Lanthanide metal-organic frameworks containing ferromagnetically coupled metal-carboxylate chains showing slow magnetic relaxation behavior

Abstract

Lanthanide metal-organic frameworks (Ln-MOFs) with slow magnetic relaxation behavior are of great interest to scientists due to their rich and peculiar physical phenomena and spin-related applications. In this contribution, the syntheses, characterizations and magnetic properties of two new Ln-MOFs: {[Ln2(btpdc)3·DMF·2H2O]·2DMF·4H2O}n (Ln = Dy (1), Gd (2), H2btpdc = benzo[b]thiophene-2,6-dicarboxylic acid) are reported. Single crystal X-ray diffraction experiments show the two complexes are isostructural with three dimensional (3D) porous framework structure constructed by metal-carboxylate chains separated by long organic linkers. Direct-current (dc) magnetic susceptibilities recorded under 1000 Oe reveal the overall exchange couplings in both the two MOFs are ferromagnetic. Interestingly, the ferromagnetic coupled metal-carboxylate chains in 1 are sufficiently isolated by the long organic linkers that makes 1 exhibit slow magnetic relaxation behavior and Ising-like behavior which was rarely reported for lanthanide-carboxylate complexes.