Building block approach to a series of substituted Keggin-type inorganic–organic hybrids

Abstract

A series of polyoxotungstates based on monovacant Keggin-type anions have been synthesized via a step-by-step assembly process. Reaction of trivacant Keggin-type polyoxotungstate precursors with cupric sulfate at pH ≈ 5 in the presence of 1,2-ethylenediamine (abbreviated as en) led to the isolation of a inorganic–organic hybrid compound, [Cu(en) 2][Cu(en) 2H 2O] 2[SiW 11CuO 39]·5H 2O ( 1). Compound 1 exhibits a 1D chain structure constructed from mono-copper-substituted Keggin silicotungstate grafted by {Cu(en) 2} groups. When lanthanide ions were introduced into the present system, H 14[Cu(en) 2] 4[Ce(PW 11O 39) 2] 2·2en·21H 2O ( 2), H 14[Cu(en) 2] 4[Pr(PW 11O 39) 2] 2·11H 2O ( 3) and H 8[Cu(en) 2H 2O] 4[Cu(en) 2]{[Cu(en) 2][Pr(PW 11O 39) 2]} 2·2en·12H 2O ( 4) have been successfully synthesized, which all show 1D chain structures constructed from {Ln(PW 11O 39) 2} and {Cu(en) 2} moieties. Magnetic study of 1 reveals weak ferromagnetic interactions exist in it. The cyclic voltammetry behaviors of compounds 2– 4 have also been investigated.