Synthesis, Structure and Magnetic Phase Transitions of the Manganese Succinate Hybrid Framework, Mn(C4H4O4)

An anhydrous manganese succinate, Mn(C4H4O4), has been synthesised hydrothermally and studied by single-crystal X-ray diffraction. It adopts a succinate pillared structure in which layers of corner-sharing MnO6 octahedra alternate with sheets that contain chains of edge-sharing octahedra. This unique 3D framework structure contains highly distorted MnO6 octahedra, which are made possible by the lack of ligand field stabilisation energy for the high-spin Mn2+ ion. Attempts to dope the structure with other divalent transition-metal ions were accordingly unsuccessful. Magnetic susceptibility and heat capacity measurements indicate that Mn(C4H4O4) undergoes antiferromagnetic ordering below 12 K, with a second antiferromagnetic transition at approximately 6 K. These two antiferromagnetic phases undergo further transitions in applied fields, underlining the subtle magnetic behaviour that is possible in inorganic organic frameworks of this structural complexity.