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Slow Magnetic Relaxation and Luminescent Properties of Mononuclear Lanthanide-Substituted Keggin-Type Polyoxotungstates with Compartmental Organic Ligands. | LitMetric

The reaction of mid to late lanthanide ions with the ,'-dimethyl-,'-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylene-diamine organic ligand and monolacunary Keggin type [α-SiWO] anion affords a series of isostructural compounds, namely, K[Ln(α-SiWO)(CHBrNO)]·14HO (-Ln, Ln = Sm to Lu). The molecular structure of these sandwich-type complexes is formed by the Ln ion in a biaugmented trigonal prismatic geometry, which occupies the external O site of the organic ligand and the vacant site of the lacunary polyoxometalate (POM) unit. The empty NO coordination site of the organic ligand allows its unprecedented folding, which displays a relative perpendicular arrangement of aromatic groups. Weak Br···Br and π-π interactions established between adjacent molecular units govern the crystal packing, which results in the formation of assemblies containing six hybrid species assembled in a chairlike conformation. -Gd and -Yb display slow relaxation of the magnetization after the application of an external magnetic field with maxima in the out-of-phase magnetic susceptibility plots below ∼5-6 K, which is ascribed to the presence of various relaxation mechanisms. Moreover, photoluminescent emission is sensitized for -Sm and -Eu in the visible region and -Er and -Yb in the NIR. In contrast, the quenching of metal-centered luminescence in the -Tb derivative has been attributed to the out-of-pocket coordination mode of the lanthanide center within the POM fragment. It is demonstrated that the -Yb dual magneto-luminescent material represents the first lanthanide-containing POM reported to date with simultaneous slow magnetic relaxation and NIR emission. Solution stability of the hybrid molecular species in water is also confirmed by ESI-mass spectrometry experiments carried out for -Tb and -Tm.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8826278PMC
http://dx.doi.org/10.1021/acs.inorgchem.1c03214DOI Listing

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