Structural diversity and photocatalytic properties of Cd(II) coordination polymers constructed by a flexible V-shaped bipyridyl benzene ligand and dicarboxylate derivatives.

Hydrothermal reactions of Cd(OAc)2·2H2O with a flexible V-shaped bipyridyl benzene ligand and five benzenedicarboxylic acid derivatives gave rise to five new coordination polymers i.e., [Cd(1,4-BDC)(bpmb)(H2O)]n (1), {[Cd(1,3-BDC)(bpmb)]·0.125H2O}n (2), [Cd2(5-Me-1,3-BDC)2(bpmb)2]n (3), [Cd(5-NO2-1,3-BDC)(bpmb)(H2O)]n (4) and [Cd(5-OH-1,3-BDC)(bpmb)(H2O)]n (5) (bpmb = 1,3-bis(pyridine-3-ylmethoxy)benzene, 1,4-H2BDC = 1,4-benzenedicarboxylic acid, 1,3-H2BDC = 1,3-benzenedicarboxylic acid, 5-Me-1,3-H2BDC = 5-methyl-1,3-benzenedicarboxylic acid, 5-NO2-1,3-H2BDC = 5-nitro-1,3-benzenedicarboxylic acid, 5-OH-1,3-H2BDC = 5-hydroxy-1,3-benzenedicarboxylic acid). Their structures have been determined by single-crystal X-ray diffraction analyses, elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and thermogravimetric analyses (TGA). Compound 1 is a two-fold interpenetrating network showing the coexistence of polyrotaxane and polycatenane characters. Compounds 2 and 3 exhibit similar 2D (3,5)-connected (4(2)·6(7)·8)(4(2)·6) nets in which the bpmb ligands work as lockers in interlocking 1D [Cd(1,3-BDC/5-Me-1,3-BDC)]n chains. Compound 4 shows a 2D 4-connected (6(6)) sandwich-like structure with differently oriented [Cd(5-NO2-1,3-BDC)]n chains. Compound 5 is a 3D supramolecular pcu net based on a 1D ladder-shaped chain. These results suggest that the substituted positions of carboxylate groups and changes in substituted R groups in the 5-position of BDC ligands have significant effect on the final structures. These compounds exhibited relatively good photocatalytic activity towards the degradation of methylene blue (MB) in aqueous solution under UV irradiation. Moreover, solid-state photoluminescence properties of 1-5 were also investigated.

A helical zinc(II) coordination polymer assembled from 1,3-bis[(pyridin-3-yl)methoxy]benzene and benzene-1,4-dicarboxylic acid.

In catena-poly[[aqua[1,3-bis(pyridine-3-ylmethoxy)benzene-κN]zinc(II)]-µ2-benzene-1,4-dicarboxylato-κ(2)O(1):O(4)], [Zn(C8H4O4)(C18H16N2O2)(H2O)]n, each Zn(II) centre is tetrahedrally coordinated by two O atoms of bridging carboxylate groups from two benzene-1,4-dicarboxylate anions (denoted L(2-)), one O atom from a water molecule and one N atom from a 1,3-bis[(pyridin-3-yl)methoxy]benzene ligand (denoted bpmb). (Aqua)O-H···N hydrogen-bonding interactions induce the formation of one-dimensional helical [Zn(L)(bpmb)(H2O)]n chains which are interlinked through (aqua)O-H···O hydrogen-bonding interactions, producing two-dimensional corrugated sheets.

Regioselective C-H imidation of five-membered heterocyclic compounds through a metal catalytic or organocatalytic approach.

An efficient method for the synthesis of 2-amino and ß-amino five-membered heterocyclic derivatives that are closely related to a variety of biologically active natural products is described. Regioselectivity was achieved through a metal catalytic or organocatalytic approach. Preliminary studies on the reaction mechanism suggest a radical imidation pathway; however, further studies are needed to verify the mechanism.

The three-dimensional coordination polymer poly[[aqua[µ4-2,2'-(diazene-1,2-diyl)dibenzoato]lead(II)] 1,2-bis(pyridin-4-yl)ethylene hemisolvate].

A novel three-dimensional coordination polymer, {[Pb(C14H8N2O4)(H2O)]·0.5C12H10N2}n, has been synthesized by hydrothermal reaction of Pb(OAc)2·3H2O (OAc is acetate), 2,2'-(diazene-1,2-diyl)dibenzoic acid (H2L) and 1,2-bis(pyridin-4-yl)ethylene (bpe). The asymmetric unit contains a crystallographically independent Pb(II) cation, one L(2-) ligand, an aqua ligand and half a bpe molecule. Each Pb(II) centre is seven-coordinated by six O atoms of bridging-chelating carboxylate groups from L(2-) ligands and by one O atom from a coordinated water molecule. The Pb(II) cations are bridged by L(2-) ligands, forming [PbO2]n chains along the a axis. These chains are further connected by L(2-) ligands along the b and c axes to give a three-dimensional framework with a 4(12)6(3) topology. The channel voids are occupied by bpe molecules.

Three coordination polymers constructed from various polynuclear clusters spaced by 2,2'-azodibenzoic acid: syntheses and fluorescent properties.

Solvothermal reactions of M(OAc)2·2H2O (M = Zn, Cd, Pb) with 2,2'-azodibenzoic acid (H2L) in MeOH-H2O (MeOH = methanol) at 120 °C gave rise to three coordination polymers, [Zn12(µ4-O)3L9]n (1), [CdL(H2O)]n (2) and [Pb3(µ4-O)L2]n (3). Compounds 1-3 are characterized by elemental analysis, IR, powder X-ray diffraction and single-crystal X-ray diffraction. Compound 1 has two similar tetranuclear [Zn4(µ4-O)(µ2-CO2)6] units as nodes and displays an intriguing three-dimensional (3D) 6-connected network with a 4(12)6(3) topology. Compound 2 exhibits a 3D framework constructed by linking infinite helical Cd-carboxylate chains through L ligands. Compound 3 holds a 3D structure in which each hexanuclear [Pb6(µ4-O)2(CO2)4] unit works as a six-connecting node to connect its equivalent ones via sharing L ligands. In addition, the fluorescent properties and thermal stabilities of 1-3 were also investigated.

Electrochemical detection of ß-amyloid peptides on electrode covered with N-terminus-specific antibody based on electrocatalytic O2 reduction by Aß(1-16)-heme-modified gold nanoparticles.

ß-Amyloid (Aß) peptides are believed to be important for the diagnosis and prognosis of Alzheimer's disease (AD) serving as reliable molecular biomarkers. In this work, we reported a simple and sensitive electrochemical strategy for the detection of total Aß peptides using gold nanoparticles modified with Aß(1-16)-heme (denoted as Aß(1-16)-heme-AuNPs). Monoclonal antibody (mAb) specific to the common N-terminus of Aß was immobilized onto gold electrode for the capture of Aß(1-16)-heme-AuNPs. The anchored Aß(1-16)-heme-AuNPs showed strong electrocatalytic O2 reduction. Pre-incubation of the mAb-covered electrode with native Aß decreased the amount of Aß(1-16)-heme-AuNPs immobilized onto the electrode, resulting in the decrease of the reduction current of O2 to H2O2. The competitive assay is sensitive and selective to Aß peptides. The voltammetric responses were found to be proportional to the concentrations of Aß ranging from 0.02 to 1.50nM, and a detection limit of 10 pM was achieved. To demonstrate the viability of the method for the analysis of Aß in real sample, artificial cerebrospinal fluid (aCSF) containing Aß(1-40), Aß(1-42) and Aß(1-16) was tested. We believe that the method would offer a useful means for quantifying Aß in a biological matrix, and be valuable in the design of new types of electrochemical biosensors for the detection of peptides and proteins.

Assembly and spontaneous resolution of the chiral inorganic polyoxometalates-based frameworks via helical chains association.

Two pairs of enantiomerically pure three-dimensional (3D) chiral polyoxometalate (POM) framework materials l,d-[K(H2O)]6·[H2GeW12O40]3·35H2O (1a and 1b) and l,d-[K(H2O)]6·[H2SiW12O40]3·29H2O (2a and 2b) based on inorganic achiral building blocks, have been synthesized and characterized by X-ray crystallography, elemental analysis, powder X-ray diffraction (PXRD), UV-Vis spectroscopy, circular dichroism (CD) spectra. Single-crystal X-ray diffraction analyses revealed that 1a and 1b, 2a and 2b are enantiomers, respectively. In 1a and 1b, 2a and 2b, {K(H2O)}n link terminal oxygen and µ2-bridging oxygen of Keggin-type polyanion moieties to generate 1D 31 helical infinite chiral chains, which are further connected by the achiral Keggin-type polyoxoanions to form 3D 4,8-connected chiral self-assembly frameworks with {4(12)·6(10)·8(6)}{4(6)}2 topology. 1 and 2 are isostructural. They are obtained by spontaneous resolution upon crystallization in the absence of any chiral source. They represent new examples of chiral self-penetrating pure inorganic frameworks known for POM systems. Compounds 1 and 2 display adsorption activity toward volatile organic compounds (VOCs).

A polyhedron-based metal-organic framework with a reo-e net.

A polyhedron-based metal-organic framework has been designed and constructed with a reo-e net, which is constructed from trinuclear nickel clusters and mixed ligands (copolymerization pattern). It comprises three kinds of polyhedra, which are the hexahedron, cuboctahedron and rhombicuboctahedron.

A sodalite-type porous metal-organic framework with polyoxometalate templates: adsorption and decomposition of dimethyl methylphosphonate.

A sodalite-type porous metal-organic framework with polyoxometalate templates, H(3)[(Cu(4)Cl)(3)(BTC)(8)](2)[PW(12)O(40)]·(C(4)H(12)N)(6)·3H(2)O (NENU-11; BTC = 1,3,5-benzenetricarboxylate), was obtained by a hydrothermal reaction. As a reasonable candidate for eliminating nerve gas, NENU-11 displays good adsorption behavior for dimethyl methylphosphonate (15.5 molecules per formula unit). In virtue of the catalytic activity of polyoxometalate guests, this nerve gas mimic could be facilely decomposed by a hydrolysis reaction.

Reactivity of polyoxoniobates in acidic solution: controllable assembly and disassembly based on niobium-substituted germanotungstates.

The reactivity of polyoxoniobates has been studied in acidic solution by grafting niobium onto trivacant Keggin-type germanotungstates. Four niobium-containing compounds were obtained in the course of this study. Cs(6.5)K(0.5)[GeW(9)(NbO(2))(3)O(37)]·6H(2)O (Cs(6.5)K(0.5)-1) synthesized by the reaction of K(7)H[Nb(6)O(19)] and A-α-Na(10)[GeW(9)0(34)] in H(2)O(2) solution is a tris(peroxoniobium)-substituted A-α-GeW(9) derivative. Cs(6.5)K(0.5)[GeW(9)Nb(3)O(40)]·10H(2)O (Cs(6.5)K(0.5)-2) is a peroxo-free compound obtained by eliminating the peroxo groups in 1. Monomers 1 and 2 as precursors can each afford two nanoscale POMs, dimer Cs(5)[H(15)Ge(2)W(18)Nb(8)O(88)]·18H(2)O (Cs(5)-3) and tetramer Cs(8)K(3)H(9)[Ge(4)W(36)Nb(16)O(166)]·27H(2)O (Cs(8)K(3)H(9)-4), through the formation of Nb-O-Nb bridges. Disassembly through the cleavage of Nb-O-Nb bonds from 4 to 2 and 1 was achieved by controlling the pH and by adding H(2)O(2), respectively. The transition from 1 to 2 can be achieved by simply adding H(2)O(2) to a solution of 1. All four compounds were characterized in the solid state by elemental analysis, infrared spectroscopy, thermogravimetry, and single-crystal X-ray diffraction. (183)W NMR analysis proved that the solid-state structures of polyanions 1-4 were retained after dissolution. Disassembly from 4 to 1 and 2 in solution was observed by (183)W NMR spectroscopy. The UV/Vis spectra of 1 at different pH confirmed that it is stable in the pH range of 0.1-14.0 at room temperature.

Coordination between [H2P2W12O48]12- and antimony(III): synthesis and characterization of sandwich complex derived from the new {P2W13O51} fragment.

A sandwich-type anionic cluster of a new lacunary building block [P(2)W(13)O(51)](14-) has been prepared: [H(6){P(2)W(13)O(51)}(2)Sb(4)](10-) (1) was synthesized in a one-pot self-assembly reaction of [H(2)P(2)W(12)O(48)](12-) with C(4)H(4)KO(7)Sb.0.5H(2)O and characterized by single-crystal X-ray analysis, IR, thermogravimetric analysis, elemental analysis, UV, NMR and electrochemistry. 1 represents the first dimetric, antimony-containing polyoxoanion derived from a vacant Dawson-type tungstophosphate.