High Coordination Polyhedra of Trivalent Rare Earth Ions
When they are bonded to multidentate ligands or to small bidentate ions, rare-earth ions can form complexes with high coordination numbers. The resulting coordination polyhedra usually possess a low symmetry. However, close scrutiny of the polytopes very often reveal that they arise from a slight distortion of a more symmetrical entity. This can be expected since the bonding of Ln(III) ions is essentially non-directional; the interesting point is that for Eu(III) compounds, the symmetry of this idealized polyhedron may be estimated from the emission spectra or, more precisely, from the crystal field splitting of the J-levels. To illustrate this point, we discuss here some examples of nitrato complexes in which the Eu(III) ion is 10-, 11-, and 12-coordinate.
KeywordsTrigonal Bipyramid High Coordination Crystal Field Splitting Slight Distortion High Coordination Number
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