Assembly of inorganic [Mo2S2O2]2+ panels connected by selenite anions to nanoscale chalcogenide-polyoxometalate clusters

Abstract

We describe how supramolecular assembly, mediated by control of the ratio of the hetero-Atoms in the units [Mo2S2O2]2+ and SeO32- leads to the formation of new types of building blocks, [(Mo2O2S2)3(OH)4(H2O)6(SeO3)] = {Mo6} and [(Mo2O2S2)2(OH)2(H2O)4(SeO3)] = {Mo4} which are linked in an type of inorganic 'panelling' to the assembly of a range of new clusters 1-3 with the general formula {(Mo2O2S2)x(OH)y(SeO3)z(H2O)w}n-, where x, y, z, w, n = [8, 0, 20, 8, 24] for 1, [14, 14, 17, 8, 20] for 2 and [8, 8, 8, 0, 8] for 3. Cluster 1, a rare example of inorganic cryptand, exhibits an elliptical "endo" motif defining an anisotropic ellipse with the dimensions 1.7 × 1.0 nm, with pores ranging from 5.3 to 6.4 Å and site selective cation recognition properties; cluster 2 exhibits an "exo" structural motif constructed by 3 × {Mo6} and 2 × {Mo4} panels spanning a cross shape 2.4 × 2.0 nm and cluster 3 a ring shaped structure of a 1.5 nm in diameter. The control of endo vs. exo topology as a function of the Se:Mo ratio is reflected to the difference in surface area of ca. 500 Å2 between clusters 1 and 2 intermolecular interactions and proton conduction properties, and this work shows that very simple synthetic parameters can critically change the structure and properties of all-inorganic nanoscale chalcogenide-polyoxometalates.