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

Abstract The photocatalytic behaviours of the Dawson salt α-K 6 [P 2 W 18 O 62 ] and two isomers of the tetracobalt Dawson-derived sandwich complexes, αββα-Na 17 [Co 4 (H 2 O)(OH)(P 2 W 15 O 56 ) 2 ]·51H 2 O·2NaCl and ααβα-Na 16 [Co 4 (H 2 O) 2 (P 2 W 15 O 56 ) 2 ]·51H 2 O (abbreviated ββ-{Co 4 P 4 W 30 } and αβ-{Co 4 P 4 W 30 }, 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 Ag I 2 SO 4 from aqueous solutions is observed leading to metallic Ag n 0 clusters and colloidal metal nanoparticles stabilized by POM. In the case of both {Co 4 P 4 W 30 }, TEM experiments reveal that most of the Ag n particles obtained with a slight excess of Ag + are spherical with a quite large distribution in size between 10 and 100 nm.