Synthesis, crystal structure and magnetic properties of a one-dimensional Mn2+ complex constructed from (+)-dibenzoyltartaric acid and 2,2'-bipyridine.

The self-assembly reaction of (+)-dibenzoyltartaric acid (D-H2DBTA) with 2,2'-bipyridine (bpy) and Mn(CH3CO2)2·4H2O yielded a new coordination polymer, namely, catena-poly[[[diaqua(2,2'-bipyridine-κ2N,N')manganese(II)]-μ-2,3-bis(benzoyloxy)butanedioato-κ2O2:O3] dihydrate], {[Mn(C18H12O8)(C10H8N2)(H2O)2]·2H2O}n or {[Mn(DBTA)(bpy)(H2O)2]·2H2O}n, (I). Complex (I) has been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA) and single-crystal and powder X-ray diffraction. It crystallizes in the orthorhombic space group P212121. In the complex, the Mn2+ cation displays a distorted octahedral {MnO4N2} geometry, formed from two carboxylate O atoms of two DBTA2- ligands, two cis-oriented N atoms from one chelating 2,2'-bipyridine ligand and two trans-oriented O atoms from coordinated water molecules. The polymer displays a 1D chain with an Mn...Mn distance of 9.428 (1) A. Due to the presence of flexible polycarboxylate and rigid bipyridyl ligands in the molecular structure, a high thermal stability of the complex is attained. The magnetic properties of (I) were analyzed based on the mononuclear Mn2+ model due to the long intramolecular Mn...Mn distance. The zero field splitting (ZFS) contribution in the high-spin Mn2+ cation is almost negligible and there are weak antiferromagnetic couplings between 1D chains [zJ' = -0.062 (5) cm-1], corresponding to an intermolecular Mn...Mn distance of 7.860 (2) A.