Zinc-based Coordination Polymer Research Articles

"Turn-on" Fluorescence Sensing and Discriminative Detection of Aliphatic Amines Using a 5-Fold-Interpenetrated Coordination Polymer.

A 5-fold-interpenetrated zinc-based coordination polymer can discriminately detect aliphatic amines through a fluorescence "turn-on" method. This compound can sense aliphatic amines in the solid state, solution state, and vapor phase. Theoretical calculations revealed that the ground-state dipole moment of the corresponding amines guides the order of enhancement.

Surfactant-Assisted Nanocrystalline Zinc Coordination Polymers: Controlled Particle Sizes and Synergistic Effects in Catalysis.

Different morphologies and particle sizes of two crystalline zinc-based coordination polymers (CPs), [Zn(pytz)H2 O]n (1; H2 pytz=2,6-bis(tetrazole)pyridine) and [Zn2 (pytz)2 4 H2 O] (2), from the bulk scale to the nanoscale, could be obtained under solvothermal conditions with different surfactants (polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG) 2000) as templates. PVP and PEG 2000 could act as capping and structure-directing agents, respectively, to influence the growth of crystalline particles and control their sizes. CP 1 exhibits a two-dimensional framework with window-like units and 2 shows a bimetallic structure. Nanocrystalline 1 and 2 were used as heterogeneous catalysts to study how adjacent catalytic active sites synergistically effected their catalytic reactivities in the direct catalytic conversion of aromatic dinitriles into oxazolines. The results showed that 1 produced bis-oxazolines as the sole products, whereas 2 gave the mono-oxazolines as the major products under the same reaction conditions.

A three-dimensional zinc-based coordination polymer built from 5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium with a 4-connected sra topology.

A novel three-dimensional Zn(II) complex, poly[aqua(μ4-5-carboxylato-1-carboxylatomethyl-2-oxidopyridinium)zinc(II)], [Zn(C8H5NO4)(H2O)]n, has been prepared by hydrothermal assembly of Zn(CH3COO)2·2H2O and 5-carboxy-1-(carboxymethyl)pyridin-1-ium-2-olate (H2ccop). The ccop(2-) anions bridge the Zn(II) cations in a head-to-tail fashion via monodentate aromatic carboxylate and phenolate O atoms to form an extended zigzag chain which runs parallel to the [011] direction. One O atom of the aliphatic carboxylate group of the ccop(2-) ligand coordinates to the Zn(II) atom of a neighbouring chain thereby producing undulating layers which lie parallel to the (01-1) plane. A similar parallel undulating planar structure can be obtained if a path involving the other O atom of the aliphatic carboxylate group is considered. Thus, the aliphatic carboxylate group acts in a bridging bidentate mode to give extended -Zn-O-C-O-Zn- sequences running parallel to [001] which link the layers into an overall three-dimensional framework. The three-dimensional framework can be simplified as a 4-connected sra topology with a Schläfli symbol of 4(2).6(3).8 if all the Zn(II) centres and ccop(2-) anions are regarded as tetrahedral 4-connected nodes. The three-dimensional luminescence spectrum was measured at room temperature with excitation and emission wavelengths of 344-354 and 360-630 nm, respectively, at intervals of 0.15 and 2 nm, respectively.

Influence of the counter anion and steric hindrance of pyrazolyl and imidazolyl flexible ligands on the structure of zinc-based coordination polymers

Treatments of flexible 1,4-bis(3,5-dimethylpyrazolyl)butane (bbd), 1,4-bis(imidazolyl)butane (bib) and 1,4-bis(2-methylimidazolyl)butane (bmib) ligands with zinc salts at room temperature, resulted in the formation of four novel metal–organic coordination architectures: [ZnI2(μ-bbd)]n (1), [Zn(NCS)2(μ-bbd)]n (2), {[Zn(μ-bib)2](ClO4)2·(Et2O)0.5·(H2O)0.25}n (3) and {[Zn(μ-bmib)2](ClO4)2·(H2O)4}n (4). X-ray crystallographic analyses show different 1D and 3D polymeric structures for compounds 1–4 due to the variation of the counter anions, solvent, steric hindrance and position of donating atoms in the structure of flexible ligands. In 1 and 2, one-dimensional (1D) zig-zag polymeric chains are formed via metal centers and μ-bbd ligands. Complex 3 shows a 3-fold interpenetrated 3D architecture with 103-ths network topology. In contrast to 3, in the structure of 4 neighboring Zn(II) ions are interconnected by a double-bridging μ-bmib ligands to form an infinite 1D polymeric double chain. The conformations of the flexible ligands were analyzed in detail.

Synthesis, Crystal Structure and Catalytic Behavior of Homo- and Heteronuclear Coordination Polymers [M(tdc)(bpy)] (M2+ = Fe2+, Co2+, Zn2+, Cd2+; tdc2– = 2,5-thiophenedicarboxylate)

A series of isostructural 3D coordination polymers (3)∞[M(tdc)(bpy)] (M(2+) = Zn(2+), Cd(2+), Co(2+), Fe(2+); tdc(2-) = 2,5-thiophenedicarboxylate; bpy = 4,4'-bipyridine) was synthesized and characterized by X-ray diffraction, thermal analysis, and gas adsorption measurements. The materials show high thermal stability up to approximately 400 °C and a solvent induced phase transition. Single crystal X-ray structure determination was successfully performed for all compounds after the phase transition. In the zinc-based coordination polymer, various amounts of a second type of metal ions such as Co(2+) or Fe(2+) could be incorporated. Furthermore, the catalytic behavior of the homo- and heteronuclear 3D coordination polymers in an oxidation model reaction was investigated.

Characteristic Differences in the Formation of Complex Coacervate Core Micelles from Neodymium and Zinc-Based Coordination Polymers

In this paper we compare the formation of complex coacervate core micelles (C3Ms) from two different tricompontent mixtures, namely neodymium, the bisligand L2EO4 and the poly(cation)-block-poly(neutral) diblock copolymer P2MVP41-b-PEO205, and zinc, L2EO4 and P2MVP41-b-PEO205 mixed systems. Three sets of titration experiments were carried out for each system: (i) titration of diblock copolymer P2MVP41-b-PEO205 with the stoichiometric mixture of metal ions and bisligands, (ii) titration of a mixture of diblock copolymer and bisligand with metal ions, and (iii) titration of a mixture of diblock copolymer and metal ions with bisligands. In all the above three cases, micelles are found to form either in a broad range of charge ratios or in a broad range of metal/bisligand ratios. Upon addition of Nd2-(L2EO4)3 coordination polymer to P2MVP41-b-PEO205 solution, and upon addition of Nd3+ to a mixture of L2EO4 and P2MVP41-b-PEO205, micelles are found to form immediately after the first addition, whereas micelles show up in the similar zinc system only after a certain threshold Zn-(L2EO4) or Zn2+ concentration. This difference can be traced to the different structures of the Nd2-(L2EO4)3 and Zn-(L2EO4) coordination compounds. At very low concentrations, Zn-(L2EO4) are ring-like oligomers, but Nd2-(L2EO4)3 are larger networks. The network structure favors the formation of coacervate micellar core with P2MVP41-b-PEO205. Moreover, excess of Nd3+ ions will break up the C3Ms, while the same amount of Zn2+ has hardly any effect on the C3Ms. The breakdown of C3Ms by Nd3+ is due to the charge inversion of the coordination complex with increasing [Nd3+]/[L2EO4] ratio, which results in repulsive interaction between the coordination complex and the diblock copolymer, whereas no such interaction can occur in the zinc system.

One-dimensional zinc-based coordination polymers incorporating cyanate anions

Two one-dimensional zinc-based coordination polymers containing cyanate anions are reported. catena-Poly[sodium [[tricyanatozinc(II)]-mu-1,4-diazabicyclo[2.2.2]octane-kappa2N:N']], [Na[Zn(NCO)3(C6H12N2)]]n, consists of linear [tricyanatozinc(II)]-mu-1,4-diazabicyclo[2.2.2]octane strands in which the Zn2+ cations adopt trigonal-bipyramidal coordination on sites of -6m2 point symmetry. Na+ cations lie between the strands on sites of -3m point symmetry, coordinated in a distorted octahedral geometry by six O atoms of the cyanate anions. catena-Poly[[dicyanatozinc(II)]-mu-4,4'-bipyridine-kappa2N:N'], [Zn(NCO)2(C10H8N2)]n, crystallizes in the space group P2(1)/n with Z' = 5. The structure consists of zigzag strands formed by Zn2+ cations linked via 4,4'-bipyridine. Each Zn2+ cation adopts a tetrahedral coordination, with two sites occupied by 4,4'-bipyridine and two cyanate anions completing the coordination sphere. The structure is closely comparable with the thiocyanate and halide analogues [ZnX2(C10H8N2)] (X = NCS, Cl or Br).

Preparation, characterization, and X-ray crystal structures of helical and syndiotactic zinc-based coordination polymers.

The reactions of (facac)2Zn.2H2O (facac = 1,1,1,5,5,5-hexafluoroacetylacetonate) with 2,5-bis(4-ethynylpyridyl)furan (1) and 1,2-bis(4-ethynylpyridyl)benzene (2) yield, upon crystallization, coordination polymers. The former polymer, ((facac)2Zn.1)n, has an isotactic, helical structure in the solid state [monoclinic space group P2(1)/n; a = 11.0374(3) A, b = 24.2179(10) A, c = 14.3970(4) A, beta = 92.880(2) degrees; Z = 4]. The latter polymer, ((facac)2Zn.2)n, adopts a syndiotactic structure in the solid state [monoclinic space group P2(1)/n; a = 9.1344(1) A, b = 21.7985(5) A, c = 16.0322(4) A, beta = 99.6680(11) degrees; Z = 4]. The solution structures of the corresponding oligomers have been studied by low-temperature 1H and 19F NMR spectroscopy. Chiral polymers were prepared using the fragment [(+)-tfc]2Zn ((+)-tfc = 3-((trifluoromethyl)hydroxymethylene)-(+)-camphorate). A linear, zigzag structure was found for ([(+)-tfc]2Zn.1)n [triclinic space group P1; a = 7.4833(2) A, b = 14.1563(5) A, c = 21.21230(5) A, alpha = 78.4440(15) degrees, beta = 81.5644(15) degrees, gamma = 76.4976(13) degrees; Z = 1]. Reaction with tris(4-pyridyl)methanol (3) yielded a homochiral, helical polymer, ([(+)-tfc]2Zn.3)n [monoclinic space group C2; a = 25.0633(12) A, b = 11.8768(7) A, c = 17.1205(9) A, alpha = 90 degrees, beta = 117.954(3) degrees, gamma = 90 degrees; Z = 4].