One-dimensional Coordination Chains Research Articles

Zn(μ- l)Cl 2] ∞: a one-dimensional (1-D) zigzag coordination chain exhibiting unique two-dimensional (2D) hydrogen-bonding supramolecular architecture

Self-assembly of the versatile bridging ligand 2,5-bis(3-pyridyl)-1,3,4-oxadiazole ( l) with ZnCl 2 in CHCl 3–H 2O medium affords a neutral one-dimensional zigzag coordination polymer [Zn(μ- l)Cl 2] ∞ ( 1), which has been characterized by IR, elemental analyses, thermogravimetric analysis (TGA) and X-ray diffraction techniques. The crystal structure of 1 reveals that the ligand molecules bridge the tetrahedral Zn II centers (ZnN 2Cl 2) in the unprecedented transoid conformation, forming a one-dimensional zigzag coordination chain. The inter-chain C–H···Cl hydrogen bonds between the pyridine rings and the coordinated chloride anions extend these 1-D coordination frameworks to result in a novel 2-D supramolecular architecture, and there exist significant edge-to-edge π–π stacking interactions between the inter-chain neighboring pyridyl rings of the ligand, which may further stabilize this structure.

Dipyrimidine-copper(II) dinitrate complexes showing magnetic interactions.

Crystals of Cu(II)(NO(3))(2)(pm)(3) (1), and two crystalline forms of Cu(II)(NO(3))(2)(H(2)O)(2)(pm)(2), (2) and (3), showed ferromagnetic, antiferromagnetic and paramagnetic interactions at extremely low temperatures, respectively. Crystal structure analyses revealed that the complexes were catena-dinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]-(pyrimidine-N(1))copper(II), [Cu(NO(3))(2)(pm)(2)](n), catena-diaquadinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]copper(II), [Cu(NO(3))(2)(H(2)O)(2)(pm)](n), and diaquadinitratodipyrimidinecopper(II), Cu(NO(3))(2)(H(2)O)(2)(pm)(2) for (1), (2) and (3), respectively. In (1) the Cu atom is coordinated by the two nitrates and N atoms of the non-bridging pyrimidine and bridging pyrimidine to form a one-dimensional coordination polymer. The complex is a five-coordinated square pyramid and can be regarded as a pseudo-seven-coordinated complex, since other short non-bonding Cu.O contacts are observed. In the crystals of (2) the pyrimidine bridges the Cu atoms to form a one-dimensional coordination chain. On the other hand, complex (3) is not a coordination polymer. It is important to form a coordination polymer for the appearance of the magnetic interactions. Types of coordination of the bridging organic moieties should also play an important role in magnetic properties. Magnetic measurements of (1) and (2) show that they are good examples of uniform S = 1/2 ferro- and antiferromagnetic Heisenberg chains with exchange parameters 2J/kB = +1.8 and -36 K, respectively.