Syntheses, structures and electrochemical properties of a class of 1-D double chain polyoxotungstate hybrids [H2dap][Cu(dap)2]0.5[Cu(dap)2(H2O)][Ln(H2O)3(α-GeW11O39)]•3H2O

A series of novel organic-inorganic hybrid 1-D double chain germanotungstates [H(2)dap][Cu(dap)(2)](0.5)[Cu(dap)(2)(H2O)][Ln(H2O)(3)(alpha-GeW11O39)]center dot 3H(2)O [Ln = La-III (1), Pr-III (2), Nd-III (3), Sm-III (4), Eu-III (5), Tb-III (6), Er-III (7)] (dap = 1,2-diaminopropane) have been hydrothermally prepared and structurally characterized by elemental analyses, powder X-ray diffraction (PXRD), IR spectra, thermogravimetric (TG) analyses, X-ray photoelectron spectroscopy (XPS) and single-crystal X-ray diffraction. The most prominent structural feature of 1-7 is that the [Ln(H2O)(3)(alpha-GeW11O39)](5-) moieties are firstly connected with each other via the W-O-Ln-O-W bridges creating a 1-D {[Cu(dap)(2)(H2O)][Ln(H2O)(3)(alpha-GeW11O39)]}(n)(3n-) polymeric chain and then two adjacent antiparallel 1-D polymeric chains are linked together through [Cu(dap)(2)](2+) linkages giving rise to the rare organic-inorganic hybrid 1-D Cu-II-Ln(III) heterometallic double-chain architectures. To the best of our knowledge, 1-7 represent the first 1-D double-chain Cu-II-Ln(III) heterometallic germanotungstates. The variable-temperature magnetic susceptibilities of 2, 4 and 7 have been investigated. Furthermore, the solid-state electrochemical and electro-catalytic properties of 3 and 4 have been measured in 0.5 mol L-1 Na2SO4 + H2SO4 aqueous solution by entrapping them in a carbon paste electrode. 3 and 4 display apparent electro-catalytic activities for nitrite, bromate and hydrogen peroxide reduction.