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

Abstract

A series of novel organic–inorganic hybrid 1-D double chain germanotungstates [H₂dap][Cu(dap)₂]_0.5[Cu(dap)₂(H₂O)][Ln(H₂O)₃(α-GeW₁₁O₃₉)]·3H₂O [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(α-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(α-GeW₁₁O₃₉)]}_n³ⁿ⁻ 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.