Lanthanide Containing Complexes

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. 

The magnetic relaxation phenomena in lanthanide-containing complexes cover a wide range of magnetic materials, among which the SMMs and single-chain magnets (SCMs) are the two most important families of molecular materials. 

Mukaiyama aldol reactions, whereby trimethylsilyl enol ethers react with aldehydes in aqueous solution to form -ketoalcohols, have been promoted by new chiral lanthanide-containing complexes and a chiral Fe(II)-bipyridine complex with 0 outstanding diastereo- and enantio-selectivities. Factors controlling the diastereoselec-tivity of Lewis-acid-catalysed Mukaiyama reactions have been studied using DFT to reveal the transition-state influences of substituents on the enol carbon, the a-carbon of the silyl ether, and the aldehyde. The relative steric effects of the Lewis acid and 0 trimethyl silyl groups and the influence of E/Z isomerism on the aldol transition state were explored. Catalytic asymmetric Mukaiyama aldol reaction of difluoroenoxysilanes with /-unsaturated a-ketoesters has been reported for the first time and studied extensively. ... 

To date, the only organometallic lanthanide porphyrin complexes to be reported contain yttrium and lutetium, and they will be considered in the section on scandium. Representative structural types of porphyrin complexes containing groups 3 and 4 metals are shown in Fig. 3 and selected data for all the structurally characterized complexes are given in Table 11. 

The photochemical process will in general not occur in non-molecular solids due to the restriction in the nuclear coordinates. However, the nonradiative return to the ground state does, using MMCT states as an intermediary [35]. This can be nicely illustrated on a molecular solid, viz. the lanthanide-decatung-states which contain complex ions [Ln(III)Wio036] [40, 121]. 

Synthesis of Heteroleptic Lanthanide(lll) Complexes Containing Porphyrin-Based Ligands... 

Another lanthanide carboxylate complex that also contains nonacoordinated lanthanide ion in a monocapped square antiprismatic arrangement of nine oxygens is the erbium oxalate trihydrate with the composition Er(OOCCOO) (HOOCCOO) (OH2)3. This complex crystaUizes (767) in space group P4/ with 0 = 8.664, c =6.4209 A and Z=2, when the precipitate of erbium oxalate, ob-... 

Casellato, U. Tamburini, S. Tomasin, P. Vigato, P. A. Botta, M. Lanthanide(III) complexes with a podand Schiff base containing an N403 coordination site. Inorg. Chim. Acta 1996, 247,143-145. 

The detection of aromatic carboxylates via the formation of ternary complexes using lanthanide ion complexes of functionalised diaza-crown ethers 30 and 31 has been demonstrated [134]. Like the previous examples, these complexes contained vacant coordination sites but the use of carboxylic acid arms resulted in overall cationic 2+ or 1+ complexes. Furthermore, the formation of luminescent ternary complexes was possible with both Tb(III) and Eu(III). A number of antennae were tested including picolinate, phthalate benzoate and dibenzoylmethide. The formations of these ternary complexes were studied by both luminescence and mass spectroscopy. In the case of Eu-30 and Tb-30, the 1 1 ternary complexes were identified. When the Tb(III) and Eu(III) complexes of 30 were titrated with picolinic acid, luminescent enhancements of 250- and 170-fold, respectively, were recorded. The higher values obtained for Tb(III) was explained because there was a better match between the triplet energy of the antenna and a charge transfer deactivation pathway compared to the Eu(III) complex. 

The lanthanide phthalocyanine complexes, obtained by conventional methods starting from metal salts at 170-290°C and phthalonitrile (Example 26), contain one or two macrocycles for each metal atom [5,6,8,63,82,84-98]. Thus, according to Refs. 6,63, and 85, the complexes having compositions LnPc2H, XLnPc (X- is halide anion), and Ln2Pc3 (a super-complex ) were prepared from phthalonitrile as a precursor the ratio of the reaction products depends on the synthesis conditions and the metal nature. The ionic structure Nd(Pc)+Nd(Pc)2 was suggested [85] and refuted [63] for the neodymium super-complex Nd2Pc3 the covalent character of the donor-acceptor bonds in this compound and other lanthanide triple-decker phthalocyanines was proved by the study of dissociation conditions of these compounds [63]. 

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