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

Abstract

Two new isopolytungstate compounds, namely [Cu₄(2,2′-bipy)₄(H₂O)₂(W₆O₂₂)]·4H₂O (1) and [Cu(en)₂Na₈(H₂O)₂₈(H₂W₁₂O₄₂)]·4H₂O (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 [Na₃(H₂O)₁₀]³⁺ and [Na₂(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.