Building Block Libraries and Structural Considerations in the Self-assembly of Polyoxometalate and Polyoxothiometalate Systems

Abstract

Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems.

Thiacalixarene-Supported MoNa Clusters: Crystal Transition and Mo-S Coordination on Visible-Light Absorption

“…It is worth noting that an appealing feature of these four molecular architectures is the connectivity of the Mo ion and S atom. To the best of our knowledge, the reported oxothiomolybdate clusters typically consist of bridging S in a {Mo 2 S x } ( x = 1, 2) unit S. − If the two Mo centers and two bridging atoms are considered to be a plane, the inorganic S always displays a bridging coordination mode in the Mo 2 unit in the literature (Figure a). , In contrast, these calixarene-supported molybdenum-based molecular assemblies are associated within plane Mo–S bonds in Mo 8 Na 6 and Mo 4 Na 4 architectures (Figure b) and vertical Mo–S bonds of the plane in Mo 8 Na 8 α and Mo 8 Na 8 β clusters (Figure c), both of which have not been structurally determined. The characteristics of Mo–S bond lengths observed for these four clusters are summarized as follows: Mo–S bond lengths in Mo 8 Na 6 are 2.559–2.579 Å; Mo–S bond lengths of Mo 4 Na 4 vary from 2.570 to 2.585 Å; the distances of the Mo center and S atom in Mo 8 Na 8 α are found to be 2.716–2.771 Å; while the Mo–S distances of Mo 8 Na 8 β span the range 2.723 and 2.764 Å.…”

“…Mo-S coordination in {Mo 2 S x } unit: (a) Bridging coordination mode of S in Mo 2 serials in the literature. , (b, c) Two Mo-S coordination modes for calixarene-functionalized Mo 2 unit. Up: in Mo 8 Na 6 and Mo 4 Na 4 ; Down: in Mo 8 Na 8 α and Mo 8 Na 8 β .…”

“…41 No Mo-S coordination has been observed between Mo and calixarene ligands for both cases. Comparing large achievements in inorganic S modified polyoxometalate, 42 S from organic ligands, e.g., S from thiacalixarene ligands, coordinating to Mo has not been well exploited. 38,39,42 We envisaged that thiacalix [4]arene would be a promising ligand for the construction of novel molybdenumbased architectures through the Mo-S coordination, and the achievement of outstanding properties could be possible.…”