Lanthanide shift reagents applications

Paramagnetic lanthanide shift reagents in n.m.r. spectroscopy principles methodology and applications. J. Reuben, Prog. Nucl. Magn. Reson. Spectrosc., 1973, 9, 3-70 (280). 

In 2-substituted adamantanes 25 both types of 8-positioned carbon atoms (8syn and 8 ) exist within one molecule (Scheme 37). Early measurements with limited spectral resolution (176) did not differentiate between their signals. Later (124,244), differences of up to 0.7 ppm were detected, and application of various independent methods, including addition of lanthanide shift reagents (245), determination of longitudinal relaxation times T, (246), and evaluation of deuterium... 

The fundamentals and applications of NMR spectroscopy in the presence of lanthanide shift reagents (LSR) have been reviewed in a number of articles237-244. Hence, only a brief introduction is warranted in this section. 

The two major applications of lanthanide shift reagents are firstly the simplification of the spectrum, and secondly the confirmation of the assignment of signals by relating the extent of the shift to the concentration of the shift reagent. 

Lanthanide shift reagents have been used to study dynamic NMR processes. One of the classic applications involves the study of rotational barriers of various amides " thioamides ", oximes " and amide oximes ". Lanthanide-induced shifts enabled the distinction of cis- and trans- or syn- and awri -isomers, and variable-temperature studies in the presence of the chelate were performed to determine the barrier to rotation. 

J. Reuben, in Progress in Nuclear Magnetic Resonance Speetroscopy , Vol. 9, Pt. 1 Lanthanide Shift Reagents m NMR Spectroscopy Principles, Methodology and Applications , Pergamon Press, Oxford, 1973. 

NMR spectroscopy used in conjunction with lanthanide shift reagents supports the application of LCAO-SCF calculations to 1,2,4-triazoles (74JOC357). 

Steroid Properties and Reactions (Chapter 1).— The application of modem computing techniques to valence-force calculations marks a new phase in the conformational analysis of steroids. This approach brings within reach the accurate specification of preferred conformations, and the evaluation of conformational energies and conformational transmission effects and thus promises to complement the chemical and physical techniques used hitherto. The introduction of lanthanide shift reagents in n.m.r. spectroscopy promises to be particularly valuable in the analysis of steroids since it overcomes to a large extent a major limitation, namely the near-equivalence of many protons attached to the steroid nucleus. Further useful advances in applying solvent shifts... 

In concluding this Section of this article, it is appropriate to mention that lanthanide shift-reagents have already had an enormous impact on the field of high-resolution, n.m.r. spectroscopy of organic molecules, and it is surprising that, up until March, 1973, there have been only nine applications reported in the carbohydrate doubtless,... 

Examples of applications of shift or relaxation measurements 39.Z9.5 Studies of complexation with lanthanide shift reagents... 

Smith et have prepared 11 chiral calix[4]arenes, calix[4]resorcarenes, and anionic cyclodextrin derivatives and investigated the properties of their lanthanide (Yb, Dy +) complexes as chiral lanthanide shift reagents (LSR). Baldovini et alP report an application of a camphor-derived chiral complex, Yb(hfc)3 (hfc = tris[3-(heptafluoropropylhydroxymethylene)-(- -)-camphorate]) to differentiate the C NMR spectra of enantiomers of bornyl acetate. 

More detailed accounts of the applications and limitations of the lanthanides as structural elucidation aids have appeared [27,28]. From studies of the mitogenic responses of lymphocytes in the presence of lanthanide shift reagents, Sze et al. [29] recently concluded that they should not be regarded as physiologically harmless reagents. In addition, Boulanger et al. [30] recently carried out an extensive investigation of the effects of dysprosium tripolyphosphate and dysprosium triethylenetriamine-hexaacetate (TTHA) on several cells. 

Geology, Geochemistry, and Natural Abundances of the Rare Earth Elements Lanthanide Complexes with Mul-tidentate Ligands Lanthanides Luminescence Applications Lanthanide Shift Reagents. 

Reuben J 1973 Paramagnetic lanthanide shift reagents in NMR spectroscopy principles, methodology and applications. Prog Nuc Magn Res Spec 9 1-70... 

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