A new series of polyoxometalate compounds built up of paradodecatungstate anions and transition metal/alkaline-earth metal cations

Three new extended frameworks based on the paradodecatungstate cluster and transition metals or alkaline-earth metal have been synthesized and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis (TGA), X-ray powder diffraction (XRPD) and single crystal X-ray diffraction. The 2D layered structure of the compound [Na8(H2O)28][Mn(H2O)2(H2W12O42)]·4H2O (1) is formed by the interconnection of 1D [Mn(H2O)2(H2W12O42)]n8− and [Na8(H2O)28]n8+ chains. In the compound [Zn5(H2O)20(H2W12O42)]·16H2O (2), two neighboring paratungstate ions [H2W12O42)]10− are linked by [Zn4(H2O)14]8+ units, leading to the formation of a 2D layer containing rhombic channels. The anion [Sr2(H2O)6(H2W12O42)]6− of the compound K[Na5(H2O)6][Sr2(H2O)6(H2W12O42)]·18H2O (3) shows a layer-like structure in which paratungstate-B units act as six-dentate ligands coordinating to six Sr2+ ions through the terminal oxygen atoms. Interestingly, the strong involvement of the potassium and sodium counteractions leads the neighboring layers to tie together generating a 3D network containing two types of channels. Furthermore, compounds 1–3 give intense blue luminescent emissions in solid state and the magnetic susceptibility of compound 1 has also been studied.

Graphical abstractThree new polyoxometalate compounds based on the paradodecatungstate cluster and transition metals or alkaline-earth metal, [Na8(H2O)28][Mn(H2O)2(H2W12O42)]·4H2O (1), [Zn5(H2O)20(H2W12O42)]·16H2O (2), and K[Na5(H2O)6][Sr2(H2O)6(H2W12O42)]·18H2O (3) have been synthesized and characterized, in which paradodecatungstate clusters serve as two-, eight-, and six-dentate ligands, respectively, linking secondary metal ions into high-dimensional frameworks containing channels. This work provides new possibilities for the design of high-dimensional covalent solid materials.Figure optionsDownload full-size imageDownload as PowerPoint slide