Bimodal magneto-luminescent dysprosium (DyIII)-potassium (KI)-oxalate framework: magnetic switchability with high anisotropic barrier and solvent sensing

We report synthesis, characterization, and properties of a multifunctional oxalate framework, {KDy(C2O4)2(H2O)4}n (1) (C2O42- = oxalate dianion) composed of two absolutely different metal ions in terms of their size, charge, and electronic configuration. Dehydrated framework (1′) exhibits permanent porosity and interesting solvent (H2O, MeOH, CH3CN, and EtOH) vapor sorption characteristics based on specific interactions with unsaturated alkali metal sites on the pore surface. Compound 1 shows solvent responsive bimodal magnetic and luminescence properties related to the DyIII center. Compound 1 exhibits reversible ferromagnetic to antiferromagnetric phase transition upon dehydration and rehydration, hitherto unknown for any lanthanide based coordination polymer or metal-organic frameworks. Both the compounds 1 and 1′ exhibit slow magnetic relaxation with very high anisotropic barrier (417 ± 9 K for 1 and 418 ± 7 K for 1′) which has been ascribed to the single ion magnetic anisotropy of the DyIII centers. Nevertheless, compound 1 shows a metal based luminescence property in the visible region and H2O molecules exhibit the strongest quenching effect compared to other solvents MeOH, MeCN, and EtOH, evoking 1′ as a potential H2O sensor.