Photocoloration in Hybrid Amino Acid Polyoxometalates

Abstract

The study of four different salts of a hybrid glycine–polyoxotungstate has revealed photocoloration that is dependent on the intramolecular hydrogen bonding between glycine ligand ammonium groups and the polyoxotungstate. Four compounds comprised of the hybrid polyoxometalate [As4{W3Y}W44Y4O159(Gly)8(H2O)12]9– (Gly = glycine) with glycinium, benzylammonium, 4-methylbenzylammonium, or benzyltriethylammonium countercations have been synthesized and structurally characterized. In the solid state, two of the compounds exhibit coloration associated with photoreduction, cycling from white to blue under UV irradiation, and bleaching back to white following reoxidation in air. The ability of the hyb..