Self-assembly and structure of three new Zn(II) complexes with pyrazine-2,6-dicarboxylic acid

The reaction of Zn(OAc)2·2H2O and pyrazine-2,6-dicarboxylic acid (H2pzda) with 2,2′-bipyridine (2,2′-bpy), 1,10-phenanthroline (phen) or 1,2-bis(4-pyridyl)-ethane (bpe) gave rise to three new Zn(II) complexes: [Zn(pzda)(2,2′-bpy)(H2O)]·0.5H2O (1), {[Zn(pzda)(phen)(H2O)]·H2O}2 (2) and [Zn2(pzda)2(bpe)(H2O)4]·1.75H2O (3), respectively. For 1, it is a mononuclear structure which is assembled into 3D supramolecular architecture by strong hydrogen bonds (O-H⋯O, O-H⋯N) as well as π-π stacking interactions. In 2, there are two similar mononuclear units, which are further constructed by the hydrogen bonds and π-π stacking interactions into zipper-like supramolecular structure. However, for 3, the bpe ligand bridges two Zn(II) ions cooperated with blocking ligand pzda into binuclear unit, and then the binuclear molecules are alternatively assembled into 3D supramolecular network by hydrogen bonds between the coordinated water molecules and the carboxylate oxygen atoms. The thermal properties of complexes were also investigated.