Systematic assembly of {LnMnIII4} appended cubanes with inorganic polyoxometalate ligands and their electrocatalytic property

•A group of heterometal-substituted compounds•{LnMn4} appended cubanes•Tetravacant polyoxometalate {SiW8O31}-based sandwich polyoxotungstate

Exploration of the reactivity of the versatile polyoxometalate precursor [β2-SiW11O39]8 − with lanthanide cations, transition-metal cations, carbonate, and morpholine, afforded a group of new appended cubanes {LnMnIII4} (Ln = HoIII, TmIII, YbIII, SmIII, GdIII, ErIII and CeIV). The appended cubanes {LnMnIII4} were encapsulated by two inorganic polyoxometalate ligands, resulting in a series of heterometallic cluster-based sandwich-type compounds: K10Na3[{LnIIIMnIII4(μ3-O)2(μ2-OH)2(H2O)(CO3)}(β-SiW8O31)2]·xH2O (Ln = HoIII, x = 24 for 1; Ln = TmIII, x = 22 for 2; Ln = YbIII, x = 21 for 3); K7Na6[{LnIIIMnIII4(μ3-O)2(μ2-OH)2(H2O)(CO3)}(β-SiW8O31)2]·xH2O (Ln = SmIII, x = 22 for 4; Ln = GdIII, x = 20 for 5; Ln = ErIII, x = 22 for 6) and K7Na5[{CeIVMnIII4(μ3-O)2(μ2-OH)2(H2O)(CO3)}(β-SiW8O31)2]·24H2O (7), which were characterized by single-crystal X-ray diffraction analyses, IR spectroscopy, and thermal gravimetric analysis. Electrocatalytic study reveals that these compounds exhibited the activity of electrocatalytic reduction of sodium nitrite.

Graphical abstractA series of Ln cations were introduced into the reaction system of [β2-SiW11O39]8 -, transition metal ions, organic ligand and CO32 − resulting in a group of {LnMnIII4} cubanes stabilized by inorganic polyoxometalate ligands.Figure optionsDownload full-size imageDownload as PowerPoint slide