Pseudo-lanthanides

Mizukami, S. Houjou, H. Kanesato, M. Hiratani, K. Adjustment of twist angles in pseudo-helical lanthanide complexes by the size of metal ions. Chem. Eur. J. 2003, 9, 1521-1528. 

Figure 7.40 Structure of the spherical lanthanide p-sulfonatocalix[4]arene assembly (a) partial space filling view along the pseudo-fivefold axis. Pyridine N oxide and one calixarene are shown in stick mode. S03 groups line the surface of the sphere, aryl rings define the hydrophobic shell and the polar core comprises 30 water molecules and two Na+ ions, (b) cut away view showing an [Na(H20)6] 2 cluster within the core. (Reprinted with permission from AAAS from [52]).

Separation of contact and pseudo-contact contributions in paramagnetic lanthanide complexes 372 (L4 = tris 2-[A -methylcarbamoyl-(6-W,A -diethylcarbamoyl)pyridi-ne-2)ethyl]amine ) 390... 

S 3 paramagnetic hyperfine chemical shift in ppm for a nucleus i in a complex of a lanthanide j paramagnetic contact shift in ppm for a nucleus i in a complex of a lanthanide j <5 ° paramagnetic pseudo-contact shift in ppm for a... 

Pseudo-contact shifts and through-space interactions in paramagnetic lanthanide complexes... 

Since this dipolar interaction remains in isotropic media as similarly found for the contact shift (see sect. 2.1), it is often termed as the pseudo-contact shift. For the general case of a complex possessing an anisotropic magnetic susceptibility tensor, Kemple et al. (1988) show that the pseudo-contact shift spherical coordinates of the resonating nucleus in an arbitrary axes system with the lanthanide metal ion i (III) located at the origin (fig. 1)... 

Separation of contact and pseudo-contact contributions in paramagnetic lanthanide... 

Plots of S /(Sz)j vs Cj/(Sz)j (eq. (48)) and S /Cj vs (Sz)j/Cj (eq. (49)) using crystal-field dependent techniques show systematic abrupt breaks near the middle of the lanthanide series (between R = Eu and R = Tb) which imply a concomitant change of the contact Fi and pseudo-contact BqG terms (table 10, fig. 25). Since G is essentially invariant, an abrupt variation of the crystal-field parameter Bq is required to rationalize the NMR data. 

Axial symmetry according to Bleaney s approach is maintained in polymetallic lanthanide complexes when the metals lie on the molecular threefold or fourfold axes. For n magnetically non-coupled lanthanide ions packed along the symmetry axis, contact and pseudo-contact contributions can be considered as additive and the original model-free equation (eq. (47)) is transformed into eq. (61) in which the sum runs over the n paramagnetic centres, each being located at the origin of its own reference frame associated with a specific set of axial coordinates O 1 and r" (the z axis corresponds to the molecular symmetry axis, fig. 54),... 

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