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

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)2H2O]2[SiW11CuO39]·5H2O (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, H14[Cu(en)2]4[Ce(PW11O39)2]2·2en·21H2O (2), H14[Cu(en)2]4[Pr(PW11O39)2]2·11H2O (3) and H8[Cu(en)2H2O]4[Cu(en)2]{[Cu(en)2][Pr(PW11O39)2]}2·2en·12H2O (4) have been successfully synthesized, which all show 1D chain structures constructed from {Ln(PW11O39)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.

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