170 research outputs found
A Lewis acid catalytic core sandwiched by inorganic polyoxoanion caps: selective H2O2-based oxidations with [AlIII4(H2O)10(β-XW9O33H)2]6− (X = AsIII, SbIII)
No full textThe Al-III-containing polyanions [Al-4(III)(H2O)(10)(beta-XW9O33H)(2)](4-) with X=As-III (1) and Sb-III (2) feature four aluminum(III) centers sandwiched by two trivacant (beta-XW9O33) Keggin units, and trigger peroxide catalysis as well as substrate coordination via multiple Lewis acid site interactions
Photocatalytic Water Oxidation by a Mixed-Valent (Mn3MnO3)-Mn-III-O-IV Manganese Oxo Core that Mimics the Natural Oxygen-Evolving Center
No full textThe functional core of oxygenic photosynthesis is in charge of catalytic water oxidation by a multi-redox MnIII/MnIV manifold that evolves through five electronic states (Si, where i=0-4). The synthetic model system of this catalytic cycle and of its S0→S4 intermediates is the expected turning point for artificial photosynthesis. The tetramanganese-substituted tungstosilicate [MnIII3MnIVO3(CH3COO)3(A-α-SiW9O34)]6- (Mn4POM) offers an unprecedented mimicry of the natural system in its reduced S0 state; it features a hybrid organic-inorganic coordination sphere and is anchored on a polyoxotungstate. Evidence for its photosynthetic properties when combined with [Ru(bpy)3]2+ and S2O82- is obtained by nanosecond laser flash photolysis; its S0→S1 transition within milliseconds and multiple-hole-accumulating properties were studied. Photocatalytic oxygen evolution is achieved in a buffered medium (pH 5) with a quantum efficiency of 1.7 %
Transition metal containing silico- and germanotungstates
No full textThis work focuses on the interaction of the versatile dilacunary silicotungstate unit with different metal cations leading to novel compounds interesting for magnetic and catalytic applications. Also this work reports two new lanthanide containing polytungstates, a sandwich type silicotungstate and a dimeric-pentameric germanotungstate. The 15-cobalt-substituted polyoxotungstate (1) has a core of nine CoII ions encapsulated by three unprecedented fragments and two Chloro ligands. The 6-cobalt-substituted silicotungstate (2) contains three cobalt ions which are encapsulated between an unprecedented fragment and a lacunary unit. The new, monometal substituted silicotungstates (3-5) are composed of two units fused on one side via two W-O-W' bridges and on the other side by an octahedrally coordinated transition metal fragment. The trimeric species (6) consists of three units linked by an unprecedented Zr6 cluster with C1 point group symmetry. The dimeric species (7) consists of two units sandwiching a Zr4 cluster and has also C1 symmetry. The unprecedented peroxo-zirconium(IV) containing silicotungstate (8) comprises a cyclic 6-peroxo-6-zirconium core stabilized by three decatungstosilicate units and represents the first structurally characterized Zr-peroxo POM with side-on, bridging peroxo units. The mono-lanthanide containing polyanions (9-16) have also been syntesized. Larger Ln3+ ions appear to favor an R,R (or S,S) configuration (point group C2) of the Keggin units, with an increasing amount of R,S (or S,R) configuration (point group C1) found in the solid state as the Ln3+ ion decreases in size. Finally, The gigantic 20-cerium(III) containing 100-tungstogermanate (17) represents the first lanthanide substituted tungstogermanate and it is one of the largest polytungstates reported to date
Synthesis and Characterization of 8-Yttrium(III)-Containing 81-Tungsto-8-Arsenate(III), [Y8(CH3COO)(H2O)18(As2W19O68)4(W2O6)2(WO4)]43−
No full textThe 8-yttrium(III)-containing 81-tungsto-8-arsenate(III) [Y8(CH3COO)(H2O)18(As2W19O68)4(W2O6)2(WO4)]43− (1) has been synthesized in a one-pot reaction of yttrium(III) ions with [B-α-AsW9O33]9− in 1 M NaOAc/HOAc buffer at pH 4.8. Polyanion 1 is composed of four {As2W19O68} units, two {W2O10} fragments, one {WO6} group, and eight YIII ions. The hydrated cesium-sodium salt of 1 (CsNa-1) was characterized in the solid-state by single-crystal XRD, FT-IR spectroscopy, thermogravimetric and elemental analyses
Divacant polyoxotungstates: Reactivity of the gamma-decatungstates [γ-XW10O36]8−(X = Si, Ge)
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Ti-2-Containing 18-Tungsto-2-Arsenate(III) Monolacunary Host and the Incorporation of a Phenylantimony(III) Guest
No full textThe novel Ti-2-containing, sandwich-type 18-tungsto-2-arsenate(III) [ ((TiO)-O-IV)(2) (alpha-(AsW9O33)-W-III)(2)](14-) (1) was successfully synthesized by the reaction of [TiO](2+) species with [alpha-(AsW9O33)-W-III](9-). The monolacunary polyanion 1 is solution-stable, and a further reaction with 1 equiv of phenylantimony(III) dichloride resulted in [C6H5SbIII((TiO)-O-IV)(2)(alpha-(AsW9O33)-W-III)(2)](12-) (2). Both polyanions 1 and 2 were structurally characterized in the solid state and solution. Electrochemical studies were also performed on both polyanions
ChemInform Abstract: Divacant Polyoxotungstates: Reactivity of the Gamma-Decatungstates [γ-XW10O36]8- (X: Si, Ge)
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