Ya-Guang Chen

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.

Synthesis and characterization of novel heteropoly-tungstoarsenates containing lanthanides [LnAs4W40O140]25− and their biological activity

Abstract A series of lanthanide polyoxoanions [LnAs4W40O140]25− (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy or Yb) have been prepared from the cryptate anion [NaAs4W40O140]27− and lanthanides and characterized by elemental analysis, 183W NMR, emission spectra. A number of evidences indicate that the lanthanides occupy the central site in the complexes. The title complexes display anti-tumor activity in vitro and in vivo.

A 9-connected metal–organic framework with gas adsorption properties

A 9-connected, trinuclear cluster-based microporous metal–organic framework, Ni3(OH)(Ina)3(BDC)1.5 (Ina = isonicotinate and BDC = 1,4-benzenedicarboxylate) (1), was synthesized and characterized. The structure is constructed from a 3D channel and two kinds of cages (tetrahedron and triangular pyramid cages). Compound 1 is microporous with a BET surface area of 1255 m2 g−1. It has been observed that the amount of adsorbed benzene (22.60%) is much higher than that of cyclohexane (1.40%), showing its potential to separate benzene and cyclohexane.

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.

A new compound constructed from Keggin anions and Cu-5,6-diamino-1,10-phenanthroline complexes: synthesis, structure, and characterization

A new inorganic–organic hybrid based on polyoxometalate, [Cu2(daphen)2(H2O)4(PW11WVO40)] · 6H2O (1) (daphen = 5,6-diamino-1,10-phenanthroline), was synthesized hydrothermally and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermal analysis. Single-crystal X-ray diffraction analysis reveals that in 1 the Keggin anion [PW12O40]4− is tetradentate, linking four Cu(II)-daphen fragments with its four terminal oxygen atoms in a plane; Cu2+ is coordinated by two terminal oxygen atoms of two [PW12O40]4− anions, two water molecules, and two nitrogen atoms of the phen ring of a daphen, forming a polymeric layer. The 3-D architecture of the compound is further formed via hydrogen bonds between these layers. The daphen is bidentate chelating and does not participate in formation of hydrogen bonds. Redox of 1 was examined.

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.

Two Compounds Constructed from Bimolybdenum-Capped Sandwich-Type Tetra-Ni-molybdogermanate and N-Donor Multidentate Ligand

Two organic-inorganic hybrid bimolybdenum-capped tetra-Ni(II) sandwich-type molybdogermanates, namely, (H2L)4[Ni4(H2O)2{B-α-GeMo9O34 (MoO2)}2]·6H2O (1), [Ni2(HL)4(H2O)2][Ni4(H2O)2{B-α-GeMo9O34(MoO2)}2]·12H2O (2), L = 2,4,5-tri(4-pyridyl)imidazole, were prepared with hydrothermal synthesis method and characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, thermogravimetric analysis, and single-crystal X-ray diffraction. Their magnetic properties and electrochemical properties were investigated. The results show that compounds 1 and 2 contain a new bimolybdenum-capped sandwich-type heteropolymolybdate anion, [Ni4(H2O)2{B-α-GeMo9O34(MoO2)}2](8-). The compound 1 is a zero-dimensional supramolecular compound, and the supramolecular architecture of compound 2 is constructed from covalent layers through hydrogen bonds and π-π interaction. The two compounds both present electrocatalytic activities for the reduction of nitrite.

Syntheses, structures and properties of three neutral bisupporting heteropolyoxometalates

Three neutral polyoxometalates [PVW11O40{M(phen)2H2O}2] · 3H2O (phen = 1,10′-phenanthroline, M=Co 1, Zn 2, Ni 3) are composed of water and the neutral Keggin-type polyoxometallate covalently linking a pair of transition metal complex fragments on opposite sides. The transition metal lies in the center of a distorted octahedron. Multi hydrogen-bonding interactions between coordinated waters of neutral polyoxometalate molecules and terminal oxygen atoms of Keggin units and between bridging oxygens of Keggin units and lattice water create a two dimensional layer and between the layers there exist van der Waals forces. The framework of the neutral molecule begins to decompose at ca 500°C. Compound 1 exhibits a weak antiferromagnetic interaction in the 2–300 K range.

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.