Bi-antimony capped Keggin polyoxometalate modified with Cu-ligand fragment

Three polyoxometalates consisting of bi-antimony capped Keggin-type clusters: [Cu(mbpy)2]2[PMo12O40Sb2]·4H2O (1), [Cu(mbpy)2][PMo12O40Sb2] (2) and {Cu(mbpy)[Cu(mbpy)2]2}[VMo8V4O40Sb2]·2H2O (3) (mbpy=4,4′-dimethyl–2,2′- dipyridyl in 1 and 2; 5,5′-dimethyl–2,2′-dipyridyl in 3) have been synthesized and characterized by IR, X-ray powder diffraction, TG analysis and electrochemical property. Single-crystal analysis revealed that all of three compounds are built upon bi-antimony capped Keggin-type polyoxoanions and Cu-mbpy cations. In 1–3, two SbIII centers located at the two opposite of anionic surface adopt fundamentally tetragonal pyramidal coordination geometry. Both compounds 1 and 2 consist of P-centered Keggin structure, while compound 3 presents a V-centered Keggin anion. The Keggin-type anions present different structural features: isolated cluster in 1 and Cu-ligand-supported cluster in 2 and 3.