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Predicting the NMR Spectra of Paramagnetic Molecules by DFT: Application to Organic Free Radicals and Transition‐Metal Complexes
Author(s) -
Rastrelli Federico,
Bagno Alessandro
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200802443
Subject(s) - paramagnetism , chemistry , chemical shift , spectral line , molecule , context (archaeology) , relaxation (psychology) , open shell , transition metal , nmr spectra database , computational chemistry , chemical physics , condensed matter physics , physics , organic chemistry , psychology , paleontology , social psychology , astronomy , biology , catalysis
Nuclear shieldings, including the Fermi contact and pseudocontact terms, have been calculated with DFT methods in a variety of open‐shell molecules (nitroxides, aryloxyl and various transition‐metal complexes), thereby predicting 1 H and 13 C chemical shifts. In general, when experimental data are reliable a good agreement with experimental values is observed, thus demonstrating the predictive power of DFT also in this context. However, the general accuracy is lower than that for closed‐shell species. A few inconsistencies in literature values are reconciled by reassigning some shifts. Structural, magnetic, and dynamic parameters have also been put into the Solomon–Bloembergen equations to predict signal line shapes, in particular those of signals that are difficult to locate or are undetectable. Guidelines are provided to predict the order of magnitude of relaxation rates. It is shown that DFT‐predicted paramagnetic shifts can greatly assist in obtaining and understanding the NMR spectra of paramagnetic molecules, which generally require different experimental strategies and exhibit problems in detection and assignment.