Xiao-g Lin

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.

Tuning the oxidation states of copper ions (+I/+II) to construct different Keggin-based topology structures

Through tuning the oxidation states of CuI/II, two Keggin-based compounds with different topologies, [ (btx)4(P O40)] (1) and [ (btx)4(SiW12O40)] (2) (btx = 1,6-bis(1,2,4-triazol-1-y1)hexane), were synthesized and structurally characterized. In 1, there exist decanuclear CuI circuits, which are linked through N1-containing btx ligands to construct a grid-like 2-D layer. Three sets of these layers interpenetrate to build a three-fold interpenetrating framework. The Keggin polyanions connect the adjacent three-fold interpenetrating frameworks to construct a 3-D structure. In 2, the CuII-btx moiety shows a (66) 3-D hexagonal channel-style framework. The Keggin polyanion offering four terminal oxygen atoms incorporates with this metal–organic framework imbedding the channels. The different oxidation states of copper ions (+I/+II) induces distinct coordination modes of btx and Keggin polyanions and affects the whole structural topologies. Tuning the oxidation states of copper ions is an effective strategy for obtaining POM-based topologies. In addition, the electrochemical properties of 1 and 2 bulk-modified carbon-paste electrodes are reported.

Hydroxyl- and chloro-bridges as “structural assistants” in the construction of two new Keggin-based 3D frameworks

Two new Keggin-based three dimensional (3D) frameworks, [CuI4(btb)2(μ-OH)(PW12O40)] (1) and [CuII2(btb)4(μ-Cl)(PW12O40)]·3H2O (2) (btb = 1,4-bis(1,2,4-triazol-1-y1)butane), were synthesized and structurally characterized. In compound 1, the metal–organic subunit is a wave-like 2D layer consisting of ellipse-shaped tetra-nuclear CuI cycles. Furthermore, these layers are bridged by hydroxyl groups through Cu–(OH)–Cu bonds, resulting in the construction of a 3D porous metal–organic framework (MOF). The Keggin anions, acting as inorganic templates, are embedded in the channels of the structure. In compound 2, a 2D CuII–btb layer exists that incorporates quadrangular tetra-nuclear CuII cycles. The two adjacent layers covalently capture the Keggin anions between them to construct a hamburger-like subunit. Furthermore, these subunits are linked by chloro-bridges (Cu–Cl–Cu), which build a 3D framework with channels. The big voids in the channels led to a two-fold interpenetrating structure for compound 2. Additionally, the photocatalytic properties and electrochemical behavior of compounds 1 and 2 have been investigated.

A new organopolymolybdate polymer for linking metal-organic moiety through Mo–N bonds

A new organopolymolybdate polymer, [Zn2(H2biim)4(Hbiim)2][H2(γ-Mo8O26)]·8H2O (1) (H2biim = 2,2′–biimidazole), was synthesized under hydrothermal conditions. In 1, H2biim has chelate and linking roles. Three H2biim chelate one Zn to form a cationic metal-organic subunit; two subunits link one octamolybdate through Mo–N bonds, forming a two-supporting anion. There are abundant π…π stacking interactions between these anions inducing a 1-D supramolecular chain. The electrochemical behavior and photoluminescence of 1 have been studied.

Two new 1-D and 3-D Wells–Dawson structures assisted by alkali metals

Two new Wells–Dawson based compounds containing alkali metals, [Ag(H2biim)2]2·[Ag5(H2biim)10Na2(H2O)2(H3/2P2W18O62)2]·12H2O (1) and [Cd(H2biim)2 K(P2W18O62)1/2] (2) (H2biim = 2,2′-biimidazole), have been synthesized under hydrothermal conditions. In 1, two-supporting Wells–Dawson anions are linked by a [Ag(H2biim)2]+ subunit to form a dimer. The adjacent dimers are further connected by Na+ through (POM)O-Na-O(POM) bonds to build a 1-D chain. In 2, adjacent anions are linked by two [Cd2(H2biim)2]4+ subunits and a 1-D chain is formed. Furthermore, the anion in the chain is fused by six K+ ions and a 3-D framework is obtained. The alkali metals exhibit crucial influence on the conversion of dimensionality assisting anions and Ag-H2biim subunits to construct 1-D and 3-D frameworks. The electrochemical and photocatalytic properties of 1 and 2 have been investigated. Graphical Abstract