Optimization and prediction of the electron–nuclear dipolar and scalar interaction in¹H and¹³C liquid state dynamic nuclear polarization

Abstract

Solution-state dynamic nuclear polarization (DNP) is a powerful tool for hyperpolarization and the study of intermolecular interactions in solution.

Dynamic Nuclear Polarization of 13C Nuclei in the Liquid State over a 10 Tesla Field Range

“…The capability of determining enhancements as well as s and f independently up to 9.4 Tesla (Supporting Information) offers the opportunity to draw a quantitative picture of the 13 C DNP mechanism. Plots of ξ from Equation (1) as a function of the static magnetic field are displayed in Figure a–c together with the literature data at 0.34 and 3.4 T ,. Notably, | ξ | of 13 CCl 4 increases with field and reaches a maximum value at around 3 T, while | ξ | of 13 CHCl 3 decreases almost monotonously from low to high fields (Figure a,b).…”

“…The field dependence of 13 C‐DNP was analyzed for the three compounds doped with TN, that is, 13 CCl 4 , 13 CHCl 3 , and 13 C‐2 diethyl malonate ,. The enhancements, summarized in Figure , show a very weak field dependence.…”

Spin density localization and accessibility of organic radicals affect liquid-state DNP efficiency

“…In the first step, we computed the spin density distribution for each radical optimized structure to identify the radical sites in each PA. In NODs, the electron spin density is almost completely localized on the NO group 38,45 (B90% of the Löwdin spin population, Fig. 3a).…”

“…Despite the available data, it is difficult to compare the PA's performance independently of the experimental conditions, such as mw power and resonant cavity, magnetic field, radical concentration, and target nuclei. Although several mechanistic studies on 1 H 27,35,36 and 13 C 24,37,38 have been reported, the detailed role of the PA remains unclear. Very recently, we investigated the case of fullerene nitroxides in comparison to TEMPONE, 24,39 and found that small structural reorientations can impact the DNP efficiency at both low and high magnetic fields.…”

“…In a second step, we considered the static complex PA/target molecule and used DFT calculations to compute the hyperfine coupling constant A FC to the target nucleus. 38,42 A FC of the C nucleus in CHCl 3 was calculated for at least four optimized geometries i for each complex PA/CHCl 3 (ESI †). Due to the tendency of the H atom of CHCl 3 to form hydrogen bonds, we distinguish an energetically favoured complex where the H is pointing towards the radical (''via H''), and a less favoured one, where the Cl atom is the closest to the radical (''via Cl'').…”