Lanthanoid ions

The measurment in twophase systems is discussed by the example of dithizonate of zinc, in pseudomonophase systems - by the example of zinc and cadmium complexes with l-(2-pyridylazo)-2-naphthol, lanthanoid ion complexes with l-(2-pyridylazo)-resorcin. 

Besides the d° or d10 species, the square pyramidal complexes containing d1 and d2 ions, e.g., VO(OEP) and MoO(OEP) (-+[12] 55), and most of the complexes with lanthanoid ions (56) behave spectrally normal. 

Optical Detection of the Lanthanoid Ion Contraction by Internal Charge-Transfer Absorption of Rare Earth Bisporphyrinate Double-deckers... 

The other doubledeckers containing the metals La, Pr, Nd, Sm -Lu have rather similar spectra that have less well distinct bands in the visible region. The extinction at 573 nm is much less than in A, Peaks occur at about 540 and 670 nm. The latter absorption is typical for 3T-cation radicals (10), Indeed, the composition Ln(0EP)2 can only be accomodated with the normal trivalent state of nearly all of the lanthanoid ions if one assumes that the... 

On the contrary, a quite systematic behavior with the lanthanoid ion contraction is observed. A plot of the energy of CTI band versus the ionic radius at coordination number 8 of the Ln ions (16) indicates a linear decrease of this energy as the ionic radius increases. This is seen in Figure 3, and illustrates a bare size effect of the energy variation. The phenomenon is called "optical detection of the lanthanoid ion contraction by internal charge transfer absorption". 

Another explanation for the effect of the lanthanoid ion contraction on the energy of the NIR-CTI band may be found in the extent of doming of the porphinato ligands in the Ln(P)2 structures. A comparison of the inclination angles of the pyrrole units in and... 

At this level of approximation the AOM is at an advantage over CFT which requires two parameters in cubic symmetry. This simple treatment is Successful at the first level only in dealing with the rich spectra of lanthanoid ions in situations of mean cubic symmetry. However, as such it offers some measure of transferability not found amongst CFT parameters, and it may be possible to attach some relative chemical significance to the ea parameters for different ligands. 

However, there does not seem to be sufficient experimental data of sufficient accuracy to have made that elaborate procedure worthwhile. It has proved possible to use the diagrams published for the lanthanoid ion case with some success for treating the magnetic properties of actinoid complexes in at least some cases.49-85... 

Modification of the ligand by replacing the quinoline with a pyridine group allows the introduction of lanthanoid ions (Eu3+, Tb3+) into the cage and luminescence properties [144]. 

For the formation of acetate complexes, Table 2, the values of AH are still quite positive not only for the hard lanthanoid ions, where a markedly electrostatic bond is certainly expected, but also for Cu2+, Zn2+ and Cd2+ which are all in the border region between hard and soft acceptors. Only for the soft Pb2+, and also for H+, AH is 0. All acetate complexes so far investigated are thus entropy stabilized, i.e. oxygen behaves as a very hard donor atom also in the environment presented by the acetate ion. 

For glycolates, data are available only for lanthanoid ions, and for H+, Table 3. In this case AH is just below 0 even for the hard lanthanoid acceptors, thus slightly favouring the complex formation. The main contribution to the stability is still provided by gain of entropy, however, though also this term has a significantly lower value than for the acetate complexes. 

Regioselective 1,2-reduction of enones to the corresponding allylic alcohols is achieved with NaBH4 in the presence of lanthanoid ions, such as La +, Ce ", Sm + Eu ", Yb + and This procedure is... 

Sugiura, M., Effect of quaternary ammonium salts on carrier mediated transport of lanthanoid ions through cellulose triacetate membranes. Sep. Sci. Tech., 1993, 28 1453-1463. 

Recently, attention has been focused on lanthanoid/crown ether complexes,5 since they may be used for lanthanoid ion separation, for stabilizing unusual oxidation states, and for studying high coordination numbers, Moreover, lan-thanoid(III) ions are increasingly used as spectroscopic probes in systems of biological interest.6... 

N2, <10 ppm H20). All the complexes are microcrystalline powders with the characteristic color of the lanthanoid ions. Complexometric analyses are performed with edta (Titriplex III, Merck), using xylenol orange and urotropine. 

Comment, with reasoning, on how you expect the trend in radii for the lanthanoid ions between La and to vary. 

Worked example 24.2 Calculating the effective magnetic moment of a lanthanoid ion... 

A common interpretation of this reaction invokes the use of the cerium(lll) chloride as a Lewis acid that bonds to the carbonyl system, to make 1,2-addition favored. However, lanthanoid ions are known to preferentially bind to alcohols rather than carbonyl groups.6 Additionally, if the cerium did bind with the carbonyl, one would expect that as dilution with methanol was increased, the observed regioselectivity, presumably due to this complexation, should be reduced. However, experimental results do not support this hypothesis. Since cerium complexation with methanol would result in increased acidity of the methanolic proton, the following scheme appears to be the more likely course of the reaction. 

Comba, P. Gloe, K. Inoue, K. Krueger, T Stephan, H. Yoshizuka, K. Molecular mechanics calculations and the metal ion selective extraction of lanthanoid ions. Inorg. Chem. 1998, 37, 3310. 

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