Polyoxometalate-mediated syntheses of three structurally new silver clusters.

Three structurally new polyoxometalate-templated silver clusters, homometallic [(SiW9O34)@Ag24(iPrS)11(DPPP)6Cl]2(SiW12O40) (Ag24), heterometallic [(SiW9O34)@Ag22Cu(iPrS)11(DPPP)6Cl](SbF6)2 (Ag22Cu) and {Ag16(iPrS)6(DPPP)8(CH3COO)4[Co4(OH)3(H2O)SiW9O33]2}·(CH3CN)4 (Ag16Co8) (iPrS- = isopropanethiolate, DPPP = 1,3-bis(diphenylphosphino)propane, SbF6- = hexafluoroantimonate) have been successfully synthesized using a facile solvothermal approach. The introduction of copper and cobalt ions can induce obvious changes in the molecular configuration of the obtained clusters, leading to distinct temperature-dependent photoluminescence and photothermal conversion properties.

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.

All-Inorganic Bis-Sb3O3-Functionalized A-Type Anderson-Evans Polyoxometalate for Visible-Light-Driven Hydrogen Production.

An all-inorganic, novel bis-Sb3O3-functionalized A-type Anderson-Evans polyoxometalate, [Ni(H2O)6]KH[NiMo6O24(Sb3O3)2]·5H2O (1), has been synthesized under hydrothermal conditions. The chemical composition, molecular structure, and elemental oxidation states of the resulting compound have been systematically characterized by various techniques, including single-crystal X-ray diffraction, thermogravimetric analysis, Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy. The title complex 1 has been investigated for the first time as a catalyst for visible-light-driven hydrogen production by coupling with a [Ir(coumarin)2(dtbbpy)][PF6] photosensitizer and a triethanolamine (TEOA) sacrificial electron donor. Under minimally optimized conditions, a H2 generation rate of as high as 10 358 µmol g-1 h-1 is achieved during a 6 h photocatalysis. Additional control experiments and spectroscopic analyses have demonstrated that complex 1 will undergo the in situ photoreduction during photocatalysis and its specific geometric structure is essential to efficient photocatalysis for H2 production.

One-Step versus Two-Step Valence Tautomeric Transitions in Tetraoxolene-Bridged Dinuclear Cobalt Compounds.

The syntheses of valence tautomeric compounds with multistep transitions using new redox-active ligands are the long-term goal of the field of bistable materials. The redox-active tetraoxolene ligand, 2,7-di-tert-butylpyrene-4,5,9,10-tetraone (pyreneQ-Q), is now developed to synthesize a pair of dinuclear compounds {[CoL2]2(pyreneSq-Sq)}[Co(CO)4]2·xCH2Cl2·2C6H5CH3 (1, x = 2, L = 1,10-phenanthroline, phen; 2, x = 1.5, L = 2,2'-bipyridine, bpy). Variable-temperature magnetic susceptibilities and single-crystal X-ray diffraction measurements indicate a partial one-step valence tautomeric transition for 1 and a rare two-step valence tautomeric transition for 2, respectively. DFT calculation results are consistent with the experimental data, revealing the correlation between thermodynamic parameters and the one-step/two-step valence tautomeric behaviors.