Controllable assembly, characterization and catalytic properties of a new Strandberg-type organophosphotungstate

Abstract

Using phenylphosphonic acid, simple tungstate and copper(II) compounds as starting materials, an organic–inorganic hybrid Strandberg-type organophosphotungstate, {[(Cu(H₂O)(μ-bipy))₂(C₆H₅PO₃)₂W₅O₁₅]}_n (bipy = 4,4′-bipyridyl) (1), was assembled successfully under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods. Compound 1 represents the first example of a transition metal complex modified organophosphotungstate cluster. In the crystal structure of compound 1, the polymeric 1-D {Cu-bipy}_n chains are interconnected by [(C₆H₅PO₃)₂W₅O₁₅]⁴⁻ (abbreviated as {(C₆H₅P)₂W₅}) units into a 3-D framework. A hollow Keggin isopolytungstate [H₂W₁₂O₄₀]⁶⁻ ({W₁₂})-Cu(II) coordination polymer, {[Cu(bipy)₂((μ-bipy)Cu(bipy))₂(H₂W₁₂O₄₀)]·12H₂O}_n (2), was obtained at different molar ratios of the starting materials and pH. The two Cu(II) coordination polymers exhibit good acid-catalytic activity for the synthesis of cyclohexanone ethylene ketal. Their fluorescence properties were studied.