Exploring the Water Oxidation Catalytic Activity of a Mn-Based Magnetic Metal-Organic Framework: The Role of Proton Conductivity and Oxygen Evolution Reaction Overpotential.

The present work evaluates the water oxidation catalytic activity of a Mn-based metal-organic framework (MOF), which we envisioned to reduce the oxygen evolution reaction (OER) overpotential because of its high electrical conductivity, facilitated by solvent-encapsulated structural features. The presence of Mn centers induces interesting magnetic features in the MOF, which exhibits impressive cryogenic magnetic refrigeration with a Δ value of 29.94 J kg K for a field change of Δ = 5T at 2.

Molecular Parameters Promoting High Relaxivity in Cluster-Nanocarrier Magnetic Resonance Imaging Contrast Agents.

We have investigated the mechanism of relaxivity for two magnetic resonance imaging contrast agents that both employ a cluster-nanocarrier design. The first system termed MnFe-coPS comprises the cluster MnFeO(L)(HO) or MnFe () (L = carboxylate) co-polymerized with polystyrene to form ∼75 nm nanobeads. The second system termed MnBpy-PAm used the cluster Mn(OCCH)(Bpy) or MnBpy () where Bpy = 2,2'-bipyridine, entrapped in ∼180 nm polyacrylamide nanobeads.

Predicting the Solubility of Inorganic Ion Pairs in Water.

Polyoxometalates (POMs), ranging in size from 1 to 10's of nanometers, resemble building blocks of inorganic materials. Elucidating their complex solubility behavior with alkali-counterions can inform natural and synthetic aqueous processes. In the study of POMs ([Nb O H ] , Nb ) we discovered an unusual solubility trend (termed anomalous solubility) of alkali-POMs, in which Nb is most soluble with the smallest (Li ) and largest (Rb/Cs ) alkalis, and least soluble with Na/K .

Polyoxoniobates as molecular building blocks in thin films.

Niobium oxide thin films have been prepared by spin-coating aqueous solutions of tetramethylammonium salts of the isostructural polyoxometalate clusters [NbO], [TiNbO] and [TiNbO] onto silicon wafers, and annealing them. The [NbO] cluster yields films of NbO in the orthorhombic and monoclinic crystal phases when annealed at 800 °C and 1000 °C, respectively, whereas the [TiNbO] and [TiNbO] clusters yield the monoclinic crystal phases of TiNbO and TiNbO (titanium-niobium oxides) in different ratios. We also demonstrate a protocol for depositing successive layers of metal oxide films.

The Smallest Polyoxotungstate Retained by TRIS-Stabilization.

A polycondensation reaction of the orthotungstate anion WO, buffered at pH 7.5 in a TRIS-HCl (0.15 M) solution, results in the first example of a discrete polyoxotungstate anion, with just two W ions stabilized with TRIS ligands.