Rigid orthogonal bis-TEMPO biradicals with improved solubility for dynamic nuclear polarization.
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.
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
Eric L
EL
Dane
Björn
B
Corzilius
Egon
E
Rizzato
Pierre
P
Stocker
Thorsten
T
Maly
Albert A
AA
Smith
Robert G
RG
Griffin
Olivier
O
Ouari
Paul
P
Tordo
Timothy M
TM
Swager
D003497:Cyclic N-Oxides / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010084:Oxidation-Reduction; D012995:Solubility; D013113:Spin Labels / Q000138:chemical synthesis*; D013454:Sulfoxides / Q000737:chemistry; D013455:Sulfur / Q000737:chemistry; D014867:Water
D003497:Cyclic N-Oxides; D013113:Spin Labels; D013454:Sulfoxides; D014867:Water; D013455:Sulfur