Effects of biradical deuteration on the performance of DNP: towards better performing polarizing agents

Abstract

We study the effects of the deuteration of biradical polarizing agents on the efficiency of dynamic nuclear polarization (DNP) via the cross-effect. To this end, we synthesized a series of bTbK and TOTAPol biradicals with systematically increased deuterium substitution. The deuteration increases the radicals' relaxation time, thus contributing to a higher saturation factor and larger DNP enhancement, and reduces the pool of protons within the so-called spin diffusion barrier. Notably, we report that full or partial deuteration leads to improved DNP enhancement factors in standard samples, but also slows down the build-up of hyperpolarization. Improvements in DNP enhancements factors of up to 70% and time savings of up to 38% are obtained upon full deuteration. It is foreseen that this approach may be applied to other DNP polarizing agents thus enabling further sensitivity improvements.

High resolution observed in 800 MHz DNP spectra of extremely rigid type III secretion needles

“…This can be achieved by searching for different sample preparation protocols rather than using the established glycerol matrix (Liao et al 2016;Takahashi et al 2013) and by searching for biradicals that allow reasonable enhancement factors at higher temperatures (Lelli et al 2015;Perras et al 2016).…”

Dendritic polarizing agents for DNP SENS

“…From allylbenzyl ether, D1 was built by repetitive hydrosilylation with (dichloro)phenylsilane catalyzed by Karstedt's catalyst 48 followed by reaction with allylmagnesium bromide. Trideuteriomethyl-magnesium iodide (CD 3 MgI) was used to install the end groups to prevent fast electron and nuclear relaxations promoted by the rotations of methyl groups (–CH 3 ) at 100 K. 25,49,50 The benzyl group was then removed by homogeneous oxidative cleavage to generate the OH anchor group (Scheme 2b). We note that the typical Pd/C catalyzed reductive cleavage failed, suggesting the inaccessibility of the benzyl ether on the dendrimer to the Pd/C surface.…”

In Silico Design of DNP Polarizing Agents: Can Current Dinitroxides Be Improved?

“…At this condition, ac ross-effect event can occur involving the simultaneousf lip of the two electrons and the nuclear spin, leading to the hyperpolarization of the nuclear spin. [29,30] Recently,G riffin's group has presented trityl-TEMPO biradicals, coined TEMtriPols, in which the trityl radical is most easily saturated due to its low ga nisotropy,l eading to an improved DNP efficiency,p articularly at high magnetic fields. Generally,a ny condition in which the g yy tensorc omponents of both radicals are perpendicular to one anotheri s expectedt oh ave near-optimal DNP performance.…”