Two isopolytungstate compounds based on rare [W6O22]8- and [H2W12O42]10- fragments captured by premade copper(II) complexes

Two new isopolytungstate compounds, namely [Cu-4(2,2-bipy)(4)(H2O)(2)(W6O22)]4H(2)O (1) and [Cu(en)(2)Na-8(H2O)(28)(H2W12O42)]4H(2)O (2) (2,2-bipy = 2,2-bipyridine, en = 1,2-ethylenediamine), were synthesized under hydrothermal conditions and in aqueous solution, respectively, and characterized by single-crystal X-ray diffraction, elemental analyses and FT-IR spectra. In compound 1, there is a rare hexatungstate anion [W6O22](8-), which is firstly captured by copper(ii) complexes under hydrothermal condition by using sodium tungstate. The [W6O22](8-) cluster is covered by two [Cu(2,2-bipy)](2+) and two [Cu(H2O)(2,2-bipy)](2+) clusters to form a tetra-supporting anion. In compound 2, the paradodecatungstate anion [H2W12O42](10-) was captured by [Cu(en)(2)](2+) clusters in aqueous solution. The [H2W12O42](10-) anions are linked by [Na-3(H2O)(10)](3+) and [Na-2(H2O)(8)](2+) clusters to construct an inorganic layer. The [Cu(en)(2)](2+) clusters connect these inorganic layers to build a 3D framework of 2. We studied the electrochemical and photocatalytic properties of these compounds.