Synthesis, Ab Initio X-ray Powder Diffraction Crystal Structure, and Magnetic Properties of Mn3(OH)2(C6H2O4S)2 Metal-Organic Framework

A new hydroxythiophenedicarboxylate metal-organic framework based on Mn-II cations has been obtained by an aqueous two-step procedure including hydrothermal treatment. The structure of Mn-3(OH)(2)(C6H2O4S)(2) has been determined ab initio from synchrotron X-ray powder diffraction data and consists of infinite inorganic ribbons which are interlinked by 2,5-thiophenedicarboxylate (tdc) molecules (monoclinic, space group P2(1)/c, a = 3.4473(1) angstrom, b = 19.1287(1) angstrom, c = 11.0069(1) angstrom, beta = 97.48(1)degrees, V = 719.65(1) angstrom(3), and Z = 2). Each ribbon is built of three vertex-sharing chains of edge-sharing MnO6 octahedrons. These ribbons are bridged together by the carboxylate functions of the tdc molecule to form a pseudo-2D inorganic subnetwork, while this molecule develops in the third dimension to pillar these pseudo-2D layers. An unprecedented hexadentate symmetric bridging mode is adopted by tdc which bridges two chains of a ribbon on one side and two ribbons of a pseudo-2D inorganic subnetwork on the other side. Magnetic measurements suggest that the titled compound is antiferromagnetic below T-N = 17.7 K. Heat capacity measurements confirm the existence of a magnetic phase transition toward a 3D long-range ordered state. These C-P(T) data have also been used for the calculation of the thermal variations of both the adiabatic temperature change Delta T-ad and magnetic entropy change Delta S-m of the material, namely its magnetocaloric effect.