Rigid Orthogonal Bis-TEMPO Biradicals with Improved Solubility for Dynamic Nuclear Polarization

Eric L. Dane , Bjoern Corzilius , Egon Rizzato (1) , Pierre Stocker (2) , Thorsten Maly , Albert A. Smith , Robert G. Griffin , Olivier Ouari (2) , Paul Tordo (1) , Timothy M. Swagert

1 ICR - Institut de Chimie Radicalaire
2 LCP - Laboratoire Chimie Provence

The synthesis and characterization of oxidized bis-thioketal-trispiro dinitroxide biradicals that orient the nitroxides in a rigid, approximately orthogonal geometry are reported. The biradicals show better performance as polarizing agents in dynamic nuclear polarization (DNP) NMR experiments as compared to biradicals lacking the constrained geometry. In addition, the biradicals display improved solubility in aqueous media due to the presence of polar sulfoxides. The results suggest that the orientation of the radicals is not dramatically affected by the oxidation state of the sulfur atoms in the biradical, and we conclude that a biradical polarizing agent containing a mixture of oxidation states can be used for improved solubility without a loss in performance.

Domaines: Chimie

Eric L. Dane, Bjoern Corzilius, Egon Rizzato, Pierre Stocker, Thorsten Maly, et al.. Rigid Orthogonal Bis-TEMPO Biradicals with Improved Solubility for Dynamic Nuclear Polarization. Journal of Organic Chemistry, 2012, 77 (4), pp.1789--1797. ⟨10.1021/jo202349j⟩. ⟨hal-01460364⟩