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(C 2 O 4 ) 2 (H 2 O) 4 } n ( 1 ) (C 2 O 4 2– = 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 (H 2 O, MeOH, CH 3 CN, 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 Dy III 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 Dy III centers. Nevertheless, compound 1 shows a metal based luminescence property in the visible region and H 2 O molecules exhibit the strongest quenching effect compared to other solvents MeOH, MeCN, and EtOH, evoking 1′ as a potential H 2 O sensor.