title: Dynamic nuclear polarization NMR spectroscopy of microcrystalline solids.
abstract: Dynamic nuclear polarization (DNP) solid-state NMR has been applied to powdered microcrystalline solids to obtain sensitivity enhancements on the order of 100. Glucose, sulfathiazole, and paracetamol were impregnated with bis-nitroxide biradical (bis-cyclohexyl-TEMPO-bisketal, bCTbK) solutions of organic solvents. The organic solvents were carefully chosen to be nonsolvents for the compounds, so that DNP-enhanced solid-state NMR spectra of the unaltered solids could be acquired. A theoretical model is presented that illustrates that for externally doped organic solids characterized by long spin-lattice relaxation times (T(1)((1)H) > 200 s), (1)H-(1)H spin diffusion can relay enhanced polarization over micrometer length scales yielding substantial DNP enhancements (ε). ε on the order of 60 are obtained for microcrystalline glucose and sulfathiazole at 9.4 T and with temperatures of ca. 105 K. The large gain in sensitivity enables the rapid acquisition of (13)C-(13)C correlation spectra at natural isotopic abundance. It is anticipated that this will be a general method for enhancing the sensitivity of solid-state NMR experiments of organic solids.
authors.affiliation: Centre de RMN a Tres Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1), 69100 Villeurbanne, France.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Rossini
authors.forename: Alexandre
authors.initials: A
authors.lastname: Zagdoun
authors.forename: Franziska
authors.initials: F
authors.lastname: Hegner
authors.forename: Martin
authors.initials: M
authors.lastname: Schwarzwälder
authors.forename: David
authors.initials: D
authors.lastname: Gajan
authors.forename: Christophe
authors.initials: C
authors.lastname: Copéret
authors.forename: Anne
authors.initials: A
authors.lastname: Lesage
authors.forename: Lyndon
authors.initials: L
authors.lastname: Emsley