Five compounds based on [TeMo6O24]6− and [β-Mo8O26]4− anions synthesized by using different symmetrical and asymmetric N-donor ligands

Abstract

Five polyoxometalate-based compounds were synthesized under hydrothermal conditions, namely [Cu₃(OH)₄(Ptla)₂(H₄TeMo₆O₂₄)]·3H₂O (1), [Cu₂(talm)₂(H₆TeMo₆O₂₄)]·6H₂O (2), {Cu₂(OH)(Ptep)₂[H(β-Mo₈O₂₆)]}·2H₂O (3), [Cu(bimeb)(H₂O)₂][(β-Mo₈O₂₆)_0.5] (4), and [Cu₅(OH)₂(Ptpi)₂(H₂O)₆][H₄(TeMo₆O₂₄)₂] (5) (Ptla = 2-(3-pyridin-4-yl-[1,2,4]triazol-4-yl)-ethylamine, talm = Tris(2-aminoethyl)amine, Ptep = 1-[2-(3-pyridin-4-yl-[1,2,4]triazol-4-yl)-ethyl]-piperazine, bimeb = 3,5-bis(imidazol-1-yl)methylbenzene, Ptpi = 1-[2-(3-pyridin-4-yl-[1,2,4]triazol-4-yl)-propyl]-imidazol). Compounds 1, 2 and 5 are all based on Anderson anions. In compound 1, the trinuclear Cu clusters link anions to form a 2D layer. Adjacent layers are further connected by Ptla ligands to construct a 3D framework. Compound 2 exhibits a 2D grid layer with [TeMo₆O₂₄]⁶⁻ anions linked by [Cu(talm)]²⁺ subunits. Both triazol and pyridine groups of Ptpi coordinate with Cu atoms, inducing the 3D framework of 5. Compounds 3 and 4 are based on β-Mo₈ anions. In compound 3, the Ptep ligands are linked by Cu atoms to build a cycle-connecting-cycle chain and the β-Mo₈ anions are discrete. In compound 4, the Cu atoms connect infinite [Cu(bimeb)]_nⁿ⁺ chains to form a 3D structure. These five compounds can be used as amperometric detectors to detect NO₂⁻ and H₂O₂, especially 3 and 4 which can detect the cation Cr(VI). Additionally, the title compounds possess excellent photocatalytic activity, which can not only photocatalytically degrade organic dyes, but also can photocatalytically reduce Cr(VI) especially compounds 3 and 4.