Bimodal
Magneto-Luminescent Dysprosium (Dy<sup>III</sup>)‑Potassium
(K<sup>I</sup>)‑Oxalate Framework: Magnetic
Switchability with High Anisotropic Barrier and Solvent Sensing
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Abstract
We
report synthesis, characterization, and properties of a multifunctional
oxalate framework, {KDy(C<sub>2</sub>O<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>}<sub><i>n</i></sub> (<b>1</b>) (C<sub>2</sub>O<sub>4</sub><sup>2–</sup> = oxalate dianion)
composed of two absolutely different metal ions in terms of their
size, charge, and electronic configuration. Dehydrated framework (<b>1′</b>) exhibits permanent porosity and interesting solvent
(H<sub>2</sub>O, MeOH, CH<sub>3</sub>CN, and EtOH) vapor sorption
characteristics based on specific interactions with unsaturated alkali
metal sites on the pore surface. Compound <b>1</b> shows solvent
responsive bimodal magnetic and luminescence properties related to
the Dy<sup>III</sup> center. Compound <b>1</b> 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 <b>1</b> and <b>1′</b> exhibit slow magnetic relaxation
with very high anisotropic barrier (417 ± 9 K for <b>1</b> and 418 ± 7 K for <b>1′</b>) which has been ascribed
to the single ion magnetic anisotropy of the Dy<sup>III</sup> centers.
Nevertheless, compound <b>1</b> shows a metal based luminescence
property in the visible region and H<sub>2</sub>O molecules exhibit
the strongest quenching effect compared to other solvents MeOH, MeCN,
and EtOH, evoking <b>1′</b> as a potential H<sub>2</sub>O sensor