Synthesis and characterization of a new transition-metal complex of the Lindqvist polyanion Na[Cu(1, 3-pda)2]3[HNb6O19] · 3H2O

A new transition-metal (TM) complex of the Lindqvist polyanion Na[Cu(1, 3-pda)₂]₃[HNb₆O₁₉] · 3H₂O (1, 3-pda = 1, 3-diaminopropane) has been prepared using pre-prepared TBA₄[H₄Nb₆O₁₉] · 7H₂O as a precursor and characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, and thermogravimetric analysis. Crystal data for the compound: rhombohedral, space group R-3c, a = 14.927(4) Å, b = 14.927(4) Å, c = 36.940(18) Å, γ = 120°, V = 7128(4) ų, Z = 6. The structural unit of the title compound consists of a polyanion [HNb₆O₁₉]^7?, a Na⁺, three [Cu(1, 3-pda)₂]²⁺, and three crystal water molecules. The occupancy of all Cu atoms and water molecules is 0.5. X-ray diffraction indicated that the cations and the polyanion were linked through electrostatic interactions and intermolecular forces.     

铌多酸三维框架材料的研究进展

铌多酸三维框架材料是近年来无机合成化学与材料化学领域的研究热点. 该类材料不但可以将铌多酸的优异特性与框架结构的优点复合起来, 而且在光催化、 主客体化学、 能源转化等领域具有重要的应用前景. 本文总结了近10年来铌多酸三维框架材料的研究进展, 包括了该类材料的合成策略、 结构调控、 性质及应用探索. 此外, 还对当前该类材料的发展所面临的挑战进行了总结, 并对其发展前景进行了展望.     

A polyoxoniobate based on dimeric hexanionbate: [Cu(en)2]4{[Nb6O19H2]K(H2O)5}2 · (H2en) · 17H2O

A polyoxoniobate, [Cu(en)₂]₄{[Nb₆O₁₉H₂]K(H₂O)₅}₂ ? (H₂en) ? 17H₂O (en = ethylenediamine) (1), has been synthesized and characterized by elemental analysis, IR, XPS, TGA, and single-crystal X-ray diffraction. Compound 1 crystallizes in the triclinic system, space group P 1, with a = 12.3533(16) Å, b = 12.7188(16) Å, c = 29.626(4) Å, α = 93.235(2)°, β = 96.094(1)°, γ = 106.098(2)°, V = 4429.0(10) ų, Z = 2. The polyoxoanion is composed of a Lindqvist-type [Nb₆O₁₉H₂]^6? dimer bi-bridged via two K⁺. K⁺ is 10-coordinate with 10 oxygens, three from one [Nb₆O₁₉H₂]^6?, one from a terminal oxygen of another [Nb₆O₁₉H₂]^6? moiety, and the other six from water molecule. Adjacent dimeric polyoxoanions are linked to form an infinite 1-D chain via O–H ··· O hydrogen-bonding interactions which exist between the two water trimers and the dimeric polyoxoanions.     

Inorganic–Organic Hybrid Polyoxoniobates: Polyoxoniobate Metal Complex Cage and Cage Framework

The combination of polyoxoniobates (PONbs) with 3d metal ions, azoles, and organoamines is a general synthetic procedure for making unprecedented PONb metal complex cage materials, including discrete molecular cages and extended cage frameworks. By this method, the first two PONb metal complex cages K₄@{[Cu₂₉(OH)₇(H₂O)₂(en)₈(trz)₂₁][Nb₂₄O₆₇(OH)₂(H₂O)₃]₄} and [Cu(en)₂]@{[Cu₂(en)₂(trz)₂]₆(Nb₆₈O₁₈₈)} have been made. The former exhibits a huge tetrahedral cage with more than 120 metal centers, which is the largest inorganic–organic hybrid PONb known to date. The later shows a large cubic cage, which can act as building blocks for cage‐based extended assembly to form a 3D cage framework {[Cu(en)₂]@{[Cu₂(trz)₂(en)₂]₆[H₁₀Nb₆₈O₁₈₈]}}. These materials exhibit visible‐light‐driven photocatalytic H₂ evolution activity and high vapor adsorption capacity. The results hold promise for developing both novel cage materials and largely unexplored inorganic–organic hybrid PONb chemistry.     

High‐dimensional Polyoxoniobates Constructed from Lanthanide‐incorporated High‐nuclear {[Ln(H2O)4]3[Nb24O69(H2O)3]2} Secondary Building Units

In this work, two rare high‐dimensional polyoxoniobates with formulas of H₉[Cu(en)(H₂O)₂][Cu(en)₂]₈[Dy(H₂O)₄]₃[Nb₂₄‐O₆₉(H₂O)₃]₂ ? 36H₂O ( 1 ) and H₉K[Cu(en)₂(H₂O)]₅[Cu(en)₂]₄‐[Eu(H₂O)₄]₃[Nb₂₄O₆₉(H₂O)₃]₂ ? 2en ? 45H₂O ( 2 ) have been obtained under hydrothermal conditions. These extended materials are constructed from lanthanide‐incorporated triangular‐prism‐like polyoxoniobate secondary building units (SBUs) {[Ln(H₂O)₄]₃[Nb₂₄O₆₉(H₂O)₃]₂} (Ln=Dy, Eu). 1 and 2 represent the first examples of high‐dimensional polyoxometalate materials based on such lanthanide‐incorporated triangular‐prism‐like polyoxoniobate SBUs. Furthermore, the proton conduction property and the luminescent emission of these materials were evaluated.     

A new organic–inorganic hybrid polyoxoniobate based on Lindqvist-type anion and nickel complex

A new organic–inorganic hybrid polyoxoniobate (H₂en)₂[Ni(en)₃][H₂Nb₆O₁₉] · 5.5H₂O (1) (en = ethylenediamine) has been synthesized by the diffusion method and structurally characterized by elemental analyses, infrared spectrum, ultraviolet (UV) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction, thermogravimetric (TG) analysis, and single-crystal X-ray diffraction. Crystal structure analysis reveals that 1 exhibits a 3-D supramolecular architecture constructed from Lindqvist-type [H₂Nb₆O₁₉]^6? polyoxoanions and [Ni(en)₃]²⁺ via hydrogen-bonding interactions. The XPS measurement indicates that the oxidation state of Ni is +2. TG curve of 1 exhibits two steps of weight loss. In situ UV spectra display that 1 can exist in large pH range in aqueous solution.     

A polyoxoniobate constructed from Lindqvist-type hexaniobates and copper coordinated cations

A new organic–inorganic hybrid polyoxoniobate [Cu(1,3-dap)₂(H₂O)][(H₆Nb₆O₁₉)₂Cu(1,3-dap)₂]?·?4(1,3-dap)·20H₂O (1) (1,3-dap?=?1,3-diaminopropane) has been synthesized by the diffusion method and structurally characterized by elemental analyses, infrared spectrum, ultraviolet spectroscopy, and single crystal X-ray diffraction. Crystal structure analysis reveals that 1 consists of a dimeric dumbbell anion [(H₆Nb₆O₁₉)₂Cu(1,3-dap)₂]^2?, a copper coordinated cation, four 1,3-dap ligands and 20 crystal water molecules. Neighboring units are combined via hydrogen bonds forming a 3-D supramolecular framework.     

Record High‐Nuclearity Polyoxoniobates: Discrete Nanoclusters {Nb114}, {Nb81}, and {Nb52}, and Extended Frameworks Based on {Cu3Nb78} and {Cu4Nb78}

A series containing the highest nuclearity polyoxoniobate (PONb) nanoclusters, ranging from dimers to tetramers, has been obtained. They include one 114‐nuclear {Li₈⊂Nb₁₁₄O₃₁₆}, one 81‐nuclear {Li₃K⊂Nb₈₁O₂₂₅}, and one 52‐nuclear {H₄Nb₅₂O₁₅₀}. The Nb nuclearity of these PONbs is remarkably larger than those of all known high‐nuclearity PONbs (≤32). Furthermore, the introduction of 3d Cu²⁺ ions can lead to the generation of extended inorganic–organic hybrid frameworks built from novel, high‐nuclearity, nanoscale heterometallic PONb building blocks {H₃Cu₃Nb₇₈O₂₂₂} or {H₃Cu₄(en)Nb₇₈O₂₂₂}. These building blocks also contain the largest number of Nb centers of any heterometallic PONbs reported to date. The synthesis of new‐type PONbs has long been a challenging subject in PONb chemistry.     

Photochromic Polyoxoniobates with Photoinduced “D-f-A” Electron Transfer Mechanism

Compounds with redox activities have appealing applications in catalytic, electronic and magnetic properties, but the redox inert of polyoxoniobates (PONbs) significantly limits their applications for a long time. In this work, we are able to integrate organophosphate and lanthanide cluster into PONb to create the first family of inorganic-organic hybrid organophosphate-Ln-PONb composite clusters. These novel species not only present the first family of redox active PONbs that can be reduced to form long-lived “heteropoly blues” under ambient conditions, but also a new photochromic system. More importantly, the analyses of the electronic configurations and photochromic properties for a series of designed proof-of-concept PONbs models allow us to discover a D-f-A electron transfer mechanism, that is, photoinduced electron is transferred from a photosensitive organophosphate electron donor (D) to the Nb^V electron acceptor (A) through the unoccupied 4 f-orbitals of Ln (f). This work paves the way for developing diverse PONb-based redox materials and expanding the possibility of the applications of PONbs in the redox chemistry.