Zheyu Zhang

Assembly of copper–tetrazole frameworks with role-changeable Keggin clusters: syntheses, structures, solvent-dependent luminescence and electrochemistry properties

Two new Keggin-based hybrids with polynuclear Cu(I) clusters, formulated as [Cu4(HL)4(SiW12O40)]·6H2O (1) and [Cu6.5(HL)2(L)4(H2O)(H1.5SiW12O40)]·3H2O (2) (HL = 5-(4-imidazol-1-ylphenyl)-2H-tetrazole), have been hydrothermally synthesized and characterized by routine techniques. In 1, Keggin polyanions [SiW12O40]4− (SiW12) link adjacent [Cu4(HL)4]n chains to generate a 2D network. In 2, a cationic (2,3,11)-connected 3D framework, {Cu6.5(HL)2(L)4(H2O)}2.5+, is induced by SiW12 as the template. The differences in the structures of compounds 1 and 2 indicate that pH and the acid radical ions in the initial reaction system play a key role in determining the final structures. Interestingly, the ligand HL in 1 only adopts a μ1,2,3 bridging mode, while in 2, the ligand is in HL/L states and exhibits four different bridging modes: μ1,2,3,4,5, μ1,2,3,5, μ1,2,4,5, and μ1,2,4. The luminescent properties of compounds 1 and 2 have also been investigated. The results show that solvent-dependent luminescence properties can be found in 1. In addition, electrochemistry properties of 1 and 2 have also been studied.

Assembly of multinuclear Ag complexes and Keggin polyoxometalates adjusted by organic ligands: syntheses, structures and luminescence

Two unusual α-Keggin-based compounds with multinuclear silver clusters, {[Ag7(H2biim)5][PW11O39]}·Cl·H3O (1) and {[Ag2(H2biim)2][Ag(phnz)](PW12O40)}·H2O (2) (H2biim = 2,2′-biimidazole, phnz = phenazine), have been hydrothermally synthesized and structurally characterized by elemental analyses, IR spectra, thermogravimetric analysis and X-ray crystallography. Compound 1 displays a 2D network featuring dimerized monolacunary Keggin anions {PW11O39}2 which are connected together through pentanuclear silver clusters. Interestingly, besides {Ag5}5+ clusters, there are another kinds of argentophilic {Ag4}4+ clusters coexisting in compound 1. Compound 2 consists of four subunits: 1D cationic chains [Ag(phnz)]+, dinuclear silver-H2biim units [Ag2(H2biim)2]2+, discrete polyanions {PW12O40}3− and water molecules, which are further joined by hydrogen bonds to form a 3D supramolecular structure. The differences in the structures of compounds 1 and 2 indicate that the introduction of the secondary organic ligand plays a key role in determining the final structure. The electrochemical, electrocatalytic behaviors and luminescent properties of compounds 1 and 2 have also been investigated.

Assembly of hybrids based on polyoxotungstates and Co-tris(imidazolyl) complexes with bifunctional electrocatalytic activities

Three new organic–inorganic hybrid compounds based on the Keggin polyoxometalates, [Co2(tib)2(H2O)4(α-HBW12O40)]·6H2O (1), [Co2(tib)2(H2O)4(α-SiW12O40)]·4H2O (2) and [Co(H2tib)4(α-BW12O40)2]·8H2O (3) (tib = 1,3,5-tris(1-imidazoly)benzene), were hydrothermally synthesized by utilizing a pH-dependent approach in the same POM/Co/tib reaction systems. X-ray structural analyses reveal that isostructural compounds 1 and 2, obtained at pH 3.6, have a (3,4)-connected 2D net with the (42 6)(42 63 8) topology; compound 3, isolated at pH 4.8, is a “butterfly-like” structure stemming from α-BW12 polyoxoanions and Co–tib motifs. In addition, the electrocatalytic properties of compounds 1–3 were studied by cyclic voltammetry. Compounds 1–3 displayed bifunctional electrocatalytic activities toward reduction of nitrite and oxidation of ascorbic acid.

A series of hybrids with a framework constructed from {–SiW11–Ln–SiW11–}n chains and {Cu/bimpy} ribbons

This paper reports the preparation and X-ray single crystal structures of five organic–inorganic hybrid compounds with 3D framework, [Cu2.5(bimpy)2(H2O)2][Ln(H2O)3(α-SiW11O39)]·xH2O [Ln = EuIII and x = 3.5 for (1), Ln = SmIII and x = 2.5 for (2), Ln = HoIII and x = 3.5 for (3), Ln = YIII and x = 3.5 for (4), Ln = CeIII and x = 3 for (5)] (bimpy = 3,5-bis(1-imidazolyl)pyridine). Compounds 1–5 are isostructural, showing a 3D framework featured by {–SiW11–Ln–SiW11–}n inorganic chains and {Cu/bimpy} metal–organic ribbons stemmed from Cu2+ ions and bimpy ligands. The adjacent {Cu/bimpy} ribbons are connected by two antiparallel {–SiW11–Eu–SiW11–}n chains to create a 2D layer structure, which is extended to a (3,4,4,4,6)-connected 3D framework with (4·72)(4·6·73·8)(42·53·7)(42·72·92)(42·52·67·83·10) topology through the Cu–O covalent bonds. The magnetic and electrochemical properties of compounds 1 and 2 have been studied.