Háskóli ÍslandsUniversity of IcelandHarrabi, RaniaHalbritter, ThomasAlarab, ShadiChatterjee, SatyakiWolska-Pietkiewicz, MalgorzataDamodaran, Krishna K.van Tol, JohanLee, DanielPaul, SubhradipHediger, SabineSigurdsson, Snorri Th.Mentink-Vigier, FredericDe Paëpe, Gaël2025-03-072025-03-072024Harrabi, R. et al. (2024). AsymPol-TEKs as efficient polarizing agents for MAS-DNP in glass matrices of nen-aqueous solvents. Physical Chemistry Chemical Physics;26(6), 5669-5682. DOI:10.1039/d3cp04271e1463-90761463-9084https://hdl.handle.net/20.500.11815/5390Two polarizing agents from the AsymPol family, AsymPol-TEK and cAsymPol-TEK (methyl-free version) are introduced for MAS-DNP applications in non-aqueous solvents. The performance of these new biradicals is rationalized in detail using a combination of Electron Paramagnetic Resonance spectroscopy, Density Functional Theory, Molecular Dynamics and quantitative MAS-DNP spin dynamics simulations. By slightly modifying the experimental protocol to keep the sample temperature low at insertion, we are able to obtain reproducable DNP-NMR data with 1,1,2,2-tetrachloroethane (TCE) at 100 K, which facilitates optimization and comparison of different polarizing agents. At intermediate magnetic fields, AsymPol-TEK and cAsymPol-TEK provide 1.5 to 3-fold improvement in sensitivity compared to TEKPol, one of the most widely used polarizing agents for organic solvents, with significantly shorter DNP build-up times of ~ 1 s and ~ 2 s at 9.4 and 14.1 T respectively. In the course of the work, we also isolated and characterized two diastereoisomers that can form during the synthesis of AsymPol-TEK; their difference in performance is described and discussed. Finally, the advantages of the AsymPol-TEKs are demonstrated by recording 2D 13C-13C correlation experiments at natural 13C-abundance of proton-dense microcrystals and by polarizing the surface of ZnO nanocrystals (NCs) coated with diphenyl phosphate ligands. For those experiments, cAsymPol-TEK yielded a three-fold increase in sensitivity compared to TEKPol, corresponding to a nine-fold time saving.5669-5682eninfo:eu-repo/semantics/openAccessEfnafræðiinfo:eu-repo/semantics/articlePhysical Chemistry Chemical Physics10.1039/d3cp04271e