Jingquan Sha

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.

pH-Dependent Assembly of Hybrids Based on Wells-Dawson POM/Ag Chemistry

Four new hybrids based on the Wells-Dawson polyoxometalate [P2W18O62](6-) (P2W18), ([Ag(bipy)]2[P2W18O62]).2[H2bipy].4H2O (1), ([Ag(bipy)]4[P2W18O62]).2[Hbipy](2), K[P2W18O62].2.5[H2bipy].2H2O (3), and [P2W18O62] 2.[H2bipy]4.[Hbipy]4 .3H2O (4), were hydrothermally synthesized and structurally characterized by routine techniques and single-crystal X-ray diffraction. Compounds 1 and 2 are isolated at lower pH values. 1 represents a 3D (4,4)-net structure with NbO topology, in which the P2W18 clusters are modified by four Ag-N coordination polymeric chains, and 2 exhibits a 3D (3,4)-net structure with the (9(2).12)(8.10(4).12)(3(2).10(2).11(2))(3.6.10(2).12(2)) topology, in which Ag-bipy layers are intercalated by the dimer of P2W18 clusters in a staggering mode, and the P2W18 clusters show the highest coordination number to date. By increasing the pH value, compounds 3 and 4 are obtained as supramolecular compounds. Their structural differences reveal that the pH value of the reaction system is the key factor influencing the structure and topology of these compounds, which can be explained by the acid-base chemistry of the molecular building units and silver chemistry.

Assembly of two new polyoxometalate-templated supramolecular compounds by utilizing a ligand with a combination of rigidness and flexibility

Two new polyoxometalate-templated compounds, (bix)[Cu(bix)]3[PW12O40]·4H2O (1), and [Cu(bix)]3[PMo12O40] (2) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were hydrothermally synthesized, and characterized by elemental analyses, IR spectroscopy, thermogravimetric analyses, and single X-ray diffraction. In compound 1, the Keggin polyanions [PW12O40]3− direct the [Cu(bix)] coordination polymeric chains to form a 3D supramolecular framework with grid-like 2D channels. By changing the polyanions into [PMo12O40]3−, compound 2 is obtained, in which the [Cu(bix)] coordination polymeric chains array around the polyanions to construct a 3D supramolecular framework with 1D hexagon-like channels. Their different structures show the template effect of the polyanions. Additionally, the cyclic voltammetry measurements indicate that the supramolecular compounds keep the redox properties of their parent polyanions.

Self-organization towards complex multi-fold meso-helices in the structures of Wells–Dawson polyoxometalate-based hybrid materials for lithium-ion batteries

We utilised the rich coordination character of Wells–Dawson polyoxometalates (POMs) to explore the higher-level helical conformation of hybrids. Herein, two compounds, [Ag26(Trz)16(OH)4][P2W18O62] (1) and Na[Ag16(Trz)9(H2O)4][P2W18O62]·H2O (2) (Trz = 1,2,3 triazole), with multi-fold meso-helices were successfully isolated. Both 1 and 2 displayed two different types of four-fold meso-helices, which are composed of POMs and organic–metal subunits. The interesting thing is that the four-fold helixes of 2 sequentially evolve into the most complex eight-fold meso-helices by sharing the building blocks. In addition, the multi-chelate patterns of Wells–Dawson POMs in 2 represent the highest coordination numbers to date, which dominates the evolution from four-fold to eight-fold meso-helices. For the first time, the Wells–Dawson POMs-based hybrids 1 and 2 have been used as anode materials in lithium-ion batteries (LIBs). The initial specific capacities of 1077 mA h g−1 for 1 and 1094 mA h g−1 for 2 were much higher than those of (NBu4)6[P2W18O62] and commercial graphite as reference anodes at a current density of 100 mA cm−2. Also, both of them showed stable performance after 100 cycles.

Hydrothermal syntheses and crystal structures of hybrid materials based on Keggin cluster modified by iron complexes

Three new organic-inorganic hybrid complexes based on the Keggin polyoxometalates (POMs) modified by transition metal iron and N-ligand organic moiety: [Fe(phen)3]2 (1) [Fe(phen)2(H2O)]2  · 2H2O (2) and [Fe(phen)3]2  · 0.5H2O (3) (phen = 1,10-phenanthroline) have been hydrothermally synthesized and structurally characterized. Crystal data for complex 1: C72H48Fe2M12N12O41PV, triclinic, , a = 11.6618(2) Å, b = 13.8523(2) Å, c = 14.9168(2) Å, α = 105.87(3)°, β = 93.103(2)°, γ = 96.609(2)°, V = 2293.2(5) Å3, Z = 1; for complex 2: C48H32Fe2PMo12N8O44, triclinic, , b = 13.357(3) Å, c = 13.701(3) Å, α = 69.09(3)°, β = 71.37(3)°, γ = 78.21(3)°, V = 1766.4(6) Å3, Z = 1; for complex 3: C72H50Fe2Mo12N12O41Ge, triclinic, , b = 13.676(3) Å, c = 14.627(3) Å, α = 105.05(3)°, β = 109.64(3)°, γ = 93.07(3) °, V = 2185.6(7) Å3, Z = 1. Other characterizations by element analysis, IR, XPS and TGA analysis are also described. Their electrochemical properties have been studied in the paper.

A novel inorganic-organic hybrid based on a Wells–Dawson polyanion containing two types of organic fragments

A new inorganic-organic hybrid, [Zn(phen)2(ppy)][{Zn(phen)2}{Zn(phen)2(H2O)}{P2W18O62}] · 2H2O (phen = 1,10′-phenanthroline, ppy = 2-(5-phenylpyridin-2-yl)pyridine) (1), by using pre-prepared Wells–Dawson salt α-K6P2W18O62 · 15H2O as precursor, has been synthesized under hydrothermal conditions. Compound 1 was characterized by single-crystal X-ray diffraction, elemental analyses, IR spectrum and cyclic voltammetry. Yellow crystals crystallized in the monoclinic space group P2 (1)/c with a = 16.2450(11) Å, b = 17.0918(11) Å, c = 43.640(3) Å, β = 92.0060(10)°, V = 12109.4(14) Å3, Z = 4. The title compound represents a novel zero-dimensional structure based on bisupporting Wells–Dawson POM: one terminal oxygen atom located in the “belt” site and another located in the “cap” site of the same hemisphere of the polyanion are coordinated by Zn2+ cations. Compound 1 also contains the isolated secondary metal complex [Zn(phen)2(ppy)]2+ with two different organic ligands phen and ppy.