Combination of lacunary polyoxometalates (POMs) with lanthanide ions constitutes a powerful tool to design architectures with applications in i) catalysis, due to their Lewis-acid nature; ii) magnetism: some species can act as single-molecule magnets (SMM) or even, single-ion magnets (SIM) with potential applications in quantum computing or data storage and; iii) luminescence, because POMs can act as antenna ligands, sensitizing the emission of lanthanide centers. The use of compartmental organic ligands bearing aromatic groups has proved to be effective to prepare lanthanide-based or heterometallic 3d/4f dual magneto-luminescent materials. However, the effect of the simultaneous use of POMs, compartmental organic ligands and 4f metals has not been studied yet. Herein, we report the reaction between mid-to-late lanthanide salts, the N,N’-dimethyl-N,N’-bis(2-hydroxy-3-formyl-5-bromobenzyl)ethylenediamine (H2L) ligand and the monolacunary α-Keggin polyoxometalate [α-SiW11O39]8−, which leads to the namely isostructural compounds K5[α-SiW11O39LnIII(C20H22N2Br2O4)]●14 H2O (1-Ln, LnIII=Sm to Lu). All derivatives have been chemically and structurally characterized, and their magnetic and photophysical properties measured. Among these species, 1-Gd and 1-Yb derivatives exhibited attractive field-induced SMM properties, showing slow relaxation of the magnetization after the application of 3500 Oe magnetic field. Additionally, 1-Sm, 1-Eu displayed metal-centered photoluminescence in the visible region, whereas 1-Er and 1-Yb emitted in the NIR region.

Luminescent and SMM behavior of lanthanide-substituted Keggin-type polyoxotungstates with compartmental organic ligands

ACS Fall 2021

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