Influence of N-donor sites in 5-(x-pyridyl)-1H-tetrazole ligands (x = 2, 4) on assembly of polyoxometalate-based compounds modified by multinuclear metal clusters and infinite chains

Abstract

Through tuning the N-donor site of the pyridyl group in 5-(x-pyridyl)-1H-tetrazole ligands (x = 2, 4), four new Keggin-based compounds, [Cu7(2-ptz)8(OH)2(H2O)2(HPMoVI10MoV2O40)]·4H2O (1), [Cu5(2-ptz)6(HPMoVI10MoV2O40)(H2O)4]·4H2O (2), [Ag6(4-ptz)4(H2SiMo12O40)] (3) and [Ag5(4-ptz)4(H2PMo12O40)]·5H2O (4) (2-ptzH = 5-(2-pyridyl)-1H-tetrazole, 4-ptzH = 5-(4-pyridyl)-1H-tetrazole), were successfully synthesized under hydrothermal conditions and structurally characterized. Compound 1 possesses two kinds of CuII subunits: penta-nuclear clusters and mono-nuclear subunits, which connect with each other to form a one dimensional (1D) stair-like metal–organic chain. The adjacent 1D stair-like chains are further linked by tetradentate Keggin anions to construct a 2D layer. In compound 2, the tetra-nuclear CuII clusters and mono-nuclear CuII subunits construct a 2D metal–organic layer, which is further linked by bidentate Keggin anions to build a 3D framework. In compound 3, the 4-ptz ligand links AgI ions with tetrazole groups to form 1D infinite Ag–ptz chains, which are extended by the pyridyl group of 4-ptz and the tetrazole groups of other 4-ptz molecules to construct a 2D layer. The adjacent 2D layers are further linked by 6-connected Keggin anions to build a 3D framework. In compound 4, the 4-ptz ligands are linked by AgI ions to form 1D infinite Ag–ptz belts. The Keggin anions are linked by AgI ions to construct another infinite inorganic chain, in which each Keggin anion provides six oxygen atoms to coordinate with the AgI ions from adjacent Ag–ptz belts to construct a 2D layer. The roles of the ptz ligands with different N-donor sites in the construction of multinuclear clusters and 1D chains are discussed. The electrochemical and photocatalytic properties of the title compounds were investigated as well.