Pei-Chi Cheng

Roles of halide anions in the structural diversity of Zn(II) complexes containing the flexible N,N′-di(4-pyridyl)adipoamide ligand

A series of Zn(II) complexes with N,N′-di(4-pyridyl)adipoamide ligands, {[ZnX2(L)]·H2O}∞ (X = Cl, 1, Br, 2 and I, 3; L = N,N′-di(4-pyridyl)adipoamide), [Zn2X4(L)2]·2DMF (X = Cl, 4 and Br, 5) and [Zn2I4(L)2]·4DMF·C4H10O, 6, were prepared and their structures determined by X-ray crystallography. Complexes 1 and 2 form double-stranded helical chains which are supported by the N–H⋯O and O–H⋯X hydrogen bonds involving the guest water molecules and the halide anions, whereas 3 shows sinusoidal chains which are interlinked by the N–H⋯O hydrogen bonds and π–π interactions. Complexes 1–3 represent a unique example that the halide anions show significant effect on folding and unfolding of the Zn(II) double-stranded helical coordination polymers. Complexes 1–3 can be transformed to the corresponding complexes 4–6, which are dinuclear with 34-membered metallocycles. In these complexes, the chloride and bromide anions play the same role in the crystal structures, while the iodide anion is distinct.

Structure-directing roles of auxiliary polycarboxylate ligands in the formation of Zn(II) and Cd(II) coordination polymers based on a flexible N,N′-di(3-pyridyl)dodecanediamide

Reactions of the flexible N,N′-di(3-pyridyl)dodecanediamide (L) with Zn(II) and Cd(II) metal salts in the presence of different polycarboxylic acids under hydrothermal conditions afforded five new coordination polymers, [Zn(2,4-PDC)(L)(H2O)]∞ (2,4-H2PDC = 2,4-pyridinedicarboxylic acid), 1, {[Zn(1,3,5-HBTC)(L)]·2H2O}∞ (1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid), 2, {[Zn(3,4-PDC)(L)]·0.5L}∞ (3,4-H2PDC = 3,4-pyridinedicarboxylic acid), 3, {[Cd(1,2-BDC)(L)(H2O)]·0.5L}∞ (1,2-H2BDC = 1,2-benzenedicarboxylic acid), 4, and {[Cd(1,3,5-HBTC)(L)1.5]·2H2O}∞, 5, which have been structurally characterized by X-ray crystallography. Complexes 1 and 2 manifest quintuple and double helices formed by zinc ions and L ligands, which are supported by 2,4-PDC2− and 1,3,5-HBTC2− anions, respectively, to construct the rare single-walled metal–organic nanotubes. Complex 3 shows 1D fish-bone chains and complexes 4 and 5 display 2D pleated grids with helical and looped carboxylate chains, respectively, supported by the L ligands. Complexes 1–3 represent a unique example of the polycarboxylate ligands showing a significant effect on folding and unfolding of the Zn(II) helical coordination polymers, and they are also important in determining the number of helices. The L ligands in 1, 2 and 4 adopt a bidentate bonding mode, and a unique monodentate bonding mode for the dipyridyl amide ligand is found in 3 and 5, resulting in various types of ligand conformations.

Synthesis, structures, and properties of alkali and alkaline earth coordination polymers based on V-shaped ligand

A series of metal coordination polymers, [Li2(OBA)] (1), [Na2(OBA)(H2O)] (2), [K(HOBA)] (3), [Rb(HOBA)] (4), [Cs(HOBA)] (5), [Mg(OBA)(H2O)2] (6), [Ca(OBA)(H2O)] (7), and [Sr(OBA)(H2O)] (8) (H2OBA = 4,4′-oxybisbenzoic acid), was synthesized from alkali and alkaline-earth metal salts and 4,4′-oxybisbenzoic acid by solvothermal reactions. Single crystal X-ray structure analysis revealed that compounds 1–5 and 7–8 are three-dimensional while complex 6 has a layered structure. The inorganic motifs, ranging from discrete octahedra (6), edge-sharing octahedral dimers (7), and straight one-dimensional inorganic chains (1 and 8) to two-dimensional inorganic layers (2–5), are connected through organic linkers and thus form neutral networks. High thermal stabilities were observed for compounds 1, 2, 6, 7, and 8 up to approximately 500 °C. Electrochemical measurements of 1 revealed a stabilized reversible capacity of approximately 100 mAh g−1 after more than 30 charge/discharge cycles.

Construction of N,N′-di(3-pyridyl)adipoamide-based Zn(II) and Cd(II) coordination networks by tuning the isomeric effect of polycarboxylate ligands

Eight new Zn(II) and Cd(II) coordination networks containing N,N′-di(3-pyridyl)adipoamide (L) and polycarboxylate ligands, {[Zn2(2,5-PDC)2(L)(H2O)2]·2H2O}∞ (H2PDC = 2,5-pyridinedicarboxylic acid), 1, [Zn2(2,6-PDC)2(L)]∞, 2, {[Zn2(3,4-PDC)2(L)(H2O)6]·4H2O}∞, 3, {[Cd(2,6-PDC)(L)(H2O)]·4H2O}∞, 4, [Zn(1,3,5-HBTC)()]∞ (H3BTC = benzenetricarboxylic acid), 5, {[Cd(1,2,3-HBTC)(L)(H2O)]·H2O}∞, 6, {[Cd2(1,3,5-HBTC)2(L)(H2O)2]·2H2O}∞, 7, and {[Zn3(1,2,4-BTC)2(L)(H2O)4]·4H2O}∞, 8, have been synthesized by hydrothermal reactions and characterized by single crystal X-ray crystallography. Structural analysis reveals that 1 and 2 form pleated hcb layers with 1D helical chains, in which the layers of 1 interdigitate with each other and those of 2 are linked by the π–π stacking interactions. Complexes 3 and 4 exhibit 1D ladders with single and double rungs, respectively, whereas 5 shows a 2D pleated net with the sql topology, 6 displays a 3D dia coordination network and 7 forms a 2D structure with the (63)(66)-3,4L88 topology. The BTC3− ligands in 8 adopt the μ4-bonding modes, resulting in a 3D coordination network with the rare (65·8)-hxg-d-4-P2/c topology. The various bonding modes, the ligand-isomerism of the polycarboxylate ligands and the identity of the metal center play important roles in determining the structural diversity. Their thermal and luminescent properties are also discussed.

N-(6-Methyl-2-pyrid-yl)formamide.

The molecule of the title compound, C7H8N2O, is essentially planar with a maximum deviation of 0.0439 (1) Å from the best plane. In the crystal, N—H⋯O hydrogen bonds between self-complementary amide groups join molecules into centrosymmetric dimers.

2-{5-[N-(2-Pyridyl)carbamo­yl]pentan­amido}pyridinium hexa­fluoro­phosphate

In the crystal structure of the title compound, C16H19N4O2 +·PF6 −, the cations and anions are situated on centres of inversion. Thus, the N—H H atom is disordered over both N atoms due to symmetry. In the crystal, molecules are connected via N—H⋯F and N—H⋯O hydrogen bonds. The cation adopts the ⋯AAA⋯ trans conformation in the solid state.

Poly[tetra­kis­(μ-benzene-1,2-dicarboxyl­ato)di-μ-formato-penta­strontium(II)]

The asymmetric unit of the title complex, [Sr5(C8H4O4)4(HCO2)2]n, contains three independent SrII ions, one of which is located on an inversion center. In the crystal, the SrII ions (coordination numbers 8, 9 and 12) are connected by two crystallographically distinct benzene-1,2-dicarboxylate ligands and one formate ligand, forming a two-dimensional polymer parallel to (001).

Poly[[aqua-(μ(5)-3,4,5,6-tetra-carb-oxy-cyclo-hexane-1,2-dicarboxyl-ato)strontium] monohydrate].

In the title compound, {[Sr(C12H10O12)(H2O)]·H2O}n, the SrII ion is coordinated by six O atoms of five symmetry-related 3,4,5,6-tetracarboxycyclohexane-1,2-dicarboxylate ligands and one water molecule in a slightly distorted monocapped trigonal–prismatic environment. The ligands bridge the SrII ions, forming a two-dimensional structure. In the crystal, O—H⋯O hydrogen bonds further connect the structure into a three-dimensional network. The H atoms of two of the carboxyl groups were refined as half-occupancy.

Poly[tetra­aqua­(μ8-butane-1,2,3,4-tetra­carboxyl­ato)distrontium]

In the title compound, [Sr2(C8H6O8)(H2O)4)]n, the SrII ion is coordinated by six O atoms of four symmetry-related ligands and two water molecules in a distorted bicapped trigonal–prismatic environment. The butane-1,2,3,4-tetracarboxylate ligands lie on inversion centers and bridge SrII ions, forming a three-dimensional network. Within the three-dimensional structure, there are O—H⋯O hydrogen bonds involving the water molecules and carboxylate O atoms.

5-Iodo-pyrimidin-2-amine.

The molecule of the title compound, C4H4IN3, has crystallographic mirror plane symmetry. In the crystal, the molecules are connected through N—H⋯N hydrogen bonds into polymeric tapes extended along the a axis, which are typical of 2-aminopyrimidines. Each molecule acts as a double donor and a double acceptor in the hydrogen bonding.