Covalent organic-inorganic polyoxometalate hybrids in catalysis.

Polyoxometalates (POMs) are a class of compounds known for the vast range of tunable structures and properties available, leading to applications in areas such as catalysis, energy, and advanced medicine. The ability to covalently functionalize POMs with organic components has been investigated extensively to tune the physical and chemical properties of the resulting hybrid materials. These hybrids, where the organic entity is covalently attached to the POM-core ( hybrid POMs) result in a vast library of promising customizable catalytic systems, displaying tunable properties with a high level of synergy between the polyanion and the organic component.

Trigonal Prismatic Coordination of Discrete Rare Earth Ions, Enforced by the Polyoxotungstate [P W O (H O)].

A family of solution-stable polyanions [Na⊂{Ln (H O)}{W O(H O)}P W O ] (Ln=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) represent the first examples of polyoxometalates comprising a single lanthanide(III) or yttrium(III) ion in a rare trigonal prismatic O environment. Their synthesis exploits the reactivity of the organophosphonate-functionalized precursor [P W O (C H P O) ] with heterometal ions and yields hydrated potassium or mixed lithium/potassium salts of composition K Ln H [Na⊂{Ln(H O)}{WO(H O)}P W O ]⋅nH O⋅mLiCl (x=8.5-11; y=0-2; n=24-34; m=0-1.

Polyoxotungstate Archetype {P W } and its 3d Derivatives.

The propensity of the new, phenylphosphonate-stabilized polyoxotungstate [(C H P O) P W O ] to act as a precursor for new 3d metal-functionalized polyanions has been investigated. Reactions with Mn and Cu induce the formation of the previously unknown polyoxotungstate archetype {P W }, isolated as salts of the polyanions [Na⊂{Mn (H O)}{WO(H O)}P W O ] (1) and [K⊂{Cu (H O)}{W(OH)(H O)}P W O ] (2), which were characterized in the solid state (single-crystal X-ray diffraction, elemental and TG analyses, IR spectroscopy, SQUID magnetometry) and in aqueous solution (UV/Vis spectroscopy, cyclic voltammetry).

Sequential Isomerization of a Macrocyclic Polyoxometalate Archetype.

Controlled isomerization of individual {α-PWO} polyoxotungstate building blocks under the constricted conditions of the macrocyclic [PWO] archetype ({PW}) is linked to site-specific Cu coordination. The derivatives [-PWO{Cu(HO)}] (), [-PWO{Cu(HO)}] (), and [-PWO{Cu(HO)}] () feature the {αγαγ-PW} and the hitherto unknown {-PW} and {-PW} isomers based on {α-PW} and/or Cu-stabilized {γ-PW} units and form from the reactions of the classical {PW} (={-PW}) and CuCl in sodium acetate medium (pH 5.2).