Structural information from chemical shifts in lanthanide complexes

Reuben, Jacques

doi:10.1016/0022-2364(82)90053-1

Cited by 27 publications

(19 citation statements)

References 16 publications

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“…Three-nuclei-plot of Li[Ln(hdcCOT) 2 ] according to Reuben with linear fits for the individual positions. The Ho 3+ ion was chosen as reference, and parameter Y was calculated accordingly as Y Ln,i Ho = δ HF Ln,i (⟨ S Z ⟩ Ho /⟨ S Z ⟩ Ln ) – δ HF Ho,i .…”

Section: Resultsmentioning

confidence: 99%

“…There are a number of reports that show limitations of the applicability of Bleaneys theory, and the corresponding plots (see the Supporting Information) reveal that the compounds investigated herein are poorly described by Bleaney factors. , This is in line with recent ab initio calculations which have shown that the crystal field parameter B 4 0 is considerably large in [Ln(COT) 2 ] − complexes. The use of Bleaney factors can be avoided when more NMR data are available, leading to plots with the so-called “three-nuclei method” . Application of the latter gives excellent isostructurality plots for all positions (Figure ).…”

Section: Resultsmentioning

confidence: 99%

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Paramagnetic NMR Analysis of Substituted Biscyclooctatetraene Lanthanide Complexes

et al. 2016

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Cyclooctatetraene derivatives (COTR) with two carbocycles attached to the central ring have been used as dianionic ligands for the synthesis of double-decker complexes of the type [(COTR)2M]−. Two ligand derivatives were combined with diamagnetic Y3+ and with the five paramagnetic lanthanide ions from Tb3+ to Tm3+. The more complex substitution pattern in comparison to the parent ligand COT or the popular bis-trimethylsilyl derivative allows a sufficient number of signals to be obtained for a comprehensive paramagnetic NMR analysis. The anionic double-decker complexes gave well-resolved NMR spectra where almost all 1H and 13C NMR signals could be detected and assigned. With these data, it was possible to separate the two main contributions to the paramagnetic shift (pseudocontact and Fermi contact shifts, respectively) and to determine the magnetic anisotropy of the lanthanide ions in their ligand fields. We can easily obtain the sign and the magnitude of the anisotropy of the magnetic susceptibility, which is itself strongly related to the energy barrier for spin reversal in single-molecule magnets. Our results confirm that Bleaney factors are inadequate descriptors for magnetic anisotropy in these lanthanide complexes.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Paramagnetic NMR Analysis of Substituted Biscyclooctatetraene Lanthanide Complexes

et al. 2016

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“…11 or 12 provided that the complexes are isostructural. In this case F i and

A_{2}^{0} 〈 r^{2} 〉 \cdot G_{i}

are invariant along the lanthanide series and their values can be determined by fitting either equation, thereby allowing separation of the contact and pseudocontact shifts 33–35. However, the assumption that the complexes are isostructural along the lanthanide series does not always hold true and gradual changes in the coordination geometry can give rise to variations of the crystal field coefficient and the hyperfine coupling constant across the series.…”

Section: Paramagnetism Of the Trivalent Lanthanide Ionsmentioning

confidence: 99%

Alternatives to Gadolinium-Based Metal Chelates for Magnetic Resonance Imaging

et al. 2010

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“…Probably in the first case the effect of the gradual change of G a factors is amplified by the division by S z i , a parameter which is relatively large for Gd Ã/Er. However, such breaks could also arise if F a values [17] and/or the crystal field parameter A 2 0 r 2 [20] [21]. Based on Reuben's crystal field parameter independent method for the LIS data analysis [20], the following equation, involving the shifts of two nuclei a and b can be deduced:…”

Section: Introductionmentioning

confidence: 99%

Analysis of lanthanide induced NMR shifts using a crystal field independent method: application to complexes of tetraazamacrocyclic ligands

Ren

Zhang

Sherry

et al. 2002

Inorganica Chimica Acta

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The linear graphical analysis of the LIS NMR data available for the axially symmetric complexes [Ln(DOTA)] ( (M and m isomers), [Ln(DOTP)] 5( (pH 10.0, 7.0 and 3) and [Ln(DOTEA)] 3' using the classical crystal field dependent method and a crystal field independent method were compared. As the second method provides ratios of geometric structural terms G rather than G values, the effect of lanthanide contraction was reduced. Thus, the large breaks in plots observed for all nuclei of those systems using the classical method are still present in the plots of the second method, only in a few of the nuclei and much reduced. This shows that the large breaks at the middle of the lanthanide series present in plots of the classical method as well as the anomalies often present for those plots for the Tm and Yb ions are mostly due to changes of the crystal field coefficient A 2 0 r 2 along the lanthanide series, while both the hyperfine coupling constants and the ratios of geometric terms also change as a result of the lanthanide contraction, leading to small breaks at the middle of the lanthanide series. Analysis of the proton shifts of [Ln(DOTP)] complexes at pH 10, 7 and 3 indicates that protonation of the complexes results in a decrease on the crystal field coefficient. The dipolar shift ratios and absolute shifts obtained were also interpreted in terms of the structural models for those complexes in solution and their available Xray crystal structures. #

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Structural information from chemical shifts in lanthanide complexes

Cited by 27 publications

References 16 publications

Paramagnetic NMR Analysis of Substituted Biscyclooctatetraene Lanthanide Complexes

Paramagnetic NMR Analysis of Substituted Biscyclooctatetraene Lanthanide Complexes

Alternatives to Gadolinium-Based Metal Chelates for Magnetic Resonance Imaging

Analysis of lanthanide induced NMR shifts using a crystal field independent method: application to complexes of tetraazamacrocyclic ligands

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