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.

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.

Encapsulation of a {Cu} cluster containing four [CuO] cubanes within an isopolyoxometalate {W} cluster.

We report a {Cu} embedded within a {W} cluster containing four cubane-like [CuO] units within an isopolyoxotungstate (isoPOT) in a {NaCu[(HWO) (CHCOO)(OH)]}·88HO (1) and a polyanion Cu-linked {W} chain NaCu[(HWO)(CHCOO)(OH)]·26HO (2). Electronically, the redox properties show that both compounds 1 and 2 undergo irreversible reductions resulting in the demetalation of the compounds, whilst the magnetic behavior of 1 and 2 shows a weak antiferromagnetic and a stronger ferromagnetic coupling, respectively.

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.

Chemical Stabilization and Electrochemical Destabilization of the Iron Keggin Ion in Water.

The iron Keggin ion is identified as a structural building block in both magnetite and ferrihydrite, two important iron oxide phases in nature and in technology. Discrete molecular forms of the iron Keggin ion that can be both manipulated in water and chemically converted to the related metal oxides are important for understanding growth mechanisms, in particular, nonclassical nucleation in which cluster building units are preserved in the aggregation and condensation processes. Here we describe two iron Keggin ion structures, formulated as [BiFeOFeO(OH)(CFCOO)(HO)] (Kegg-1) and [BiFeOFeO(OH)(CFCOO)] (Kegg-2).

Contrasting ion-association behaviour of Ta and Nb polyoxometalates.

Small-angle X-ray scattering (SAXS) studies of aqueous [Ta6O19](8-) compared to prior studies of aqueous [Nb6O19](8-) reveals key differences in behaviour, which is likely at the root of the difficultly in developing polyoxotantalate chemistry. Specifically, where contact ion-pairing dominates between [Nb6O19](8-) and its counterions, solvent-separated ion-pairing between [Ta6O19](8-) and its counterions has been unveiled in the current study.

Assembly and core transformation properties of two tetrahedral clusters: [Fe(III)13P8W60O227(OH)15(H2O)2]30- and [Fe(III)13P8W60O224(OH)12(PO4)4]33-.

Two nanosized 2.6 nm Fe(III) substituted polyoxotungstates [Fe(III)13P8W60O227(OH)15(H2O)2](30-) (1) and [Fe(III)13P8W60O224(OH)12(PO4)4](33-) (2) are presented herein. Both clusters are synthesized from the reactions of trilacunary polyoxotungstate precursor [α-P2W15O56](12-) and FeCl3 under strict pH control at atmospheric pressure.

Low pH electrolytic water splitting using earth-abundant metastable catalysts that self-assemble in situ.

Typical catalysts for the electrolysis of water at low pH are based on precious metals (Pt for the cathode and IrO2 or RuO2 for the anode). However, these metals are rare and expensive, and hence lower cost and more abundant catalysts are needed if electrolytically produced hydrogen is to become more widely available. Herein, we show that electrode-film formation from aqueous solutions of first row transition metal ions at pH 1.

Exploring the assembly of supramolecular polyoxometalate triangular morphologies with Johnson solid cores: [(Mn(II)(H2O)3)2(K⊂{α-GeW10Mn(II)2O38}3)]19-.

A new polyoxometalate (POM) cluster compound is presented which incorporates a trimeric assembly of Keggin-type germanotungstate fragments trapping a Johnson-type solid {Mn8} core. The mixed K-Li salt of the polyanion [(Mn(II)(H2O)3)2(K⊂{α-GeW10Mn(II)2O38}3)](19-) was characterized in the solid state and solution. The correlation of the assembly processes and the observed architecture of the "trinity" family of POMs is discussed.

The use and misuse of photosynthesis in the quest for novel methods to harness solar energy to make fuel.

This short review will illustrate that photosynthesis can provide a real contribution towards our sustain- able, green fuel requirements in the future. However, it is argued that the focus on biofuels is misplaced and that, in the longer term, investment in artificial photosynthesis will prove much more beneficial.