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Nuclear magnetic resonance shift reagents. Question of the orientation of the magnetic axis in lanthanide-substrate complexes

Hawkes, Geoffrey E. and Leibfritz, Dieter and Roberts, Donald W. and Roberts, John D. (1973) Nuclear magnetic resonance shift reagents. Question of the orientation of the magnetic axis in lanthanide-substrate complexes. Journal of the American Chemical Society, 95 (5). pp. 1659-1661. ISSN 0002-7863. doi:10.1021/ja00786a050. https://resolver.caltech.edu/CaltechAUTHORS:20151009-133523899

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Abstract

The utility of nmr shift reagents which function predominantly by the dipolar mechanism for structural and stereochemical problems is becoming abundantly clear. After a brief flurry of reports which indicated that the magnitude of the shifts induced by lanthanide chelates could be satisfactorily correlated by distance factors alone, the importance of angular factors, as predicted by the expected proportionality of the shifts to (3 cos^2 χ - 1) /r^3 , which would lead to either upfield or downfield shifts with the same reagent-substrate complex, has been clearly established. The (3 cos^2 χ - 1)/r^3 dependence, where χ is the angle between the principal magnetic axis of the complex and the vector of length, r, connecting the metal atom and nucleus under consideration, is justified strictly only for axially symmetric, or effectively axially symmetric, complexes. Nonetheless, excellent fits have been obtained following (3 cos^2 χ - 1)/r^3 proportionality with complexes of shift reagents and alcohols which can hardly be expected to be strictly axially symmetric and, furthermore, with the assumption that χ is, in fact, the angle between the vector r and the O-metal bond of the complex.


Item Type:Article
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http://dx.doi.org/10.1021/ja00786a050DOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja00786a050PublisherArticle
Additional Information:© 1973 American Chemical Society. Received June 27, 1972. Supported by the National Science Foundation and the Public Health Service, Research Grant No. GM-11072 from the Division of General Medical Sciences.
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Funding AgencyGrant Number
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U.S. Public Health Service (USPHS)GM-11072
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Caltech Gates and Crellin Laboratories of Chemistry4482
Issue or Number:5
DOI:10.1021/ja00786a050
Record Number:CaltechAUTHORS:20151009-133523899
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151009-133523899
Official Citation:Nuclear magnetic resonance shift reagents. Question of the orientation of the magnetic axis in lanthanide-substrate complexes Geoffrey E. Hawkes, Dieter Leibfritz, Donald W. Roberts, and John D. Roberts Journal of the American Chemical Society 1973 95 (5), 1659-1661 DOI: 10.1021/ja00786a050
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60947
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:16 Oct 2015 01:31
Last Modified:10 Nov 2021 22:42

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