Effect of terminal ligands on assembly of manganese(II) complexes with pyrazine-2,6-dicarboxylic acid

Three complexes [Mn(pzda)(H2O)2]n (1), [Mn(pzda)(bpy)]n (2) and [Mn(pzda)(phen)(H2O)2] (3) (H2pzda = pyrazine-2,6-dicarboxylic acid, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline) were synthesized by the hydro(solvo)thermal reaction and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum. Complex 1 is a 2D bilayer structure in which each Mn(II) ion is coordinated to two oxygen atoms and two nitrogen atoms from three pzda ligands and two oxygen atoms of two water molecules. Complex 2 is a 3D metal-organic framework structure. Mn(II) is seven-coordinated: four oxygen atoms and one nitrogen atom from three pzda ligands and other two nitrogen atoms from one bpy molecule, displaying a distorted pentagonal bipyramid geometry. While complex 3 is a mononuclear structure in which Mn(II) ion is seven-coordinated to one pzda, one phen, and two water molecules. The complex is connected into a 3D supramolecular network via hydrogen-bonding and π–π stacking interactions. In each of complexes 1–3, pzda ligands adopt different coordination mode.