Lanthanide elements are hard acids in the classification of Pearson
[10] and, therefore, they are highly oxophilic [11,12] with a
greater affinity for ligands that have hard donor atoms than for
those that have soft donor atoms. Recently, the syntheses of lanthano-polyoxometallates
(LnPOMs) has received strong interest
and the incorporation of lanthanide ions (Ln3+) in polyoxometallatesis
has become a focus in supramolecular chemistry because
of their attractive physical properties, such as magnetic [13] and
optical properties [14] which result from the synergy between
the properties of the lanthanide ions and the POM clusters.