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

The self-assembly reaction of (+)-dibenzoyltartaric acid (D-HDBTA) with 2,2'-bipyridine (bpy) and Mn(CHCO)·4HO yielded a new coordination polymer, namely, catena-poly[[[diaqua(2,2'-bipyridine-κN,N')manganese(II)]-μ-2,3-bis(benzoyloxy)butanedioato-κO:O] dihydrate], {[Mn(CHO)(CHN)(HO)]·2HO} or {[Mn(DBTA)(bpy)(HO)]·2HO}, (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 P222. In the complex, the Mn cation displays a distorted octahedral {MnON} geometry, formed from two carboxylate O atoms of two DBTA 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) Å. 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 Mn model due to the long intramolecular Mn...Mn distance. The zero field splitting (ZFS) contribution in the high-spin Mn cation is almost negligible and there are weak antiferromagnetic couplings between 1D chains [zJ' = -0.062 (5) cm], corresponding to an intermolecular Mn...Mn distance of 7.860 (2) Å.