期刊
JOURNAL OF MAGNETIC RESONANCE
卷 251, 期 -, 页码 36-42出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jmr.2014.11.013
关键词
Solid state NMR; Paramagnetic solid; 2D correlation spectra; Chemical shift assignment
资金
- National Natural Science Foundation of China [21373265, 21210005, 21221064]
- Region Nord/Pas de Calais, Europe (FEDER)
- CNRS [ANR-2010-jcjc-0811-01]
- Infrastructure of Research in Nuclear Magnetic Resonance (IR-NMR)
- Chinese Academy of Sciences
The assignment of NMR signals in paramagnetic solids is often challenging since: (i) the large paramagnetic shifts often mask the diamagnetic shifts specific to the local chemical environment, and (ii) the hyperfine interactions with unpaired electrons broaden the NMR spectra and decrease the coherence lifetime, thus reducing the efficiency of usual homo- and hetero-nuclear NMR correlation experiments. Here we show that the assignment of H-1 and C-13 signals in isotopically unmodified paramagnetic compounds with moderate hyperfine interactions can be facilitated by the use of two two-dimensional (2D) experiments: (i) H-1-C-13 correlations with H-1 detection and (ii) H-1-H-1 double-quantum <-> single-quantum correlations. These methods are experimentally demonstrated on isotopically unmodified copper (II) complex of L-alanine at high magnetic field (18.8 T) and ultra-fast Magic Angle Spinning (MAS) frequency of 62.5 kHz. Compared to C-13 detection, we show that H-1 detection leads to a 3-fold enhancement in sensitivity for H-1-C-13 2D correlation experiments. By combining H-1-C-13 and H-1-H-1 2D correlation experiments with the analysis of C-13 longitudinal relaxation times, we have been able to assign the H-1 and C-13 signals of each L-alanine ligand. (C) 2014 Elsevier Inc. All rights reserved.
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