Nature of paramagnetic shifts initiated by lanthanide shift reagents

Conclusions A mechanism was proposed that explains the additional paramagnetic shifts that are induced by lanthanide shift reagents in the NMR spectra (except¹H), which are caused by the anisotropy of the shielding tensor of the resonating nucleus.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 423–424, February, 1977.     

PMR configurational analysis of pinitol with the aid of lanthanide shift reagents and the homonuclear INDOR technique

The PMR spectrum of the peracetylated O-methyl-chiro-inositol (pinitol) could be analysed by employing lanthanide shift reagents and performing spin-decoupling and INDOR experiments. The 100 MHz theoretical spectrum has been simulated and good agreement with the experiment has been achieved. Analysis of the vicinal H? H-couplings yields the relative configuration.     

Ligand conformation in lanthanide complexes by NMR paramagnetic shifts: L-proline and L-valine

A fitting procedure is descdribede to establish the conformation and molecular dynamics of flexible molecules co-ordinated to lanthanide cations from NMR paramagnetic shift data of ¹H and ¹³C resonances. The results from L -proline and L -valine in aqueous solution at low pH values are consistent with peak assignments given by independent methods. A free rotation of the pyrrolidine ring is proposed in the case of L -proline, and a rigid lock in the case of L -valine, and angle and distance values are given for the cation and ligand positions in the complex.     

Atropo-isomerism and abnormal temperature dependence of paramagnetic shifts in 1H NMR spectra of heterocyclic analogs of isoflavones in the presence of lanthanide chelates

It has been found that spatially hindered analogs of isoflavones can occur as a mixture of atropo-isomers, which is conveniently detected by using optically active lanthanide shift reagents. It is shown that on lowering the temperature the individual shifts of the signals of the isoflavone protons can either increase or decrease. The observed anomalies are attributed to changes in the predominant conformations of the molecules as the temperature is varied.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 629–633, September–October, 1989.     

Sulfonium salts as lanthanide shift donors in PMR amd CMR spectroscopy

Lanthanide shift reagents (LSR) may be used in the structural elucidation of sulfonium salts by both PMR and CMR. In these investigations there is qualitative agreement with the McConnel-Robertson equation and complexatlon appears to occur at the anion.     

Effect of lanthanide shift reagents on conformational equilibria

The conformational equilibrium constants for a series of 1-alkyl substituted cyclohexanols have been determined using a lanthanide shift reagent, and the results compared with other methods. In comparison to other technique greater preference is shown by the hydroxyl group for the equatorial position. This is rationalized by the effect on the equilibrium of the bulky shift reagent.     

重水溶液中稀土-吡啶-2,6-二羧酸配合物的第二配位圈^1HNMR顺磁位移

对稀土-吡啶-2,6-二羧酸(DPA)配合物Ln(DPA)3进行了NMR研究并观察到了由溶剂分子形成的第二配位圈的顺磁位移效应.