From The DNP-NMR Blog:
Dynamic nuclear polarization NMR enables the analysis of sn-Beta zeolite prepared with natural abundance (119)sn precursors
Gunther, W.R., et al., Dynamic nuclear polarization NMR enables the analysis of sn-Beta zeolite prepared with natural abundance (119)sn precursors. J Am Chem Soc, 2014. 136(17): p. 6219-22.
http://www.ncbi.nlm.nih.gov/pubmed/24697321
<div style="text-align: justify;">The catalytic activity of tin-containing zeolites, such as Sn-Beta, is critically dependent on the successful incorporation of the tin metal center into the zeolite framework. However, synchrotron-based techniques or solid-state nuclear magnetic resonance (ssNMR) of samples enriched with (119)Sn isotopes are the only reliable methods to verify framework incorporation. This work demonstrates, for the first time, the use of dynamic nuclear polarization (DNP) NMR for characterizing zeolites containing approximately 2 wt % of natural abundance Sn without the need for (119)Sn isotopic enrichment. The biradicals TOTAPOL, bTbK, bCTbK, and SPIROPOL functioned effectively as polarizing sources, and the solvent enabled proper transfer of spin polarization from the radical's unpaired electrons to the target nuclei. Using bCTbK led to an enhancement (epsilon) of 75, allowing the characterization of natural-abundance (119)Sn-Beta with excellent signal-to-noise ratios in