Chun-Jing Zhang

High-dimensional frameworks dependent on coordination mode of ligand controlled by acidity of reaction solution. Syntheses, structures, magnetic and fluorescence properties of eight new compounds

Eight new compounds [Ln4(HL)2(L)2(H2O)14(H2W12O40)]·nH2O (Ln = La (1), Pr (3), n = 14; Ce (2), n = 12; Nd (4), n = 17. HL− = acidic pyridine-2,6-dicarboxylate, L2− = pyridine-2,6-dicarboxylate) and [Ln3(HL)3(H2O)10(H2W12O40)]·10H2O (Ln = La (5), Ce (6), Pr (7), Nd (8)) were conventionally synthesized. Compounds 1–4 are isomorphic and show a 2D structure with (326272)(31425162)2 topology, and compounds 5–8 are also isomorphic and have a 3D framework constructed from [H2W12O40]6− clusters and lanthanide–organic–frameworks. Compounds 1 and 5, 2 and 6, 3 and 7, and 4 and 8 were obtained in the same solution systems, respectively. The formation of these compounds with two types of multidimensional structures mainly depends on the solution acidity and the coordination modes of the ligands. Furthermore, thermal properties of 1–8, fluorescence properties of 4 and 8, and magnetic properties of 2–4 have been examined.

Three 3D octamolybdate-based hybrids with 1D–3D CuI/CuII-bis(triazole) motifs: influence of the amount of Et3N

Three three-dimensional (3D) compounds constructed from octamolybdate clusters and 1D–3D CuI/CuII-bis(triazole) motifs, [CuI4(btx)4][β-Mo8O26] (1), [CuI4(btx)2][β-Mo8O26]·H2O (2), and [CuII2(btx)4][α-Mo8O26] (3) [btx = 1,6-bis(1,2,4-triazol-1-yl)hexane], were hydrothermally synthesized in the presence of different amounts of reducing agent Et3N. The crystal structures have been determined by X-ray diffraction. In 1, the copper(I)-btx motif is a 1D meso-helix chain which is further linked by hexadentate β-[Mo8O26]4−clustersvia coordinating to CuI cations to achieve an intricate 3D structure. In 2, the copper(I)-btx motif exhibits a 2D grid sheet, and the hexadentate β-[Mo8O26]4−clusters interact with neighboring sheets to construct a 3D structure. In 3, the copper(II)-btx motif possesses a 3D (4,4)-connected framework with the (65.8)(64.82) topology, which is further connected by the tetradentate α-[Mo8O26]4−clusters forming a 3D self-penetrating (4,6)-connected hybrid network. The thermal stability and luminescent properties of 1–3 are investigated in the solid state.

Syntheses, crystal structures, and properties of four new coordination compounds of transition metals and imidazoledicarboxylic acid derivatives

Four new transition metal coordination complexes, [Cd(H2pimdc)2(H2O)2] · 4H2O (1), [Zn(H2pimdc)2(H2O)2]2 · 7H2O (2), and [M(H2pimdc)2] (M = Cu (3) or Ni (4), H2pimdc− = 2-propyl-4,5-imidazoledicarboxylate), have been prepared by conventional synthesis and characterized by elemental analyses, IR, TG, and single-crystal X-ray diffraction. H2pimdc− is a bidentate chelating ligand in 1 and 2, leading to 3-D supramolecular structures through hydrogen bonds. However, H2pimdc− is a tridentate chelating-bridge ligand in 3 and 4, which exhibit 2-D layer structures. Thermal properties and photoluminescence spectra of 1–4 were measured.

Two organic–inorganic hybrids based on polyoxometalates: synthesis, crystal structure, and characterization

Two new Keggin- and Wells-Dawson-type polyoxometalate-based organic–inorganic hybrid copper–organonitrogen complexes have been synthesized under hydrothermal conditions: [CuI(4,4′-bpy)]2[H2SiW12O40] ⋅ 2H2O (4,4′-bpy = 4,4′-bipyridine) (1) and (en =ethylenediamine), and characterized by elemental analysis, IR spectra, TGA, XRD, and single crystal X-ray diffraction. In 1, [Cu(4,4′-bpy)]+ cations form polymeric chains and a weak Cu–O linkage makes the anions situate between two chains, forming an infinite 1-D ladder-chain structure. Such 1-D ladder-chains are further interconnected via hydrogen bonding into a 3-D supramolecular framework. Compound 2 with covalently bonded 3-D structure consists of saturated Wells-Dawson tungstoarsenate polyoxoanions and copper complexes with two types (rigid and flexible) of ligands. The polyoxoanion has the highest connectivity for Wells-Dawson tungstoarsenate polyoxoanion coordination polymers to date. XPS spectra indicate that three W atoms in the Dawson unit were reduced and that there coexist CuI and CuII in 2.

A water chain with trimeric/hexameric clusters trapped in a POM/Ln compound

A new 3-D supramolecular compound based on a Keggin polyoxometalate and lanthanide (Ln) coordination cations [Ce(H2O)3L3]2[HSiMo12O40]2[L] ⋅ 7H2O (1) (L = isonicotinic acid) has been synthesized and characterized by routine methods. Compound 1 has a water chain with trimeric and hexameric water clusters trapped in the network. The isonicotinic acid plays a key role in forming the 1-D water chains. Compound 1 shows intense photoluminescence at room temperature.

Synthesis, structure, and magnetism of four polyoxomolybdate compounds containing yttrium and ytterbium

Four new polyoxometalate compounds consisting of Anderson-type anions and trivalent rare earth (RE) cations, [RE 2 (H2O)14M(OH)6Mo6O18][M(OH)6Mo6O18] · 14H2O, RE = Y, M = Cr(1), Al(2); RE = Yb, M = Al(3), Cr(4), have been synthesized in aqueous solution and characterized by elemental analyses, infrared (IR) spectra, thermal gravimetric (TG) analyses, and single crystal X-ray diffraction. [M(OH)6Mo6O18]3− as a bidentate ligand coordinates to two RE 3 + , forming a double-supported cation [RE 2(H2O)14M(OH)6Mo6O18]3+. The cations and other [M(OH)6Mo6O18]3− anions in the crystals are linked via hydrogen bonding interactions tightly, forming four supramolecular compounds. The magnetic properties of 1, 3, and 4 have been examined by measuring their magnetic susceptibilities from 2 to 300 K.

Formation of [FeW12O40]5− under hydrothermal conditions: syntheses, crystal structures, and characterization of [Fe(2,2′-bipy)3]2[HFeW12O40] · 5H2O and (4,4′-H2bipy)6(Hpy)2(H3O)[FeW12O40]3 · 11H2O

Two supramolecular compounds based on tungstoferrate [FeW12O40]5−, [FeII(2,2′-bipy)3]2[HFeW12O40] · 5H2O (1), and [Hpy]2[4,4′-H2bipy]6(H3O)[FeW12O40]3 · 11H2O (2) (py = pyridine, bipy = bipyridine) were synthesized hydrothermally and characterized structurally. The hydrogen bonds between polyoxoanions and water and the edge-to-face π–π interaction between [FeII(2,2′-bipy)3]2+ with a shortest C–C distance of 3.513 Å are the main forces to construct the 3-D architecture of 1. In 2, a 3-D supramolecular architecture is assembled by the tungstoferrate anions, protonated 4,4′-bipy cations, and water through hydrogen bonding. The variable-temperature magnetic susceptibilities indicate that 1 is paramagnetic with μ eff corresponding to one Fe(III) with spin-only contribution, showing that Fe in the coordination cations has a +II oxidation number and low spin state.

Synthesis and Characterization of a Three-dimensional Porous Compound: [Cu(H2O)6][{Cu(H2O)2}2{Cu(H2O)4H4W12O42}] · 12H2O

A novel transition metal polyoxotungstate, [Cu(H2O)6][{Cu(H2O)2}2{Cu(H2O)4H4W12O42}] · 12H2O (1), has been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, IR and UV/vis spectroscopy, and TG analysis. The paradodecatungstate anions [H2W12O42]10− are linked by CuO6 octahedra, forming a three-dimensional (3D) structure. The magnetic susceptibility of compound 1 in the temperature range 2 - 300 K shows the presence of antiferromagnetic interactions within the uniform Cu2・ ・ ・Cu3 chains

Honeycomb-like layers constructed by hydrogen bonds. Synthesis, structure, and property of two new supramolecular compounds based on polyoxotungstate

Two new compounds based on polyoxotungstate [Co2(PCA)4(H2O)6][SiW12O40]·8H2O (1), [Cd2(PCA)4(H2O)6][SiW12O40]·8H2O (2) (PCA = pyridine-4-carboxylic acid) are prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectroscopy, and thermal analysis. The results of the single crystal X-ray diffraction analysis reveal that 1 and 2 are isomorphic and two water molecules in the compounds act as the bridging groups of two cobalt or cadmium atoms, forming dinuclear coordination cations. The ligand PCA adopts a monodentate coordination mode and its uncoordinated carboxyl oxygen atom and the protonized nitrogen atom form hydrogen bonds with other ligands, by which the cations are linked into a supramolecular 2D network with hexagonal grids. The polyoxotungstate anions are arranged above and below the cationic grids. A strong emission peak at 420 nm of 2 is attributed to a ligand-metal transition.

Two α-metatungstate compounds containing supramolecular helical chains

[Co(bipy)3]3[{Co(bipy)2(H2O)}2{H3W12O40}2] · H2O (1) and [H2bipy]0.5[{Cu(bipy)2}2{H3W12O40}] · H2O (2) (bipy = 2,2′-pyridine) have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and TG analyses. In 1, there exist supramolecular left/right-helical chains constructed by [Co1(bipy)3]2+ and these chains perpendicularly interact with a series of parallel POM double-chains composed of [{Co(bipy)2(H2O)}2{H3W12O40}2]6− anions and [Co2(bipy)3]2+ cations forming a 3-D supramolecular network. In 2, there also exist supramolecular left-/right-helical chains constructed by [{Cu(bipy)2}2{H3W12O40}]− fragments. Furthermore, these left-/right-helical chains are linked together via H-bonds forming interesting enantiomorphous chiral layers. Electrochemical properties of these compounds have been studied.