multiple-Quantum Magic-Angle Spinning) pulse scheme.
• Cross-polarization (CP) for magnetization transfer from quadrupolar nuclei to protons during a mixing time.
• Detection of high-resolution proton signals under wPMLG5* homonuclear decoupling.

Main Results:

• Successful demonstration of the experiment on a sodium citrate powder sample.
• Acquisition of 23Na-1H 2D correlation spectra.
• Assignment of three crystallographically inequivalent Na+ sites using HETCOR (Heteronuclear Correlation) and MQMAS spectra.

Conclusions:

• The developed MQMAS-wPMLG HETCOR pulse sequence effectively correlates half-integer quadrupolar nuclei with protons.
• This method provides valuable insights for assigning quadrupolar nuclei sites in solid materials.
• The technique offers a powerful tool for spectral editing in complex solid-state NMR studies.