Syntheses, structures, magnetic and photoluminescence properties of metal–organic frameworks based on aromatic polycarboxylate acids

Abstract

Six new coordination compounds, namely [Co(H₂bptc)]_n (1), [Mn(H₂bptc)]_n (2), [Cd₂(bptc)(phen)₂(H₂O)₂]_n (3), [Eu₂(cpa)₃(DMF)₂]_n (4), [Nd₂(cpa)₃(DMF)₂]_n (5) and [Pr₂(cpa)₃(DMF)₂]_n (6) (bptc⁴⁻ = biphenyl-2,2′,4,4′-tetracarboxylate anion, phen=1,10-phenanthroline, cpa²⁻ = 4-chloroisophthalic acid anion) were synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra, and thermogravimetric analysis. Co and Mn compounds are isostructural, and possess a three-dimensional 5, 5-connected network. In Cd compound, multicarboxylate ligand H₄bptc link Cd centers to generate a two-dimensional 4, 4-c net structure with phen acting as terminal ligand. Eu, Nd, and Pr compounds have similar structures, and cpa²⁻ ligands link lanthanide cations to generate a two-dimensional sheet structure. Magnetic susceptibility measurements indicate that the Co compound has a dominating ferromagnetic coupling between Co(II) ions, and Mn compound exhibits antiferromagnetic coupling between Mn(II) ions. Furthermore, their luminescent properties are also determined in the solid state at room temperature.