Construction of three one-dimensional zinc(II) complexes containing pyrazine-2,3-dicarboxylic acid

Two 2D Co(II)/Mn(II) coordination polymers based on the quinoline-2,3-dicarboxylate ligand: synthesis, crystal structure, and fluorescence properties

A pair of two-dimensional (2D) isostructural coordination polymers (CPs), {[Co(2,3-qldc)(H2O)]} n (1) and {[Mn(2,3-qldc)(H2O)]} n (2), where 2,3-H2qldc = quinoline-2,3-dicarboxylic acid, were hydrothermally synthesized and characterized through IR spectroscopy, elemental and thermal analysis, power X-ray diffraction, and single-crystal X-ray diffraction. The results have revealed that the fully deprotonated 2,3-H2qldc ligand connects the Co(II)/Mn(II) atoms with a μ 3-bridge to form a square-wave 2D network, which is further extended into 3D stacks through O–H···O, C–H···O hydrogen bonds and π···π stacking interactions. Topologically, 1 or 2 can be simplified as a 4-connected sql type with a Schläfli symbol {44·62} and a Shubnikov tetragonal plane net, or as a 3-connected fes type with a Schläfli symbol {4·82} and a Shubnikov plane net. The thermal stability and the solid state fluorescence properties of 1 and 2 were investigated.

Crystal and molecular structure of [Ni{2-H2NC(=O)C5H4N}2(H2O)2][Ni{2,6-(O2C)2C5H3N}2]·4.67H2O; DFT studies on hydrogen bonding energies in the crystal

[Ni{2-H₂NC(=O)C₅H₄N}₂(H₂O)₂][Ni{2,6-(O₂C)₂C₅H₃N}₂]·4.67H₂O, a new complex salt containing a bis(2,6-dicarboxypyridine)nickel(II) anion and a bis(2-amidopyridine)diaquanickel(II) cation, was synthesized and characterized. The crystal is stabilized by an extensive network of hydrogen bonds. Alternate layers of anions and cations/water molecules parallel to (010) can be distinguished. Computational studies of the network packing of the title compound by high-level DFT-D/B3LYP calculations indicate stabilization of the networks with conventional and non-conventional intermolecular O-H...O, N-H...O and C-H...O hydrogen bonds along with π-stacking contacts. Due to the presence of water molecules and the importance of forming hydrogen bonds with the involvement of water clusters to the stability of the crystal packing, the importance and role of these water clusters, and the quantitative stability resulting from the formation of hydrogen bonds and possibly other noncovalent bonds such as π-stacking are examined. The binding energies obtained by DFT-D calculations for these contacts indicate that hydrogen bonds, especially O-H...O and N-H...O, control the construction of the crystalline packing. Additionally, the results of Bader's theory of AIM for these interactions agree reasonably well with the calculated energies.

Two Different Barium(II) 2D Coordination Polymers Constructed with Pyrazine-2,3-Dicarboxylate: Synthesis, Crystal Structures, and Thermal Decomposition to Barium(II) Carbonate Nanoparticles

Two novel barium(ii) 2D coordination polymers, {[Ba(µ-H2O)(H2O)2(µ-pyzdc)]}n (1) and {[Ba(H2O)2(µ-Hpyzdc)(Hpyzdc)]⋅2H2O}n (2) (pyzdcH2 = pyrazine-2,3-dicarboxylic acid), were prepared by reaction of barium(ii) chloride dihydrate and pyrazine-2,3-dicarboxylic acid under similar experimental conditions (slightly different pH values) and characterised by elemental analysis, IR spectroscopy, and thermogravimetric analysis/differential thermal analysis methods. Their crystal structures were determined by single-crystal X-ray structure analysis and it was revealed that the barium(ii) ion has a distorted bicapped square antiprismatic coordination geometry in 1 and a distorted tricapped trigonal prismatic geometry in 2, composed of water molecules, carboxylate O, and pyrazine N atoms in both cases. The polymers 1 and 2 have different connectivity, as the pyrazine-2,3-dicarboxylate ion acts as multidentate bridging ligand in both 1 and 2, but also as an N,O′-bidentate terminal ligand in 2. There are terminal coordinated water molecules in both 1 and 2, but bridging water molecules are present only in 1 and water molecules of crystallisation only in 2. BaCO3 nanoparticles were formed by thermal decomposition of 1 in the presence of polyethylene glycol, and their structure and morphology were studied by powder X-ray diffraction and scanning electron microscopy. According to the powder X-ray diffraction pattern, BaCO3 was formed with an orthorhombic witherite structure.

Structures of CoIIand ZnIIcomplexes of the proton-transfer compound derived from pyrazine-2,3-dicarboxylic acid and piperazine

The reaction of the proton-transfer compound piperazine-1,4-diium pyrazine-2,3-dicarboxylate 4.5-hydrate, C4H12N22+·C6H2N2O42−·4.5H2O or (pipzH2)(pyzdc)·4.5H2O (pyzdcH2is pyrazine-2,3-dicarboxylic acid and pipz is piperazine), (I), with Zn(NO3)2·6H2O and CoCl2·6H2O results in the formation of bis(piperazine-1,4-diium) bis(μ-pyrazine-2,3-dicarboxylato)-κ3N1,O2:O3;κ3O3:N1,O2-bis[aqua(pyrazine-2,3-dicarboxylato-κ2N1,O2)zinc(II)] decahydrate, (C4H12N2)2[Zn2(C6H2N2O4)4(H2O)2]·10H2O or (pipzH2)2[Zn(pyzdc)2(H2O)]2·10H2O, (II), andcatena-poly[piperazine-1,4-diium [cobalt(II)-bis(μ-pyrazine-2,3-dicarboxylato)-κ3N1,O2:O3;κ3O3:N1,O2] hexahydrate], {(C4H12N2)[Co(C6H2N2O4)2]·6H2O}nor {(pipzH2)[Co(pyzdc)2]·6H2O}n, (III), respectively. In (I), pyzdcH2is doubly deprotonated on reaction with piperazine as a base. Compound (II) crystallizes as a dimer, whereas compound (III) exists as a one-dimensional coordination polymer. In (II), two pyzdc2−groups chelate to each of the two ZnIIatoms through a ring N atom and an O atom of the 2-carboxylate group. In one ligand, the adjacent 3-carboxylate group bridges to a neighbouring metal atom. A water molecule ligates in the sixth coordination site. The structure of (II) can be described as a commensurate superlattice due to an ordering in the hydrogen-bonded network. In (III), no water is coordinated to the metal atom and the coordination sphere is comprised of twoN,O-chelates plus two bridging O atoms. A large number of hydrogen bonds are observed in all three compounds. These interactions, as well as π–π and C=O...π stacking interactions, play important structural roles.

Poly[[(N,N-dimethyl-formamide-κO)(μ(3)-pyrazine-2,3-dicarboxyl-ato-κN,O:O:O)copper(II)] monohydrate]

In the title compound, {[Cu(C(6)H(2)N(2)O(4))(C(3)H(7)NO)]·H(2)O}(n), the Cu(II) atom is coordinated by an N,O-bidentate pyrazine-2,3-dicarboxyl-ate (pzdc) dianion, two O atoms from two other pzdc anions and one O atom from the dimethlyformamide ligand, forming a distorted square-pyramidal CuNO(4) geometry. The polymeric character of the structure is established by the formation of layers parallel to (100) via bridging pzdc ligands. O-H⋯O hydrogen bonding between water mol-ecules and uncoordinated carboxyl-ate O atoms leads to additional stabilization of the structure.