Polyoxometalates (POMs) are discrete clusters of redox-active metal oxides, many of which can be linked to organic moieties. Here, we show how it is possible to link Mn Anderson POMs to terminal alkyne and azide groups and develop appropriate conditions for their Cu-catalyzed alkyne-azide cycloaddition (or "click" reaction). These coupling reactions are then used to link the clusters together, forming monodisperse linear Mn Anderson oligomers, here with examples ranging in size from two to five clusters. These oligomers are built up sequentially using a combination of mono- and difunctionalized clusters, giving an unprecedented level of control over the size and structure of the resulting hybrid POMs. This new synthetic methodology therefore opens the way for the synthesis of metal oxide hybrid oligomers and polymers by coupling control, minimizing side products, producing nanosized molecular hybrid organic-inorganic oxides ca. 4-9 nm in size, with molecular weights ranging 2-10 kDa.

The design of highly flexible framework materials requires organic linkers, whereas inorganic materials are more robust but inflexible. Here, by using linkable inorganic rings made up of tungsten oxide (P8W48O184) building blocks, we synthesized an inorganic single crystal material that can undergo at least eight different crystal-to-crystal transformations, with gigantic crystal volume contraction and expansion changes ranging from −2,170 to +1,720 Å3 with no reduction in crystallinity. Not only does this material undergo the largest single crystal-to-single crystal volume transformation thus far reported (to the best of our knowledge), the system also shows conformational flexibility while maintaining robustness over several cycles in the reversible uptake and release of guest molecules switching the crystal between different metamorphic states. This material combines the robustness of inorganic materials with the flexibility of organic frameworks, thereby challenging the notion that flexible materials with robustness are mutually exclusive.

Here we report a suite of approaches for the isolation of asymmetrically grafted organic-inorganic hybrid Mn-Anderson polyoxometalate compounds (TBA) 3 [MnMo 6 O 18 ((OCH 2) 3 CNHR 1)((OCH 2) 3 CNHR 2)] (where TBA ¼ tetrabutylammonium). Both a "pre-functionalization" route (for compound 1-R 1 ¼-COC 14 H 9 , R 2 ¼-H) using two different TRIS-based ligands ((HOCH 2) 3 CNHR), and a "post-functionalization" of the preformed TRIS Mn-Anderson compound (R 1 ¼ R 2 ¼-H) were demonstrated. Compounds 2 (R 1 ¼-COC 15 H 31 , R 2 ¼-CO(CH 2) 2 COOH) and 3 (R 1 ¼-COC 15 H 31 , R 2 ¼-H) are some of the first reported examples of asymmetric Mn-Anderson compounds to have been synthesized by the latter route. The reliable and broadly applicable chromatographic method used to isolate these compounds relies on the difference in affinity of compounds' organic moieties for reverse phase (RP) media; the target asymmetric cluster will have an intermediate affinity, between that of the two symmetric by-products. For instances where this is not the case, we have prepared and isolated a "universal" asymmetric Mn-Anderson precursor 4 (R 1 ¼-C(O)OC 14 H 11 , R 2 ¼-H), which can be used as a precursor to synthesize practically any asymmetric Mn-Anderson system. The use of 4 as an "universal" precursor was successfully demonstrated in the synthesis and isolation of compound 5 (R 1 ¼-COC 2 H 5 , R 2 ¼-H), which would not be accessible by a simple 'one pot' approach. In addition to removing a significant barrier to the exploitation of asymmetric Mn-Anderson clusters as new functional materials, the methods presented here should be applicable to a range of other hybrid organic-inorganic clusters.

A polyoxometalate-based molecular triangle has been synthesized through the metal-driven self-assembly of covalent organic/inorganic hybrid oxo-clusters with remote pyridyl binding sites. The new metallomacrocycle was unambiguously characterized by using a combination of (1)H NMR spectroscopy, 2D diffusion NMR spectroscopy (DOSY), electrospray ionization travelling wave ion mobility mass spectrometry (ESI-TWIM-MS), small-angle X-ray scattering (SAXS) and molecular modelling. The collision cross-sections obtained from TWIM-MS and the hydrodynamic radii derived from DOSY are in good agreement with the geometry-optimized structures obtained by using theoretical calculations. Furthermore, SAXS was successfully employed and proved to be a powerful technique for characterizing such large supramolecular assemblies.

The process of converting structural models derived from single-crystal X-ray diffraction experiments into physical models for the purposes of visualization/communication and collaboration by the use of three-dimensional (3D) printing techniques is described. Digital information regarding the relative positioning of atoms in a crystal structure is translated, using a suite of computer programs, into a 3D computer model of a solid form, corresponding to that information which can then be saved in a file format for 3D printing. These files are then used to produce to-scale physical models of the structural information using two different 3D printing methodologies.