Photocatalytic reduction of Ag2SO4 by the Dawson anion α-[P2W18O62]6− and tetracobalt sandwich complexes

The photocatalytic behaviours of the Dawson salt α-K6[P2W18O62] and two isomers of the tetracobalt Dawson-derived sandwich complexes, αββα-Na17[Co4(H2O)(OH)(P2W15O56)2]·51H2O·2NaCl and ααβα-Na16[Co4(H2O)2(P2W15O56)2]·51H2O (abbreviated ββ-{Co4P4W30} and αβ-{Co4P4W30}, respectively), are described and compared.The direct photochemical excitation of the polyoxometalates (POM) in the presence of propan-2-ol as electron donor leads to their reduction. With polyoxometalates as photocatalyst and propan-2-ol as sacrificial electron donor, the reduction of AgI2SO4 from aqueous solutions is observed leading to metallic Agn0 clusters and colloidal metal nanoparticles stabilized by POM.In the case of both {Co4P4W30}, TEM experiments reveal that most of the Agn particles obtained with a slight excess of Ag+ are spherical with a quite large distribution in size between 10 and 100 nm.