Designed Syntheses of Three {Ni6PW9}-Based Polyoxometalates, from Isolated Cluster to Cluster-Organic Helical Chain

Three new hexa-Ni-substituted Keggin-type polyoxometalates (POMs), [Ni6(OH)3- (DACH)3(H2O)6(PW9O34)]·31H2O (1), [Ni(DACH)2][Ni6(OH)3(DACH)3(HMIP)2(H2O)2(PW9O34)]·56 H2O (2), and [Ni(DACH)2][Ni6(OH)3(DACH)2(AP)(H2O)5(PW9O34)]·2H2O (3) (DACH = 1,2-Diami- nocyclohexane, MIP = 5-Methylisophthalate, AP = Adipate) were successfully made in the presence of DACH under hydrothermal conditions. 1 is an isolated hexa-Ni-substituted Keggin unit decorated by DACH. In order to further construct POM cluster-organic frameworks (POMCOFs) on the basis of 1, by analyzing the steric hindrances and orientations of the POM units, the rigid HMIP and flexible AP ligands were successively incorporated, and another anionic monomeric POM 2 and the new 1D POM cluster organic chain (POMCOC) 3 were obtained. HMIP ligand still acts as a decorating group on the Ni6 core of 2 but results in the different spatial arrangement of the {Ni6PW9} units. AP ligands in 3 successfully bridge adjacent isolated POM cluster units to 1D POMCOC with left-hand helices. The AP in 3 is the longest aliphatic carboxylic acid ligand in POMs, and the 1D POM cluster-AP helical chain represents the first 1D POMCOC with a helical feature.

A Keggin-type polyoxomolybdate-based crystalline material formed by hydrothermal transformation: photo/electro-catalytic properties and mechanism study

This study constructs a POM-based crystalline material of [(SiMo12O40)Cu6(2,2′-bipy)6(Mo6O22)] (1). The photocatalytic MB degradation and electrocatalytic nitrite reduction properties of complex 1 are systematically studied for the first time.

Surfactant-assisted fabrication and supercapacitor performances of a 12-phosphomolybdate-pillared metal–organic framework containing a helix and its SWNT nanocomposites

By employing a surfactant-assisted hydrothermal method, a new POMOF with a multi-fold helix was obtained, and NiPMo12/SWNTs exhibits excellent electrochemical performance and good stability as an electrode material for supercapacitors.

Two Ni-Substituted Trilacunary Keggin-Type Polyoxometalates: Syntheses, Crystal Structures, NLO Studies, and Magnetic Properties

Two Ni-substituted polyoxometalates (NiSPs), [Ni₆(Py)₆(H₂O)₅(μ₃-OH)₃(PW₉O₃₄)]₂·10H₂O (1), [Ni₇(Py)₆(Im)(H₂O)₅O(WO₄)(μ₃-OH)₃(H₂PW₉O₃₄)]·3H₂O (2) (Py = pyridine, Im = imidazole), were successfully hydrothermally synthesized. Compounds 1 and 2 have significantly different configurations by introducing different amounts of imidazole ligands. For compound 1, two malposed {Ni₆(Py)₆PW₉} units that are face to face are bridged by two Ni-O-W bonds to constitute an isolated dimeric structure. Differently, the {Ni₇(Py)₆(Im)PW₉}₂ dimer in compound 2 connects with four adjacent dimers by four {WO₄} groups in an interesting two-dimensional (2-D) arrangement. The magnetism of compounds 1 and 2 was studied, and magnetic test results demonstrated that both compounds have ferromagnetic interactions between the nickel centers. Meanwhile, the third-order nonlinear optical (NLO) measurements indicated that compound 1 can serve as potential nonlinear optical materials.

{Cu8} Cluster-Sandwiched Polyoxotungstates and Their Polymers: Syntheses, Structures, and Properties

Four inorganic-organic hybrid octa-Cu cluster sandwiched polyoxotungstates (POTs), [Cu₈(H₂O)₂(en)₄(B-α-H₂SiW₉O₃₄)₂] (1), [Cu₈(H₂O)₂(en)₄(B-α-H₂GeW₉O₃₄)₂] (2), K₂[Cu₈(en)₄(B-α-HSiW₉O₃₄)₂]·6H₂O (3), and K₂[Cu₈(en)₄(B-α-HGeW₉O₃₄)₂]·2H₂O (4) (en = ethylenediamine), were hydrothermally made and characterized by single-crystal X-ray diffraction, infrared spectra, powder X-ray diffraction, and thermogravimetric analysis, respectively. Structure analysis reveals that the polyoxoanion of 1/2 is a discrete dimer built by two trivalent Keggin [B-α-XW₉O₃₄]^10- (X = Si/Ge) fragments and one octa-Cu cluster, whereas 3 and 4 display a two-dimensional network built by octa-Cu-sandwiched POT units via substitution of coordinated water on polyanions of 1 and 2 and further expand into a three-dimensional framework via K cation bridges. Ultraviolet-visible diffuse reflectance spectra reveal that 1-4 are potential semiconductor materials. Moreover, its visible light-driven catalytic H₂ evolution activity, electrochemical properties, catalysis for oxygenation reactions of thioethers, and magnetic behaviors have been investigated in detail.

Assembly, structures and properties of polyoxometalate-based supramolecular complexes involving in situ transformation of single-branch N-donor cyano ligands

A series of polyoxometalate-based supramolecular complexes were prepared with in situ transformation of single-branch N-donor cyano ligands, exhibiting diverse structures and good electrocatalytic and photocatalytic properties.