The pH Dependent Nuclearity Variation of {Mo_154-<i>x</i>}-type Polyoxomolybdates and Tectonic Effect on Their Aggregations

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.本研究通过对系统制备的含下述阴离子团簇的晶体开展同步辐射X射线衍射（synchrotron X-ray diffraction）分析，探究了{Mo154-x}混合价氧钼酸盐巨型团簇（mixed-valence oxomolybdate giant clusters）的结构随pH值的变化规律：[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)，以及同时包含[Mo150O442.5(OH)11.5(OH2)64]24.5-与[Mo152O446(OH)20(OH2)54]28-的晶体(8)。晶体1、4与5仅含分立团簇；晶体7中，团簇间Mo-O-Mo键将团簇连接为一维链状结构；晶体2与3中团簇组装为二维网状结构；晶体6中团簇形成三维骨架结构。晶体8同时存在分立团簇与线性串接团簇：分立的{Mo150}团簇位于{Mo152}链之间。研究发现团簇的核数与母液pH值存在直接关联。另一方面，延伸结构的几何构型与pH值无明显相关性，其组装模式由组成团簇的构筑特性所决定。母液pH值通过调控组成团簇的结构，进而调控延伸结构。