NiII 36 -Containing 54-Tungsto-6-Silicate: Synthesis, Structure, Magnetic and Electrochemical Studies

{SeO2(OH)} Bridging Lanthanide-Containing Antimono-Seleno-Tungstates

A series of new trigonal pyramidal {SeO2(OH)} bridging lanthanide-containing antimono-seleno-tungstates [H2N(CH3)2]8Na8Cs4H9[Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]2·32H2O [Ln = Tb (1), Dy (2), Ho (3), Er (4)] have been prepared by the synthetic strategy of simultaneously using the antimonotungstate precursor and simple material in an acidic aqueous solution and structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR spectrometry, and thermogravimetric analysis. Their molecular structures contain an unprecedented hexameric polyoxoanion [Ln2SeW4O11(OH)(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33)]229- constituted by two equivalent trimeric subunits Ln2W4O9(H2O)4(SbW9O33)(SeW9O33)(Se1/2Sb1/2W9O33) bridged via two μ2-{SeO2(OH)} linkers. Furthermore, the catalytic oxidation of various aromatic sulfides and sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES) by compound 3 as the heterogeneous catalyst has been investigated, exhibiting high conversion and selectivity as well as good stability and recyclability.

A Hexadecanuclear Cobalt-Added Tungstogermanate Containing Counter Cobalt Hydrates: Synthesis, Structure and Photocatalytic Properties

The synthesis and exploration of the properties of structurally-new polyoxometalates (POMs) has been attracting considerable research interest. In this work, a hexadecanuclear cobalt-added tungstogermanate, H₃₁(NH₄)₅Na₁₆{Co^Ⅲ(H₂O)₆}₄{[Co^Ⅱ₄(μ₃-OH)₃(PO₄)]₄(A-α-GeW₉O₃₄)₄}₂·23-H₂O (1), was synthesized under hydrothermal conditions and characterized by various techniques. Compound 1 can effectively drive the heterogeneous photocatalytic hydrogen evolution reaction in the presence of [Ir(ppy)₂(dtbbpy)][PF₆] as the photosensitizer, with triethanolamine (TEOA) and N-Hydroxy succinimide (NHS) used as the dual sacrificial reagents. Control experiments revealed the important role of NHS in enhancing the hydrogen-evolution activities. Under optimal catalytic conditions, a hydrogen yield of 54.21 μmol was achieved after 10-h photocatalysis, corresponding to a hydrogen evolution rate of 1807.07 μmol·g^-1·h^-1. Stability studies demonstrated that catalyst 1 can be isolated and reused for three successive photocatalytic cycles with negligible decline of the H₂ yield, indicating the stability and recycling robustness of catalyst 1.

Structurally-New Hexadecanuclear Ni-Containing Silicotungstate with Catalytic Hydrogen Generation Activity

A structurally-new, carbon-free hexadecanuclear Ni-containing silicotungstate, [Ni₁₆(H₂O)₁₅(OH)₉(PO₄)₄(SiW₉O₃₄)₃]^19-, has been facilely synthesized using a one-pot, solution-based synthetic method systematically characterized by single-crystal X-ray diffraction and several other techniques. The resulting complex works as a noble-metal-free catalyst for visible-light-driven catalytic generation of hydrogen, by coupling with a [Ir(coumarin)₂(dtbbpy)][PF₆] photosensitizer and a triethanolamine (TEOA) sacrificial electron donor. Under minimally optimized conditions, a turnover number (TON) of 842 was achieved for TBA-Ni₁₆P₄(SiW₉)₃-catalyzed hydrogen evolution system. The structural stability of TBA-Ni₁₆P₄(SiW₉)₃ catalyst under photocatalytic conditions was evaluated by the mercury-poisoning test, FT-IR, and DLS measurements. The photocatalytic mechanism was elucidated by both time-solved luminescence decay and static emission quenching measurements.

High-Nuclear Ni-Substituted Poly(polyoxometalate) Containing an Anderson-like {Cs7} Cluster

A novel high-nuclear Ni-substituted poly(polyoxometalate) [poly(POM)], [H₂N(CH₃)₂]₂Na₁₈Cs₂H₁₃[(Cs₇(H₂O)₆)@{(PO₄)-@(Ni₄(OH)₃(WO₄))₃@(B-α-PW₉O₃₄)₃}₂]·30H₂O (1), has been successfully developed and structurally characterized. The polyoxoanion of 1 can be viewed as a unique huge sandwich structure made of an unprecedented Cs₇(H₂O)₆ ({Cs₇}) cluster core encapsulated by two trimeric [(PO₄)@(Ni₄(OH)₃(WO₄))₃@(B-α-PW₉O₃₄)₃]^21- subunits, in which the {Cs₇} cluster presents an interesting Anderson-like arrangement and is the first example of a classical POM configuration based on the alkali metal cluster in the POM chemistry. The polyoxoanion can also be described as an unusual [(Cs₇(H₂O)₆)@{(PO₄)@(Ni₄(OH)₃(WO₄))₃}₂]¹⁹⁺ cluster packaged by six {PW₉} fragments. Furthermore, investigations on the Knoevenagel condensation reaction reveal that 1 has good catalytic activity for the condensation of various aldehydes and malononitrile into corresponding products with excellent yields.

Synergic coordination of multicomponents for the formation of a {Ni30} cluster substituted polyoxometalate and its in situ assembly

The synergic coordination of trz, en, and PW9 resulted in a {Ni30} cluster substituted POM, [Ni(trz)3]2@[Ni30(H2O)16]POM, that was discovered as the SBU of four frameworks which served as heterogeneous catalysts for HERs.