Lanthanide-containing Systems

Reaction of the segmented bidentate-tridentate ligand (59) with zinc(II) and lanthanum(III) or europium(III) ions in acetonitrile yielded novel heteronuclear species of type [LnZniLigJ. In part, the inherent selectivity associated with this procedure reflects the lanthanide ion s low affinity for the tridentate (six-co-ordinate) 

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We have already discussed the difficulties inherent in preparing heterometallic lanthanide containing systems under thermodynamic control. However, such robust systems are essential if we are to understand the properties of lanthanides completely. A range of approaches have been developed that can be used to ensure that single species are formed, and we will now discuss these in turn. 

This review focuses on the use and limitations of the model-free methods in axial paramagnetic supramolecular mono- and polymetallic lanthanide-containing complexes. A comprehensive survey of the systems with three- and fourfold symmetry for which these techniques have been applied is proposed together with a detailed discussion of the limitations of Bleaney s approach for the modeling of paramagnetic anisotropies and the detection of structural changes along the lanthanide series. 

This volume of the Handbook illustrates the rich variety of topics covered by rare earth science. Three chapters are devoted to the description of solid state compounds skutteru-dites (Chapter 211), rare earth-antimony systems (Chapter 212), and rare earth-manganese perovskites (Chapter 214). Two other reviews deal with solid state properties one contribution includes information on existing thermodynamic data of lanthanide trihalides (Chapter 213) while the other one describes optical properties of rare earth compounds under pressure (Chapter 217). Finally, two chapters focus on solution chemistry. The state of the art in unraveling solution structure of lanthanide-containing coordination compounds by paramagnetic nuclear magnetic resonance is outlined in Chapter 215. The potential of time-resolved, laser-induced emission spectroscopy for the analysis of lanthanide and actinide solutions is presented and critically discussed in Chapter 216. 

Dendrimer-type ligand (32) serves as a lanthanide container to exhibit on-off switchable luminescence upon lanthanide complexation in response to external anions [56]. Because of the presence of two classes of coordination sites for the lanthanide cations at the inner and outer spheres, the dendrimer 32 exhibits two different binding modes to afford on-off lanthanide luminescence, in which outer complexation at the tetradentate tripod site offers the on luminescence state upon quinoline excitation whereas, inner complexation at the multidentate core site corresponds to the off luminescence state. Upon complexation of 32 with Yb(CF3 SO3 )3, the quite weak NIR luminescence from the Yb(III) center suggests that the Yb(III) ion is most probably located at the inner coordination sites and apart from the excited quinoline moieties. Nevertheless, addition of SCN anion to the 32-Yb(CF3803)3 system induced remarkable spectral changes around the quinoline absorption band and about ninefold enhancement in luminescence intensity at around 980 nm. As the intense Yb luminescence appeared upon quinoline excitation, the employed SCN anion promoted the tripod-Yb +... 

The assumption about the bimetallic bridge structure of lanthanide catalytic systems was made in many works [66-69]. Nevertheless, the possibility must not be ruled out that active centres contain both types of bonds (tt-allyl and a-bridge). It is important that these bonds may differ dramatically in reactivities. In order to answer the question concerning the possible coexistence of two types of bonds, the polymerisation of butadiene on catalytic systems NdCl3 3L-AlR3, where R is /-C4H9 Ln is Nd or Tb L is TBP, prepared in the presence of a small amount of butadiene and piperylene [71, 72] was investigated. Table 3.3. 

Recent kinetic studies of metal ion exchanges include those of europium(iii) with its cydta complex and of various lanthanides(iii) with their respective dtpa complexes. Kinetic studies of metal ion replacement include reactions of nta, edda, heedta, egta, cydta, and dtpa complexes of zinc(ii) with copper(ii), of edta nedta, cydta, and dtpa complexes of lead(ii) with cobalt(ii), of the edta complex of nickel(ii) with indium(iii), and of ttha complexes of cadmium(ii) with lanthanides(in). There are again several systems mainly concerned with 3 + and 4+ ions, for example those involving edta and dtpa complexes of lanthanides. In systems containing ions of high charge, it seems to be easier to demonstrate the existence of dinuclear intermediates of the type invoked in associative (cf. above) pathways. 

Abstract In this chapter, we discuss how luminescent lanthanides can be incorporated into complex architectures, and use the systems described to illustrate key aspects of the behaviour of lanthanide containing assemblies in the solid state and in solution. 

For heavy-element compounds like lanthanide-containing molecules correlation effects are as important as relativistic effects when an accurate description of the system is... 

The metal ion in metallophthalocyanines lies either at the center of a single phthalocyanine ligand (Pc = dianion of phthalocyanine) (Fig. 3), or between two rings in a sandwich-type complex (40). Phthalocyanine complexes of transition metals usually contain only a single Pc ring while lanthanide-containing species usually form bis(phthalocyanines), where the r-systems interact strongly with each other. 

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