Molecular Dynamics and Hyperpolarization Performance of Deuterated β-Cyclodextrins.

We discuss the temperature dependence of the H and C nuclear spin-lattice relaxation rate 1/ T and dynamic nuclear polarization (DNP) performance in β-cyclodextrins with deuterated methyl groups. It is shown that C DNP-enhanced polarization is raised up to 10%. The temperature dependence of the buildup rate for nuclear spin polarization and of 1/ T, below 4.

Proton and Carbon-13 Dynamic Nuclear Polarization of Methylated β-Cyclodextrins.

H and C dynamic nuclear polarizations have been studied in C-enriched β-cyclodextrins doped with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl free radical. H and C polarizations raised above 7.5 and 7%, respectively, and for both nuclear species, the transfer of polarization from the electron spins appears to be consistent with a thermal mixing scenario for a concentration of 9 C nuclei per molecule.

Dynamic Nuclear Polarization of β-Cyclodextrin Macromolecules.

H dynamic nuclear polarization and nuclear spin-lattice relaxation rates have been studied in amorphous complexes of β-cyclodextrins doped with different concentrations of the TEMPO radical. Nuclear polarization increased up to 10% in the optimal case, with a behavior of the buildup rate (1/T) and of the nuclear spin-lattice relaxation rate (1/T) consistent with a thermal mixing regime. The temperature dependence of 1/T and its increase with the radical concentration indicate a relaxation process arising from the modulation of the electron-nucleus coupling by the glassy dynamics.

Evidence of spin-temperature in dynamic nuclear polarization: an exact computation of the EPR spectrum.

In dynamic nuclear polarization (DNP) experiments, the compound is driven out-of-equilibrium by the microwave (MW) irradiation of the radical electron spins. Their stationary state has been recently probed via electron double resonance (ELDOR) techniques showing, at low temperature, a broad depolarization of the electron paramagnetic resonance (EPR) spectrum under microwave irradiation. In this theoretical manuscript, we develop a numerical method to compute exactly the EPR spectrum in the presence of dipolar interactions.