Zero-point vibrational effects on proton shieldings: Functional-group contributions from ab initio calculations

Citation
K. Ruud et al., Zero-point vibrational effects on proton shieldings: Functional-group contributions from ab initio calculations, J AM CHEM S, 123(20), 2001, pp. 4826-4833
Citations number
50
Categorie Soggetti
Chemistry & Analysis",Chemistry
Journal title
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
ISSN journal
00027863 → ACNP
Volume
123
Issue
20
Year of publication
2001
Pages
4826 - 4833
Database
ISI
SICI code
0002-7863(20010523)123:20<4826:ZVEOPS>2.0.ZU;2-#
Abstract
We investigate the effects of zero-point vibrational motion on the nuclear magnetic shielding constants of a large number of organic molecules. The vi brational corrections include anharmonic contributions from the potential e nergy surface and harmonic contributions from the curvature of the property surface. Particular attention is paid to vibrational corrections to hydrog en shielding constants where we show that vibrational corrections may be su bstantial, ranging from about +0.50 to -0.70 ppm, and thus demonstrating th at ignoring these effects may give errors in the chemical shifts by more th an 1 ppm in certain extreme cases. These effects can therefore not be negle cted when comparing calculated results with experiment, not even for the ch emical shifts. However, we also demonstrate that the vibrational correction s to the hydrogen shieldings are to a large extent transferable from one mo lecule to another. We have tabulated functional vibrational corrections to the hydrogen shieldings, based on results for more than 35 molecules. Unfor tunately, no similar transferability has been observed for the vibrational corrections to shielding constants of other nuclei such as carbon, nitrogen , or oxygen.