H and 15N Dynamic Nuclear Polarization Studies of Carbazole

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 104; no. 19; pp. 4413 - 4420
• Main Authors: Hu, Jian Z, Solum, Mark S, Wind, Robert A, Nilsson, Brad L, Peterson, Matt A, Pugmire, Ronald J, Grant, David M
• Format: Journal Article
• Language: English
• Published: American Chemical Society 18.05.2000
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp9938011

15N NMR experiments, combined with dynamic nuclear polarization (DNP), are reported on carbazole doped with the stable free radical 1,3 bisdiphenylene-2-phenylallyl (BDPA). Doping shortens the nuclear relaxation times and provides paramagnetic centers that can be used to enhance the nuclear signal by means of DNP so that 15N NMR experiments can be done in minutes. The factors were measured in a 1.4 T external field, using both unlabeled and 98% 15N labeled carbazole with doping levels varying between 0.65 and 5.0 wt % BDPA. A doping level of approximately 1 wt % produced optimal results. DNP enhancement factors of 35 and 930 were obtained for 1H and 15N, respectively making it possible to perform 15N DNP NMR experiments at the natural abundance level.