Complexes lanthanide-like behaviour

The structures and dynamic magnetic behaviours of 31-Dy4 and 31-Tb4 have been presented in Figure 3.22. Four lanthanide ions are aggregated in the grid-like metal core by a central p4-S and eight peripheral i2-S atoms from ethanethiol ligands [38]. The individual lanthanide centres occupy distorted six-coordinate [LnNS5] octahedral coordination environments. Ac susceptibilities measurements reveal pronounced temperature dependence with a series of maxima below 28 K, typical for SMM behaviour, in complex 31-Dy4. Furthermore, an... 

Lanthanides properties and general references. For a systematic treatment and general references of the physical and chemical properties of the rare earths and their compounds and alloys mention can be made to a periodical publication in which several contributions to these subjects are being collected. See for instance Gschneidner and Eyring (1978) and Gschneidner etal. (2005). We would also like to quote a sentence, included in the prefaces of all these books, which hints at the complexity and richness of the rare earth behaviour and the ever-increasing interest in their properties and applications. The mentioned sentence is as follows ... 

Where the lanthanide ionic radius and the macrocyclic cavity are incompatible, though in hydrous conditions the crown ether is likely to be displaced by water ligands, the crown may still be present in the structure of the crystal as a hydrogen-bonded adduct. This behaviour is seen in [Gd(N03)3(H20)3]-(18-crown-6).445 This type of compound is quite well known in the case of s block metals also, e.g. [Mg(H20)6]Cl2 (12-crown-4)454 and, a more subtle case, [Ca(nitrobenzoate)2(benzo-15-crown-5)]-3H20(benzo-15-crown-5)455 in which an apparent 2 1 complex has only half its crown ligand coordinated to Ca2+. 

In many respect the fifteen acinides [Ac(Z = 89) to Fm(Z = 103)] with their 5/ configurations, are similar to their lanthanide counterpart. Thus the chemical properties like the extraction behaviour, complex formation and the spectroscopic properties often show close parallelism with those of the lanthanides. The Lande parameter, f5y, is some two to two and half times larger in the 5/series than in the corresponding 4/ series. As a result of this, the deviation from the Russell-Sauders coupling in the 5/ series is much more pronounced than in the 4/series. However, it has been shown earlier by Sinha 58) that the hydration entropies, enthalpies and the crystal parameters for the fluorides of the tri- and tetravalent actinides (Fig. 55, 56) also follow a linear L-dependence and give rise to the inclined W plots like those for the lanthanides. 

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