Ross S. Winter

A Mixed‐Valence Manganese Cubane Trapped by Inequivalent Trilacunary Polyoxometalate Ligands

The title compound contains an embedded mixed-valence {Mn5O6} cubane core, which is structurally similar to the active site in photosystem II. Solid-, solution-, and gas-phase studies indicate the presence of three lacunary Keggin fragments, thereby giving insight into the complex solution chemistry of plenary POM fragments.

Modular Redox‐Active Inorganic Chemical Cells: iCHELLs

Interfacial membrane formation by cation exchange of polyoxometalates produces modular inorganic chemical cells with tunable morphology, properties, and composition (see picture). These inorganic chemical cells (iCHELLs), which show redox activity, chirality, as well as selective permeability towards small molecules, can be nested within one another, potentially allowing stepwise reactions to occur in sequence within the cell.

Investigating the Transformations of Polyoxoanions Using Mass Spectrometry and Molecular Dynamics

The reactions of [γ-SiW10O36]8– represent one of the most important synthetic gateways into a vast array of polyoxotungstate chemistry. Herein, we set about exploring the transformation of the lacunary polyoxoanion [β2-SiW11O39]8– into [γ-SiW10O36]8– using high-resolution electrospray mass spectrometry, density functional theory, and molecular dynamics. We show that the reaction proceeds through an unexpected {SiW9} precursor capable of undertaking a direct β → γ isomerization via a rotational transformation. The remarkably low-energy transition state of this transformation could be identified through theoretical calculations. Moreover, we explore the significant role of the countercations for the first time in such studies. This combination of experimental and the theoretical studies can now be used to understand the complex chemical transformations of oxoanions, leading to the design of reactivity by structural control.

Synthesis and Characterization of a Series of [M2(β-SiW8O31)2]n− Clusters and Mechanistic Insight into the Reorganization of {β-SiW8O31} into {α-SiW9O34}

Lacunary polyoxometalates of low nuclearity are difficult to synthesize in isolation. We report the facile synthesis of six {M2(B-β-SiW8O31)2} clusters (M = Co/Mn/Ni/Zn/Cu(2+), Fe(3+)) that can be employed as building blocks for the formation of larger architectures. We show for the first time that such {B-β-SiW8O31} lacunae are capable of reorganizing into larger Keggin lacunary species even in the absence of an external source of tungstate. We hypothesize, based on electrospray ionization mass spectrometry evidence obtained, not only that such a transformation is only possible via an initial decomposition of the {SiW8} precursor into a {SiW6}-based intermediate but also that it is this {SiW6} species that acts as the template for the growth of the larger fragments.

A metamorphic inorganic framework that can be switched between eight single-crystalline states.

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.

Redox tuning the Weakley-type polyoxometalate archetype for the oxygen evolution reaction

Water oxidation is a key reaction for the conversion of solar energy into chemical fuels, but effective water-oxidation catalysts are often based on rare and costly precious metals such as Pt, Ir or Ru. Developing strategies based on earth-abundant metals is important to explore critical aspects of this reaction, and to see whether different and more efficient applications are possible for energy systems. Herein, we present an approach to tuning a redox-active electrocatalyst based on the doping of molybdenum into the tungsten framework of [Co4(H2O)2(PW9O34)2]10–, known as the Weakley sandwich. The Mo-doped framework was confirmed by X-ray crystallography, electrospray ionization mass spectrometry and inductively coupled plasma optical emission spectrometry studies. The doping of molybdenum into the robust Weakley sandwich framework leads to the oxidation of water at a low onset potential, and with no catalyst degradation, whereby the overpotential of the oxygen evolution reaction is lowered by 188 mV compared with the pure tungsten framework.For practical applications, water-oxidation catalysts should be inexpensive, active and stable. Here, Cronin and co-workers dope molybdenum into the Weakley sandwich-type polyoxometalate, showing that this dramatically lowers the overpotential for the oxygen evolution reaction while maintaining the stability against oxidation.