Crystal structure and electrochemistry properties of one two-dimensional heteropolyoxoniobate based on four- and five-vanadium-capped Keggin anions

One two-dimensional heteropolyoxoniobate compound [Cu(H4dap)2(H2O)]8{K[Cu(H3dap)2]4}2[VNb12O40(VO)4]3[VNb12O40(VO)4(VO)](OH)939H2O (1) (H4dap = 1,2-diaminopropane) was obtained by hydrothermal method. In this mixed 2D layer, the ratio of four- and five-vanadium-capped Keggin heteropolyoxoniobates is 3:1. Compound...

Synthesis, cytotoxicity, apoptosis and cell cycle arrest of a ruthenium multi-substituted Keggin-type polyoxotungstate

The ruthenium multi-substituted polyoxotungstate with chemical formulae of K7[SiW9O37Ru4(H2O)3Cl3]·15H2O (S1) was synthesized by a conventional aqueous solution containing the trilacunary Keggin-anions β-Na9HSiW9O34·12H2O(S2) and RuCl3·nH2O(S3). Compound S1 was characterized by elemental analyses, EDS, TG analyses, IR, UV/Vis and XPS. The cytotoxic potential of compound S1 was tested on C33A, DLD-1, HepG-2 cancer cells and human normal embryonic lung fibroblasts cell MRC-5. The viability of the treated cells was evaluated by MTT assay. The mode of cell death was assessed by morphological study of DNA damage and apoptosis assays. Compound S1 induced cell death in a dose-dependent manner, and the mode of cell death was essentially apoptosis though necrosis was also noticed. Cell cycle analysis by flow cytometry indicated that compound S1 caused cell cycle arrest and accumulated cells in S phase.

Coordination capacity of Keggin anions as polytopic ligands: case study of [VNb12O40]15–

Reaction of Na9H4[VNb12O40{NbO(CO3)}2] with [(C6H6)RuCl2]2 (molar ratio {VNb12}:{(C6H6)Ru} = 1:4) in aqueous solution gives a mixture of [α-{(C6H6)Ru}4VNb12O40]7– and [α-{(C6H6)Ru}3VNb12O40]9–. Direct acetone diffusion into mother liquor leads to crystallization of...

Oxygen Adsorption and Activation on Cobalt Center in Modified Keggin Anion-DFT Calculations

The influence of the cobalt cation geometric environment on catalytic activity, namely, oxygen adsorption and its activation, was investigated by exploring two groups of systems. The first group was formed by cobalt cation complexes, in which the Co2+ was surrounded by water-H2O or acetonitrile-CH3CN solvent molecules. This represents heteropolyacids salts (ConH3-nPW(Mo)12O40), where the Co2+ acts as a cation that compensates for the negative charge of the Keggin anion and is typically surrounded by solvent molecules in that system. The second group consisted of tungsten or molybdenum Keggin anions (H5PW11CoO39 and H5PMo11CoO39), having the Co2+ cation incorporated into the anion framework, in the position of one addenda atom. Detailed NOCV (Natural Orbitals for Chemical Valence) analysis showed that, for all studied systems, the σ-donation and σ-backdonation active channels of the electron transfer were responsible for the creation of a single Co-OO bond. Depending on the chemical/geometrical environment of the Co2+ cation, the different quantities of electrons were flown from the Co2+ 3d orbital to the π* antibonding molecular orbitals of the oxygen ligand, as well as in the opposite direction. In molybdenum and tungsten heteropolyacids, modified by Co2+ in the position of the addenda atom, activation of O2 was supported by a π-polarization process. Calculated data show that the oxygen molecule activation changed in the following order: H5PMo11CoO39 = H5PW11CoO39 > Co(CH3CN)52+ > Co(H2O)52+.

Four Keggin-based compounds constructed by a series of pyridine derivatives: synthesis, and electrochemical, photocatalytic and fluorescence sensing properties

Four compounds based on Keggin anions and AgI ions were obtained, the photocatalytic and electrochemical properties were studied. Compound 4 can act as a Hg2+ fluorescence sensor.

A Charge-Transfer Salt Based on Ferrocene/Ferrocenium Pairs and Keggin-Type Polyoxometalates

A new hybrid inorganic-organometallic salt has been obtained from the reaction of the Keggin-type silicotungstate anion with ferrocene in a water/methanol mixture as a result of the partial oxidation of ferrocene molecules to ferrocenium cations. Single-crystal X-ray diffraction analysis reveals the presence of four ferrocenium (FeIII) cations and one ferrocene (FeII) molecule per plenary Keggin anion in the crystal structure of [FeIII (Cp)2]4[SiW12O40]·[FeII(Cp)2]·2CH3OH (1). Compound 1 thus constitutes the first example in the literature in which ferrocenium and ferrocene species coexist in the structure of a polyoxometalate-based salt. The two crystallographically independent ferrocenium species in the asymmetric unit of 1 exhibit different configurations: One displays an eclipsed conformation with ideal D5h symmetry, whereas the conformation in the other one is staggered D5d. The crystal packing of 1 can be best described as an organometallic sub-lattice of ferrocenium and ferrocene species linked by a network of π-π interactions that generates rectangular cavities of about 14 × 10 Å in which strings of Keggin anions and methanol molecules are hosted, further connected to each other via weak OPOM···CMeOH-OMeOH···OPOM type hydrogen bonds. The charge-transfer nature of the salt has been studied by solid-state diffuse reflectance UV-Vis spectroscopy and the presence of magnetically isolated FeIII/FeII centres has been confirmed by Mössbauer spectroscopy. A topological study carried out on all of the pristine ferrocenyl species deposited in the Cambridge Structural Database (CSD) has allowed two main conclusions to be drawn: (1) these species tend to adopt extreme conformations (either eclipsed or staggered) with less than a 15% of examples showing intermediate states and (2) the oxidation state of the iron centres can be unequivocally assigned on the basis of a close inspection of the Fe···Cp distances, which allows ferrocene neutral molecules and ferrocenium cations to be easily distinguished.

Amperometric sensing and photocatalytic properties under sunlight irradiation of a series of Keggin–AgI compounds through tuning single and mixed ligands

In this work, we synthesized eight compounds based on Keggin anions and AgI ions by introducing La and Lb.