Multi-Iron Tungstodiarsenates. Synthesis, Characterization, and Electrocatalytic Studies of αββα-(Fe III OH 2 ) 2 Fe III 2 (As 2 W 15 O 56 ) 2 12 -
2003; American Chemical Society; Volume: 42; Issue: 4 Linguagem: Inglês
10.1021/ic0261169
ISSN1520-510X
AutoresIsraël M. Mbomekallé, Bineta Keita, Louis Nadjo, P. Berthet, Kenneth I. Hardcastle, Craig L. Hill, Travis M. Anderson,
Tópico(s)Nanocluster Synthesis and Applications
ResumoReaction of the trivacant lacunary complex, α-Na12[As2W15O56], with an aqueous solution of Fe(NO3)3·9H2O yields the sandwich-type polyoxometalate, αββα-Na12(FeIIIOH2)2FeIII2(As2W15O56)2 (Na1). The structure of this complex, determined by single-crystal X-ray crystallography (a = 13.434(1) Å, b = 13.763(1) Å, c = 22.999(2) Å, α = 90.246(2)°, β = 102.887(2)°, γ = 116.972(1)°, triclinic, P1̄, R1 = 5.5%, based on 25342 independent reflections), consists of an FeIII4 unit sandwiched between two trivacant α-As2W15O5612- moieties. UV−vis, infrared, cyclic voltammetry, and elemental analysis data are all consistent with the structure determined from X-ray analysis. Magnetization studies confirm that the four Fe(III) centers are antiferromagnetically coupled. A cyclic voltammogram of Na1 reveals that a three-wave W(VI) system replaces the two-wave W(VI) system found in the precursor α-As2W15O5612- complex. The observed modifications in the CV patterns of Na1 and α-As2W15O5612- are most likely due to subsequent changes in the acid−base properties of two reduced POMs that occur as a result of Fe(III) incorporation. Na1 is shown to be more efficient than the monosubstituted complex α2-As2(FeIIIOH2)W17O617- in the electrocatalytic reduction of dioxygen. This is attributed to cooperativity effects among the adjacent Fe(III) centers in Na1.
Referência(s)