Crystal of lanthanides

Fra.ctiona.1 Crystallization. Fractional crystallization, used until the early part of the twentieth century, is uneconomical for processing large quantities of lanthanides. Many recrystallization steps are required to recover high purity products. Several salts and double salts have been used ... 

Previously, all these variations led to the discovery of lanthanide nitridoborates. Products were obtained as powders or single crystals, and crystal structures... 

Modelling the Magnetic Properties of Lanthanide Single-Ion Magnets The Use of the Crystal Field Model... 

Except for the factors mentioned above, such as the reactant ratio employed, variation of lanthanide and transition metal, crystallization conditions, and the presence of a secondary ligand, there are several other factors that can affect the controllable assembly of the lanthanide-transition metal-amino acid cluster compounds. 

We have summarized our research findings in a systematic study of lanthanide-transition metal-amino acid clusters. Several factors of influence that affect the assembly, such as the presence of a secondary ligand, variation of lanthanide, crystallization conditions, the ratio of metal ions to amino acids, and the choice of... 

Complexes of the lanthanides with a few cyclic amides are known. Miller and Madan have reported the complexes of 7-butyrolactam with lanthanide nitrates (60) and perchlorates (61). Complexes of lanthanide perchlorates and lighter lanthanide nitrates with BuL have a L M of 8 1. However, complexes of heavier lanthanide nitrates have a L M of only 3 1. By changing the solvent used for the crystallization of the abovementioned complexes, complexes of the formula [La(BuL)4(N03)3] and [Gd(BuL)3(N03)3] could be prepared (60). Complexes of NMBuL (61, 62) and CLM (63-66) have also been reported. 

Probably, the first series of lanthanide complexes with neutral oxygen donor ligands is that of AP with the lanthanide nitrates. In 1913, Kolb (79) reported tris-AP complexes with lighter lanthanide nitrates and tetrakis-AP complexes with heavier lanthanide nitrates. Subsequently, complexes of lanthanide nitrates with AP which have a L M of 6 1 and 3 1 have also been prepared (80-82). Bhandary et al. (83) have recently shown through an X-ray crystal and molecular structure study of Nd(AP)3(N03)3 that all the nitrates are bidentate and hence the coordination number for Nd(III) is nine in this complex. Complexes of AP with lanthanide perchlorates (81, 84), iodides (81, 85), and isothiocyanates (66, 86, 87) are known. While the perchlorates and iodides in the respective complexes remain ionic, two of the isothiocyanates are coordinated in the corresponding complexes of AP with lanthanide isothiocyanates. 

Useful structural data have been obtained from single crystal X-ray diffraction methods for a number of lanthanide complexes (15,17). In this section, the structures of various complexes with neutral oxygen donor ligands which have been studied by single crystal X-ray diffraction methods are described. For convenience, the structures are discussed in terms of coordination numbers of the lanthanide ions. 

All lanthanide ions, with the exception of gadolinium(III) and europium(II), are likely to be relaxed by Orbach-type processes at room temperature. In fact, the f" configurations n l) of lanthanides(III) give rise to several free-ion terms that upon strong spin-orbit coupling, provide several closely spaced energy levels. Table III reports the multiplicity of the ground levels, which varies from 6 to 17, and is further split by crystal field effects. 

More recently, Aspinah et al. reported the synthesis of a series of lanthanide silsesquioxanes resulting from reactions of 3 with lanthanide tris(silylamides) Ln[N(SiMc3)2]3 (Ln = Y, La, Pr, Eu, Yb). However, single crystals of these materials suitable for X-ray diffraction could not be obtained. The somewhat complicated situation is illustrated in Scheme 25. The lanthanide tris(silylamides) reacted with two-third equivalents of the trisilanol 3 in THF to give the lanthanide silsesquioxanes 85, which are dimeric in solution at 233 K. Reaction of Ln[N(SiMe3)2]3 with one equivalent of 3 in THF resulted in complete conversion of 3 to the trisilylated compound 14, as did the reaction of Ln[N(SiMe3)2]3 with two-third equivalents of 3 in toluene. 

Relatively few structural analysis of the decacoordinated lanthanide complexes have been reported. Although the lanthanides and actinides are long suspected as candidates for having decacoordination, it was not until 1965 that Lind, Lee and Hoard 211) were able to establish decacoordination for La(III) ion in monoclinic crystals of composition [La(EDTAH)] 7H2O. To date, only about ten or so decacoordinated structures are known, but many lanthanide complexes may have a coordination number of ten. 

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