Discrete Hf Metal-oxo Cluster as a Heterogeneous Nanozyme for Site-Specific Proteolysis.

The selective hydrolysis of proteins by non-enzymatic catalysis is difficult to achieve, yet it is crucial for applications in biotechnology and proteomics. Herein, we report that discrete hafnium metal-oxo cluster [Hf O (OH) (SO ) ⋅(H O) ] (Hf ), which is centred by the same hexamer motif found in many MOFs, acts as a heterogeneous catalyst for the efficient hydrolysis of horse heart myoglobin (HHM) in low buffer concentrations. Among 154 amino acids present in the sequence of HHM, strictly selective cleavage at only 6 solvent accessible aspartate residues was observed.

Reversible M-M Bonding by Alkaline Earth Metals (Mg, Ca, Sr, Ba) in Graphite Intercalation Compounds.

The alkaline earth metals (M=Mg, Ca, Sr, and Ba) exhibit a +2 oxidation state in nearly all known stable compounds, but M dimeric complexes with M-M bonding, [M (en) ] , (en=ethylenediamine) of all these metals can be stabilized within the galleries of donor-type graphite intercalation compounds (GICs). These metals can also form GICs with more conventional metal (II) ion complexes, [M(en) ] . Here, the facile interconversion between dimeric-M and monomeric-M intercalates upon the addition/removal of en are reported.

Peroxide-Promoted Disassembly Reassembly of Zr-Polyoxocations.

Zr/Hf aqueous-acid clusters are relevant to inorganic nanolithography, metal-organic frameworks (MOFs), catalysis, and nuclear fuel reprocessing, but only two topologies have been identified. The () polyoxocation is the ubiquitous square aqueous Zr/Hf-oxysalt of all halides (except fluoride), and prior-debated for perchlorate. Simply adding peroxide to a Zr oxyperchlorate solution leads to a striking modification of , yielding two structures identified by single-crystal X-ray diffraction.

Beyond Charge Balance: Counter-Cations in Polyoxometalate Chemistry.

Polyoxometalates (POMs) are molecular metal-oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self-assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered.

The role of titanium-oxo clusters in the sulfate process for TiO production.

TiO is manufactured for white pigments, solar cells, self-cleaning surfaces and devices, and other photocatalytic applications. The industrial synthesis of TiO entails: (1) the dissolution of ilmenite ore (FeTiO) in aqueous sulfuric acid which precipitates the Fe while retaining the Ti in solution, followed by (2) dilution or heating the Ti sulfate solution to precipitate the pure form of TiO. The underlying chemistry of these processing steps remains poorly understood.

Thorium Oxo-Clusters as Building Blocks for Open Frameworks.

Fundamental understanding of tetravalent actinide chemistry is essential to optimize many steps of the nuclear fuel cycle, as well as to predict actinide speciation in the environment. Herein, we report synthesis and structure of three open inorganic frameworks composed of Th -oligomers and sulfate anions. The compounds [Th O (OH) (SO ) (H O) ]⋅28 H O (1), [Th O (OH) (SO ) (H O) ]⋅ 1 TMA⋅18 H O (2), and [Th O (OH) (SO ) (H O) ]⋅2 TMA⋅n H O (3) were obtained by slow evaporation of aqueous Th -SO solutions, with variable SO :Th ratios (SO :Th =1:1, 1.

Aqueous Bismuth Titanium-Oxo Sulfate Cluster Speciation and Crystallization.

Inorganic aqueous metal-oxo clusters are both functional "molecular metal oxides" and intermediates to understand metal oxide growth from water. There has been a recent surge in discovery of aqueous Ti-oxo clusters but without extensive solution characterization. We use small-angle and total X-ray scattering, dynamic light scattering, transmission electron microscopy, and a single-crystal X-ray structure to show that heterometals such as bismuth stabilize labile Ti-oxo sulfate clusters in aqueous solution.

Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems.

Ion pairs and solubility related to ion-pairing in water influence many processes in nature and in synthesis including efficient drug delivery, contaminant transport in the environment, and self-assembly of materials in water. Ion pairs are difficult to observe spectroscopically because they generally do not persist unless extreme solution conditions are applied. Here we demonstrate two advanced techniques coupled with computational studies that quantify the persistence of ion pairs in simple solutions and offer explanations for observed solubility trends.

Closing Uranyl Polyoxometalate Capsules with Bismuth and Lead Polyoxocations.

Uranyl polyoxometalate clusters are both fundamentally fascinating and potentially relevant to nuclear energy applications. With only ten years of development, there is still much to be discovered about heterometal derivatives and aqueous speciation and behavior. Herein, we show that it is possible to encapsulate the polyoxocations [Bi O ] and [Pb O ] in [(UO )(O )(OH)] (denoted Bi@U and Pb@U ) in pure form and high yields despite the fact that under aqueous conditions, these compounds are stable on opposite ends of the pH scale.