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The pH Dependent Nuclearity Variation of {Mo154-x}-type Polyoxomolybdates and Tectonic Effect on Their Aggregations

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posted on 13.08.2008, 00:00 by Sayaka Shishido, Tomoji Ozeki
The pH dependence of the structures of {Mo154-x} mixed-valence oxomolybdate giant clusters were investigated by synchrotron X-ray diffraction of systematically prepared crystals containing [Mo138O410(OH)20(OH2)46]40- (1), [Mo138O410(OH)20(OH2)38]40- (2), [Mo138O406(OH)16(OH2)46]28- (3), [Mo142O400(OH)52(OH2)38]28- (4), [Mo142O432(OH2)58]40- (5), [Mo148O436(OH)15(OH2)56]27- (6), [Mo150O451(OH)5(OH2)61]35- (7), and both [Mo150O442.5(OH)11.5(OH2)64]24.5- and [Mo152O446(OH)20(OH2)54]28- (8). Crystals 1, 4, and 5 contain discrete clusters while intercluster Mo−O−Mo bonds connect the clusters into chains in crystal 7, into two-dimensional networks in crystals 2 and 3, and into a three-dimensional framework structure in crystal 6. Crystal 8 contains both discrete and linearly catenated clusters: discrete {Mo150} are located between the chains of {Mo152}. Direct correlation was observed between the nuclearity of the clusters with the pH of the mother liquor. On the other hand, the geometries of extended structures do not show apparent correlation with the pH. They turned out to be governed by the tectonics of the component clusters. The pH of the mother liquor exerts influence on the extended structure through the structures of the constituent clusters.