Lanthanide metal–organic frameworks based on the 4,4′-oxybisbenzoic acid ligand: synthesis, structures and physical properties

Abstract

A series of lanthanide microporous coordination polymers, namely, {[Ln₄(OBA)₆(DMF)(H₂O)]·2DMF·3H₂O}_n [Ln = Nd(1), Sm(2), Eu(3), Gd(4)]; {[Ln₄(OBA)₆(H₂O)₂]·3DMF·2H₂O}_n [Ln = Tb(5), Dy(6)]; {[Ln₄(OBA)₆(DMF)(H₂O)₂]·2DMF·4H₂O}_n [Ln = Tb(7), Dy(8)] (H₂OBA = 4,4′-oxybisbenzoic acid, DMF = N,N′-dimethylformamide), have been successfully prepared via solvothermal methods and characterized by FT-IR, photoluminescence spectra, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. All of the lanthanide coordination polymers showed three dimensional (3D) metal–organic frameworks. The structural variations in compounds 1–8 may be caused by lanthanide contraction and different coordination modes of V-shaped H₂OBA ligands. The luminescence properties of compounds 3, 5 and 7 have been studied in the solid state at room temperature, and all of them displayed metal-based luminescence. Moreover, compounds 4, 6 and 8 exhibited antiferromagnetic coupling within the carboxyl oxygen bridged rare-earth chains.