Trivalent lanthanide ions, magnetic

In principle, paramagnetic ions also may be used to induce hyperfine shifts in nucleic acids to aid detection of binding sites. Ions with high relative magnetic anisotropy and short unpaired electron relaxation times (i.e., Co Fe and trivalent lanthanide ions except for Gd ) are candidates for such studies. Indeed, Tb and Eu ions have been used as fluorescent probes of nucleic acid structures it is expected that NMR studies also would be informative. " ... 

Table 2.1 Electronic and magnetic properties of the trivalent lanthanide ions Ln +...

The situation is quite different in the case of lanthanidomesogens, because the trivalent lanthanide ions (especially Tb, Dy " ", Ho " ", Er, Tm ) have a very large magnetic anisotropy in comparison with other paramagnetic... 

TABLE 1 Quantum numbers and total f-electron magnetic moments of the trivalent lanthanide ions, is the magnetic moment calculated from Eq. (5). is the measured magnetic moment. All magnetic moments are expressed in Bohr magnetons... 

Various lanthanide complexes of hen egg-white lysozyme have been used to test the validity of the assumption of the magnetic susceptibility tensor of the metals being axially symmetric in the use of trivalent lanthanide ions as probes in n.m.r. studies of macromolecules. For Gd +-lysozyme, the broadening data place the metal ions in close proximity to the reported A -ray position. Contrary to current assumptions, the shifts induced by Nd + and Ce + exhibit considerable non-axial character. On the basis of a statistical hypothesis test, the axially symmetric model was rejected with > 97 % confidence. 

Principal magnetic dipole transitions in the absorption spectra of the trivalent lanthanide ions ... 

Values of the quantity P > 0.015 x 10" where Pmd= P n have been calculated for all of the trivalent lanthanide ions based on eigenvectors derived from energy level schemes for R (aquo) (Carnall et al., 1968a). The principal magnetic dipole transitions in the absorption spectra of the 3+ lanthanides are identified in table 24.3. 

The effective magnetic moments of all the phases indicate trivalent states for the lanthanide ions. 

Lanthanide(III) complexes demand special attention in view of the specific spectra-structure relationship for biological applications, chiral catalysis, molecular magnetism and luminescence. One unique chiral stereochemistry is realized by the combination of labile Ln complexes and weak Na+-fluorocarbon interactionwhich show intense CD (circular dichroism) with variation of Ln(III) and/or M(I) ions to chiroptical spectra-structure relations and an important role in configurational chirality for chemical sensors, NMR shift reagents or chiral catalysis. Trivalent lanthanides are also found to be incorporated into heterobimetallic complexes showing intramolecular energy transfer processes. 

Several monoxides with metallic properties (LaO, CeO, PrO, NdO, and SmO) have subsequently been synthesized by subjecting stoichiometric mixtures of metallic R and R2O3 to high pressures [56]. These oxides have metallic conductivity and can be described as (R (0 )(e ). The trivalent nature of the lanthanide ions in these oxides was confirmed by the Sm X-ray absorption edge in SmO and by the magnetic susceptibilities of PrO (Pr, 41 ), NdO (Nd, 4f ), and SmO (nearly Sm ", 4 ) [57]. The oxides are stable under high pressure because the volume decrease that accompanies the reaction... 

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