Role of the Templating Heteroatom on Both Structural and Magnetic Properties of POM-Based SIM Lanthanoid Complexes

International audienceThe plasticity of the coordination chemistry of Lanthanoid ions (LnIII) has allow the design of novel coordination compounds with slow relaxation of the magnetization since the first Single Ion Magnet (SIMs) was reported by Ishikawa, who used the phthalocyaninate ligand to make a “sandwich type” complex. The coordination chemistry has allowed the possibility to design different types of molecular complexes with SIMs behaviour based on organic ligands. There is also SIMs based on inorganic ligands, using different types of lacunary polyoxometalates (LPOM) like, [XW11O39]n−. The combination of both types of ligands can produce hybrid inorganic-organic LnIII complexes with SIM behaviour. This is an attractive approach since these hybrid materials could benefit from the combination of the ease of functionalization of the organic ligands with the robustness of the inorganic moieties. There are reports that a hybrid mononuclear DyIII complex could improve the relaxation dynamics when it is compared to the inorganic analogues. Thus, in this review we present a study and comparison on the improvement that inorganic and organic ligands can cause to the geometry of the metal centres of fully inorganic and hybrid (mononuclear and dinuclear) lanthanoid complexes (for DyIII, ErIII and YbIII). Moreover, we will discuss which of these changes can modify the magnetic properties of the Lanthanoid Complexes

The origin of the electronic transitions of mixed valence polyoxovanadoborates [V12B18O60]: from an experimental to a theoretical understanding

International audienceMixed-valence polyoxovanadates (POVs) constitute a family of polyoxometalates whose electronic properties are still unclear. Polyoxovanadoborates (POVBs), a subfamily of POVs, show different electronic and magnetic properties compared to those of POVs. Upon the interpretation of the electronic spectra of these compounds, only three bands in the 350-800 nm range were reported in the literature. This is the first theoretical study of the electronic spectra of the [V12B18O60] family, and we showed that these three bands are the contributions of different excitations, i.e., LMCT + IVCT, d-d + IVCT and d-d + IVCT. We showed experimentally that in the NIR region, up to 1800 nm, IVCT transitions appear, whose intensity is dependent on the mixed-valence ratio. We also showed that the condensation of borate groups resulted in the loss of the differentiation of the vanadyl stretching vibration that depends on the oxidation state, which is as expected for other types of polyoxovanadates. This feature was proposed as a probe to observe the delocalized to localized phase transition in POVs