Two novel sandwiched-type polyoxotungstates containing Zn6 transition-metal cluster: Syntheses, structures and luminescent property

Two novel Zn6 sandwiched polyoxometalates, [Zn(phen)2]2[Zn6(phen)2(AsW9O33)2] (1) and K11H2Zn[(ZnCl)6(AsW9O33)2]Cl · 27H2O (2), have been synthesized and characterized by X-ray single-crystal analysis, IR, and fluorescence spectrum. The polyoxoanions in both compounds can be characterized as two {AsIIIW9O33}9− moieties linked through Zn6 transition-metal cluster to form the sandwich-type polyoxotungstates. In compound 1, six Zn atoms in the equatorial part of the polyoxoanions have two different coordination environments: four Zn sites exhibit distorted octahedral geometry, and the other two Zn atoms show square pyramidal geometry. In the polyoxoanion of compound 2, all Zn atoms are square pyramidal geometry, and held together to form a hexagonal metallocycle by edge-sharing oxygen atoms. In this Zn6 cluster, the shortest distance of neighboring Zn⋯Zn is 3.147(1) Å. In addition, compound 2 exhibits purple photoluminescence at room temperature.