A Series of Polyoxometalate-Viologen Photochromic Materials for UV Probing, Amine Detecting and Inkless and Erasable Printing.

In this work, by using two kinds of viologen ligands three POM-based Compounds were obtained under hydrothermal conditions, namely [AgI (bmypd)0.5 (ß-Mo8 O26 )0.5 ] (1) (bmypd ⋅ 2Cl=1,1'-[Biphenyl-4,4'-bis(methylene)]bis(4,4'-bipyridyinium)dichloride), [AgI 2 (bypy)4 (HSiW12 O40 )2 ] ⋅ 14H2 O (2) and [AgI (bypy)(γ-Mo8 O26 )0.5 ] (3) (bypy⋅Cl=1-Benzyl-4,4'-bipyridyinium chloride). The structures were characterized by Fourier transform infrared spectroscopy (FT-IR), Powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS) and single crystal X-ray diffraction. Compounds 1-3 show excellent photochromic ability with fast photoresponse under the irradiation of ultraviolet light with different degrees of color changes. So compounds 1-3 can be used as visible ultraviolet detectors. Compounds 1-3 also possess photoluminescence properties with fast and excellent fluorescence quenching effect. Compounds 1-3 also can be used as inkless and erasable printing materials with suspensions of 1-3 applied to filter paper. Compounds 1-3 can also produce color changes in amine vapor environment, especially in an NH3 atmosphere. Compounds 1-3 can be used as organic amine detectors.

Electrocatalytic and Hg2+ Fluorescence Identifiable Bifunctional Sensors for a Series of Keggin Compounds.

By using a 2,2'-dimethyl-4,4'-bithiazole (dm4bt) ligand, Keggin polyanions, and different metal ions, nine Keggin-based compounds, namely, {[Ag(dm4bt)2][Ag2(dm4bt)3]}2(PW12O40)(H2PWV2WVI10O40) (1), [CuI(dm4bt)2][CuII(dm4bt)2(PW12O40)] (2), [CuI(dm4bt)2]4(SiW12O40) (3), {[Zn(dm4bt)2]2(SiW12O40)} (4), [Zn(dm4bt)2(H2O)]2(HPMoV2MoVI10O40)·2H2O (5), [Zn(dm4bt)2(Mo2O7)] (6), [Cd(dm4bt)3][Cd(dm4bt)2(H2O)(PMo12O40)]2·2H2O (7), [Cd(dm4bt)3](PMo12O40)·(Hdm4bt) (8), and [Cd(dm4bt)2(H2O)2]2(HPMoV2MoVI10O40)·2H2O (9), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis, IR spectroscopy, and elemental analyses. Compounds 1-9 are zero-dimensional structures except compound 6, which exhibits a one-dimensional structure. In compound 1, there are three isolated subunits: Keggin anions, binuclear [Ag2(dm4bt)3]2+, and mononuclear [Ag(dm4bt)2]+ clusters. The binuclear [Ag2(dm4bt)3]2+ cluster has a Ag-Ag bond. In compound 2, a monosupporting anion {[CuII(dm4bt)2](PW12O40)}- and an isolated [Cu(dm4bt)2]+ cluster exist. By changing the transition metal ions, we obtained two different structures: a supramolecular 3 and a bisupporting anion in 4. By a one-pot method, we successfully obtained compounds 5 and 6, 7 and 8, respectively. In compound 5, the [Zn(dm4bt)2(H2O)]2+ subunit links adjacent PMo12 anions via S···O interactions to form a one-dimensional (1D) supramolecular chain. In compound 6, some PMo12 ions have transformed to [Mo2O7] n2 n- chains. The [Zn(dm4bt)2]2+ clusters buckle up and down the chain. Compound 7 has a monosupporting anion and an isolated [Cd(dm4bt)3]2+ cluster. Compound 8 has isolated anions and [Cd(dm4bt)3]2+ clusters. By changing the pH of 7 and 8, a distinct supramolecular compound 9 was obtained. Additionally, the optical band gap, electrochemical, and photocatalytic properties of 1-9 have been investigated in detail. The carbon paste electrodes can be used as bifunctional amperometric and fluorescence sensors for recognition of Hg2+. The n-CPEs as electrochemical sensors can show accurate selectivity for NO2- ions in some common ions. In the fluorescence sensor experiment, fluorescence intensities decrease more than 80% when quenched by Hg2+.

Systematic Investigation of Reaction-Time Dependence of Three Series of Copper-Lanthanide/Lanthanide Coordination Polymers: Syntheses, Structures, Photoluminescence, and Magnetism.

Three series of copper-lanthanide/lanthanide coordination polymers (CPs) Ln(III) Cu(II) Cu(I) (bct)3 (H2 O)2 [Ln=La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Er (10), Yb (11), and Lu (12), H2 bct=2,5-bis(carboxymethylmercapto)-1,3,4-thiadiazole acid], Ln(III) Cu(I) (bct)2 [Ln=Ce (2 a), Pr (3 a), Nd (4 a), Sm (5 a), Eu (6 a), Gd (7 a), Tb (8 a), Dy (9 a), Er (10 a), Yb (11 a), and Lu (12 a)], and Ln(III) 2 (bct)3 (H2 O)5 [Ln=La (1 b), Ce (2 b), Pr (3 b), Nd (4 b), Sm (5 b), Eu (6 b), Gd (7 b), Tb (8 b), and Dy (9 b)] have been successfully constructed under hydrothermal conditions by modulating the reaction time. Structural characterization has revealed that CPs 1-12 possess a unique one-dimensional (1D) strip-shaped structure containing two types of double-helical chains and a double-helical channel. CPs 2 a-12 a show a three-dimensional (3D) framework formed by Cu(I) linking two types of homochiral layers with double-helical channels. CPs 1 b-9 b exhibit a 3D framework with single-helical channels. CPs 6 b and 8 b display visible red and green luminescence of the Eu(III) and Tb(III) ions, respectively, sensitized by the bct ligand, and microsecond-level lifetimes. CP 8 b shows a rare magnetic transition between short-range ferromagnetic ordering at 110 K and long-range ferromagnetic ordering below 10 K. CPs 9 a and 9 b display field-induced single-chain magnet (SCM) and/or single-molecule magnet (SMM) behaviors, with Ueff values of 51.7 and 36.5 K, respectively.

Three multi-nuclear clusters and one infinite chain induced by a pendant 4-butyl-1H-pyrazole ligand for modification of Keggin anions.

By utilizing pendant 4-butyl-1H-pyrazole (Hbpz) with an alkyl "tail"--(CH2)3CH3, four Keggin-based complexes containing different transition metal multi-nuclear clusters and an infinite chain were hydrothermally synthesized and structurally characterized, [Cu(I)4(bpz)4(pz)2(H6PW11Cu(II)O39)2]·10H2O (1), [Cu(II)2(bpz)2(H2O)2(H3PCu0.5Mo11.5O40)]·3H2O (2), [Ag3(bpz)2(pz)(H4SiW12O40)]·4H2O (3) and [Ag5(bpz)4(H5/2PMo12O40)2]·6H2O (4) (pz = pyrazole). Compound 1 contains a tetra-nuclear cluster [Cu(I)4(bpz)4(pz)2](2-), in which four Cu(I) ions are fixed by four bpz and two pz ligands. These clusters are linked by Keggin anion dimers to form a 2D layer. In compound 2, the ptz ligands fuse the Cu(II) ions and an infinite 1D metal-organic chain is constructed with the Keggin anions hanging up and down covalently. Compound 3 has a planar triangle tri-nuclear cycle [Ag3(bpz)2(pz)] with three Ag(I) as cores. These cycles build a 3D framework of 3 through the further linkages of Keggin anions and Ag-Ag bonds. In compound 4, there exist discrete [Ag5(bpz)4](+) clusters with four bpz ligands fused by five Ag(I) cores, which are linked by Keggin anions alternately to form a 1D chain. Adjacent chains share the Ag-O bonds and a 2D layer is constructed. The bpz ligand is firstly introduced into the POM field and its successive two N donors are essential for the construction of multi-nuclear clusters and an infinite chain of 1-4. Additionally, the electrochemical and photocatalytic properties of the title compounds have been investigated.

Unprecedented application of flexible bis(pyridyl-tetrazole) ligands to construct helix/loop subunits to modify polyoxometalate anions.

By introducing the unprecedented and flexible isomeric bis(pyridyl-tetrazole) ligands into a polyoxometalates (POMs) system, three POM-based compounds, {Ag2(4-bptzb)2(H2O)2[H2PMo12O40]2}·4-bptzb·5H2O (1), [Ag4(3-bptzb)2(PMo(V)Mo(VI)11O40)]·2H2O (2), and Ag3(3-bptzb)2.5(H2O)2[H3P2W18O62] (3) [4-bptzb = 1,4-bis(5-(4-pyridyl)tetrazolyl)butane and 3-bptzb =1,4-bis(5-(3-pyridyl)tetrazolyl)butane], were synthesized under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses. Compound 1 exhibits a dimeric structure constructed from two Keggin [PMo12O40](3-) anions and a binuclear [Ag2(trans-4-bptzb)2](2+) subunit in which the trans-4-bptzb acts as a bidentate bridging ligand with one tetrazolyl group. In 2, the 3-bptzb acts as a tetradentate bridging ligand with the tetrazolyl and pyridyl groups linking Ag(I) ions to generate a 3D metal-organic framework (MOF), which contains charming meso-helix chains. The Keggin anions acting as bidentate inorganic ligands reside in the distorted tetragonal channels of the MOF. In compound 3, the 3-bptzb adopts versatile coordination modes linking Ag(I) ions to first construct loop connecting loop 1D chains, which are linked by {Ag[P2W18O62]}n zigzag chains to form a scarce hamburger-style 2D sheet. These adjacent sheets are further fused by 3-bptzb ligands to construct a 3D framework. The influences of isomeric bptzb ligands and POMs on the construction of Ag-bptzb subunits and the whole structures of the title compounds are discussed. The electrochemical behaviors and electrocatalytic activities of compounds 2 and 3 and their corresponding parent POMs as well as the fluorescent properties of the title compounds have been studied in detail. In addition, the photocatalytic activities of compounds 2 and 3 and their corresponding parent POMs for decomposition of methylene blue, rhodamine B, and methyl orange under UV irradiation have also been investigated.

The key role of -CH3 steric hindrance in bis(pyrazolyl) ligand on polyoxometalate-based compounds.

Through using two kinds of bis(pyrazolyl) ligands, four polyoxometalate (POM)-based compounds were hydrothermally synthesized and structurally characterized, [Ag3(Hbhpe)2(H2O)(H2PMo12O40)]·H2O (1), [Ag(H2bdpm)2(H2PW12O40)]·4H2O (2), [Ag6(H2bdpm)6(HPW(VI)8W(V)4O40)]·2H2O (2) and [Ag4(H2bdpm)4(H2P2W18O62)]·3H2O (4) (H2bhpe = 1,2-bis(1-H-pyrazolate)ethane, H2bdpm = 1,1'-bis(3,5-dimethyl-1H-pyrazolate)methane). In compound 1, the Ag-Hbhpe subunit is a 2D layer containing large penta-membered cycles and small tri-nuclear Ag(I) clusters. The Keggin anions covalently float on the large cycles. In compound 2, the Keggin anions are fused by [Ag(H2bdpm)2](+) subunits to form a 1D chain. Compound contains hexa-membered metal-organic cycles, which are further linked by Keggin anions to build a 1D chain. Adjacent chains share the Ag(I) ions to construct a 3D framework of 3. Compound 4 exhibits a wavy double-track chain structure, with the Wells-Dawson anions covalently suspended up and down this chain. The steric hindrance of -CH3 groups in H2bdpm leads to the formation of mono-nuclear Ag(I) subunits in 2 - 4. The influence of -CH3 steric hindrance in bis(pyrazolyl) ligands on the structures of 1 - 4 is discussed. The electrochemical and photocatalytic properties of the title compounds have been studied.

Assembly and properties of transition-metal coordination polymers based on semi-rigid bis-pyridyl-bis-amide ligand: effect of polycarboxylates on the dimensionality.

Seven new coordination polymers, [Co(3-bpcd)(1,3-BDC)(H(2)O)(3)]·H(2)O (1), [Co(3-bpcd)(1,2-BDC)(H(2)O)]·H(2)O (2), [Co(3)(3-bpcd)(1,2,4-BTC)(2)(H(2)O)(4)]·4H(2)O (3), [Co(3-bpcd)(NPH)]·2H(2)O (4), [Cu(3-bpcd)(1,3-BDC)] (5), [Cu(3-bpcd)(1,2-BDC)] (6), [Cu(3-bpcd)(1,3,5-HBTC)(H(2)O)](2)·2H(2)O (7) (3-bpcd = N,N'-bis(pyridin-3-yl)cyclohexane-1,4-dicarboxamide, 1,3-H(2)BDC = 1,3-benzenedicarboxylic acid, 1,2-H(2)BDC = 1,2-benzenedicarboxylic acid, 1,2,4-H(3)BTC = 1,2,4-benzenetricarboxylic acid, H(2)NPH = 3-nitrophthalic acid and 1,3,5-H(3)BTC = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized by assembling transition-metal cobalt-copper salts with semi-rigid bis-pyridyl-bis-amide ligand 3-bpcd and different aromatic polycarboxylic acids. Complex 1 exhibits a one-dimensional (1D) sinusoidal-like chain, which is further assembled into a three-dimensional (3D) supramolecular framework through hydrogen-bonding interactions. Complex possesses a 3D framework with 4-connected 6(6) topology, which contains a two-dimensional (2D) distorted asymmetric hexagonal grid. When 1,2,4-BTC is used in complex , a 3D framework with (6(3)·8(2)·10)(2)(6(5)·8)(2)(8) topology is constructed. Complex 2 possesses a 3D framework with 4-connected 6(6) topology, which contains a two-dimensional (2D) distorted asymmetric hexagonal grid. When 1,2,4-BTC is used in complex 3, a 3D framework with (6(3)·8(2)·10)(2)(6(5)·8)(2)(8) topology is constructed. Complex 4 possesses a 3D framework with 4-connected 6(6) topology, which is similar to that of 2 except for containing a 2D symmetric hexagonal grid. When Co(II) ion is replaced by Cu(II) ion, the 3D framework of complex 5 with (4·6(2))(4·6(6)·8(3)) topology based on 3-bpcd and 1,3-BDC ligands is obtained. Complex 6 shows a 2D cross network consisting of a superposed Cu-3-bpcd 1D chain and 1,2-BDC, which is further expanded into a 3D supramolecular framework by hydrogen-bonding interactions. In complex 7, 1,3,5-HBTC is employed as the auxiliary ligand, and a 3D supramolecular framework based on the undulated 2D layers is formed through π-π stacking and hydrogen-bonding interactions. Both the metal ions and polycarboxylates play important roles in the construction of the title complexes. In addition, the electrochemical behaviors and the fluorescence properties of the seven complexes have been investigated.

Assemblies of copper bis(triazole) coordination polymers using the same keggin polyoxometalate template.

Four inorganic-organic hybrid compounds, [Cu(I)(4)(bte)(4)(SiW(12)O(40))] (1), [Cu(II)(2)(bte)(4)(SiW(12)O(40))].4H(2)O (2) [bte = 1,2-bis(1,2,4-triazol-1-yl)ethane], [Cu(I)(4)(btb)(2)(SiW(12)O(40))].2H(2)O (3), and [Cu(II)(2)(btb)(4)(SiW(12)O(40))].2H(2)O (4) [btb = 1,4-bis(1,2,4-triazol-1-yl)butane], were hydrothermally synthesized through use of the same Keggin polyoxometalate as the template and tuning the molar ratio of the bis(triazole) ligand to the Cu(II) ion. The ratio of the bis(triazole) ligand to Cu(II) has a crucial influence on the structures of this series. Single-crystal X-ray diffraction analyses indicate that compound 1 is constructed by tetranuclear ring-connecting chains and polymerized [Cu(bte)](+) chains, between which SiW(12) anions are inserted to form a three-dimensional (3D) structure. Compound 2 shows a (4(4).6(2)) two-dimensional grid sheet. The discrete SiW(12) anions are sandwiched by the sheets, just like "hamburgers". Compound 3 presents channel-like [Cu(2)(btb)](2+) polymerized chains, which are further connected by SiW(12) anions to construct a 3D framework. Compound 4 exhibits a (6(6)) 3D Cu-btb framework with hexagonal channels, into which the tetradentate SiW(12) anions are incorporated. The thermal stabilities of the compounds are discussed.

Assembly of the highest connectivity Wells-Dawson polyoxometalate coordination polymer: the use of organic ligand flexibility.

Through tuning the length of flexible bis(triazole) ligands and different metal ion coordination geometries, four Wells-Dawson polyoxoanion-based hybrid compounds, [Cu 6(btp) 3(P 2W 18O 62)].3H 2O ( 1) (btp = 1,3-bis(1,2,4-triazol-1-y1)propane), [Cu 6(btb) 3((P 2W 18O 62)].2H 2O ( 2), [Cu 3(btb) 6(P 2W 18O 62)].6H 2O (btb = 1,4-bis(1,2,4-triazol-1-y1)butane) ( 3), and [Cu 3(btx) 5.5((P 2W 18O 62)].4H 2O (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane) ( 4), were synthesized and structurally characterized. In compound 1, the metal-organic motif exhibits a ladder-like chain, which is further fused by the ennead-dentate [P 2W 18O 62] (6-) anions to construct a 3D structure. In compound 2, the metal-organic motif exhibits an interesting Cu-btb grid layer, and the ennead-dentate polyoxoanions are sandwiched by two Cu-btb layers to construct a 3D structure. Compound 3 exhibits a (4 (2).6 (2).8 (2)) 3D Cu-btb framework with square and hexagonal channels arranged alternately. The hexa-dentate polyoxoanions incorporate only into the hexagonal channels. In compound 4, there exist two sets of (6 (1).10 (2)) 2(6 (1).8 (2).10 (3)) 3D Cu-btx frameworks to generate a 2-fold interpenetrated structure into which the penta-dentate polyoxoanions are inserted to construct a 3D structure. The structural analyses reveal that the length of flexible bis(triazole) ligands and metal ion coordination geometries have a synergic influence on the structures of this series. To our knowledge, they have the highest connectivity for the Wells-Dawson polyoxometalate coordination polymers to date.

Asymmetrical polar modification of a bivanadium-capped Keggin POM by multiple Cu-N coordination polymeric chains.

An unprecedented asymmetrically modified bivanadium-capped Keggin polyoxometalate (POM), {AsMo12O40(VO)[VO(H2O)]}.[Cu(4,4'-bipy)]5.H2O (1) (bipy = bipyridine), has been hydrothermally synthesized and structurally characterized by a routine technique. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a unique (3,4,6)-connected 3D framework with a (6(2).8(1))2(8(3))2(6(4).8(2))2(6(1).8(14)) topology, constructed from {AsMo12O40(VO)[VO(H2O)]}5- polyoxoanions modified by six {Cu(bipy)}n coordination polymeric chains. The asymmetrical polar coordination mode has never been found in the POM chemistry hitherto. It is also the first example of the bivanadium-capped POM as an anionic template to construct a 3D framework with the highest connection number of bicapped POMs. Additionally, by just changing the length of the organic ligand, a new compound {[AsMo12O40(VO)2][Cu(bpe)]2}.[Cu(bpe)].[H2bpe].H2O (2) (bpe = bis(4-pyridyl)ethylene), has been obtained, in which the {AsMo12O40(VO)2} sections are modified by double monotrack {Cu(bpe)}n coordination polymeric chains to form a "rail-like" 1D structure.