Investigation of slow molecular dynamics using R-CODEX

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.
• Materials science and dynamics characterization.

Background:

• Probing molecular motions on the millisecond timescale is crucial for understanding complex dynamic processes.
• Existing methods may face challenges with sensitivity or applicability to fully protonated samples.

Purpose of the Study:

• To introduce a novel solid-state NMR experiment for characterizing millisecond-timescale dynamics.
• To enable the measurement of both correlation times and reorientational angles of molecular motion.
• To overcome limitations of previous techniques, particularly in highly protonated systems.

Main Methods:

• Development of a new solid-state NMR pulse sequence based on dephasing and refocusing of (1)H-(13)C or (1)H-(15)N dipolar couplings.
• Utilization of an R-type dipolar recoupling sequence to leverage strong heteronuclear couplings.
• Suppression of interfering (1)H-(1)H homonuclear couplings.

Main Results:

• The new experiment successfully probes motions on the millisecond timescale.
• The method demonstrates the ability to determine correlation times and reorientational angles.
• Effective suppression of homonuclear couplings was achieved, enhancing signal quality.
• The pulse sequence performance was validated using imidazole methyl sulfonate.

Conclusions:

• The introduced solid-state NMR experiment provides a powerful tool for studying millisecond dynamics.
• This method offers a significant advancement for characterizing molecular motion in challenging, fully protonated samples.
• The technique enhances the scope of NMR spectroscopy in dynamics studies.