C. Gaellieri et al., Dynamic Nuclear Polarization with Polychlorotriphenylmethyl Radicals: Supramolecular Polarization-Transfer Effects, Angew. Chem. Int. Ed., 2010, 49, 3360-3362
Polychlorinated trityl radicals (see structure: C black, Cl green, Na gray, O red) used for dynamic nuclear polarization (DNP) showed a new transfer mechanism involving quadrupolar chlorine nuclei. The observation of positive or negative enhancements, depending on the substrate, highlights the supramolecular character of the initial polarization-transfer process.