Molecular Dynamics and Hyperpolarization Performance of Deuterated β-Cyclodextrins

Area of Science:

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

Background:

• Nuclear spin-lattice relaxation rate (1/T1) and dynamic nuclear polarization (DNP) are crucial parameters in NMR spectroscopy.
• β-cyclodextrins are versatile host molecules with potential applications in molecular imaging.
• Understanding the temperature dependence of relaxation and DNP is key to optimizing NMR performance.

Purpose of the Study:

• To investigate the temperature dependence of 1H and 13C nuclear spin-lattice relaxation rates and DNP performance in deuterated β-cyclodextrins.
• To analyze the mechanisms governing nuclear spin polarization buildup and relaxation below 4.2 K.
• To explore the impact of deuteration on relaxation times and NMR spectral line widths.

Main Methods:

• Measurement of temperature-dependent 1/T1 for 1H and 13C nuclei.
• Evaluation of dynamic nuclear polarization (DNP) performance.
• Analysis of nuclear spin polarization buildup rates.
• Investigation of the thermal mixing regime and glassy dynamics.
• NMR spectral line width analysis.

Main Results:

• Achieved up to 10% 13C DNP-enhanced polarization.
• Observed temperature dependence of 1/T1 influenced by glassy dynamics at low temperatures and molecular motions at high temperatures.
• Demonstrated relaxation times approaching 30 s at room temperature due to deuteration.
• Identified deviations from theoretical behavior in the thermal mixing regime below 4.2 K.

Conclusions:

• Deuteration of methyl groups in β-cyclodextrins significantly enhances DNP performance and relaxation times.
• The material exhibits promising properties for molecular imaging applications due to extended relaxation times at room temperature.
• Molecular dynamics play a critical role in determining relaxation behavior and NMR spectral line widths.