Studies on fibrillar form of trimolybdate Rb2O · 3MoO3 · H2O

The fibrillar rubidium trimolybdate was investigated. Its structure has been discussed on the basis of X-ray, thermogravimetric, IR and NMR measurements.     

Highly sensitive electrochemiluminescence “turn-on” aptamer sensor for lead(II) ion based on the formation of a G-quadruplex on a graphene and gold nanoparticles modified electrode

We have developed a “turn on” model of an electrochemiluminescence (ECL) based assay for lead ions. It is based on the formation of a G-quadruplex from an aptamer labeled with quantum dots (QDs) and placed on an electrode modified with of graphene and gold nanoparticles (AuNPs). A hairpin capture probe was labeled with a thiol group at the 5′-end and with an amino group at the 3′-end. It was then self-assembled on the electrode modified with graphene and AuNPs. In the absence of Pb(II), the amino tag on one end of the hairpin probe is close to the surface of the electrode and therefore unable to interact with the QDs because of steric hindrance. The ECL signal is quite weak in this case. If, however, Pb(II) is added, the stem-loop of the aptamer unfolds to form a G-quadruplex. The amino group at the 3′-end will become exposed and can covalently link to a carboxy group on the surface of the CdTe QDs. This leads to strong ECL. Its intensity increases (“turns on”) with the concentration of Pb(II). Such a “turn-on” method does not suffer from the drawbacks of “turn-off” methods. ECL intensity is linearly related to the concentration of Pb(II) in the 10 p mol·L^?1 to 1 n mol·L^?1 range, with a 3.8 p mol·L^?1 detection limit. The sensor exhibits very low detection limits, good selectivity, satisfying stability, and good repeatability.

An organic-inorganic hybrid polyoxometalate based on the dodecatungstate building block: [Ni(phen)(H2O)3]2[Ni(H2O)5][H2W12O40] · 6H2O

An organic-inorganic hybrid polyoxometalate [Ni(phen)(H₂O)₃]₂[Ni(H₂O)₅][H₂W₁₂O₄₀]?·?6H₂O (phen?=?1,10-phenanthroline) has been isolated and characterized by IR, UV, electrochemistry and single-crystal X-ray diffraction. X-ray crystallographic study indicates that the title compound is monoclinic, space group C2/c, with lattice constants a?=?21.7672(17), b?=?16.1189(12), c?=?20.7949(16)?Å, β?=?107.8440(10)°, V?=?6945.2(9)?ų, D _c?=?3.528?Mg?m^?3, F(000)?=?6600, Z?=?4, R ₁?=?0.0372, wR ₂?=?0.0845. The molecular fragment of the title compound consists of two supporting [Ni(phen)(H₂O)₃]²⁺ coordination cations, one supporting [Ni(H₂O)₅]²⁺ unit, one metatungstate polyoxoanion [H₂W₁₂O₄₀]^6? and six H₂O molecules of crystallization.     

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.     

Surface organometallic chemistry: Reductive carbonylation of OsCl3·3H2O supported on silica

The reductive carbonylation of silica-supported OsCl₃·3H₂O was investigated under atmospheric pressure of CO or of a mixture of CO and H₂O at relatively mild temperatures. Starting from OsCl₃·3H₂O a mixture of physisorbed α-[Os(CO)₃Cl₂]₂, cis-[Os(CO)₄Cl₂] and a species bound to the surface silanol groups, [Os(CO)₃Cl₂(HOSi)], is formed working at 100°C under CO. At higher temperatures [Os(CO)₃Cl₂(HOSi)] is the major surface species. Attempts to reduce further on the surface these Os^II chlorocarbonyl species failed due to their easy sublimation and to the difficult removal of the chloro ligands. However, when the silica is treated with a weak base such as NaHCO₃, α- or β-[Os(CO)₃Cl₂]₂ supported on silica may be reduced with CO to [Os₃(CO)₁₂], with CO and H₂O to a mixture of [OS₃(CO)₁₂] and [H₄Os₄(CO)₁₂], and finally with H₂ to [H₄Os₄(CO)₁₂]. These reduction processes occur via the anchored [Os(CO)₃(OSi)₂]_n species, as intermediate surface species.     

Highly sensitive electrochemical sensor based on β-cyclodextrin–gold@3, 4, 9, 10-perylene tetracarboxylic acid functionalized single-walled carbon nanohorns for simultaneous determination of myricetin and rutin

The application of macrocyclic hosts for construction of different electrochemical devices and separation matrices has attracted much attentions due to their benign biocompatibility and simplicity of synthesis. Myricetin and rutin are considered two of the most bioactive flavonoids, which have been proved to exhibit various physiological functions. This work reports a simple and facile approach for the synthesis of β-cyclodextrin-gold@3, 4, 9, 10-perylene tetracarboxylic acid functionalized single-walled carbon nanohorns (β-CD–Au@PTCA–SWCNHs) nanohybrids. The simultaneous electrochemical determination of myricetin and rutin using a β-CD–Au@PTCA–SWCNHs-modified glassy carbon electrode was established. The results show that the β-CD–Au@PTCA–SWCNHs-modified electrode displayed electrochemical signal superior to those of Au@PTCA–;SWCNHs and SWCNHs towards myricetin and rutin. The proposed modified electrode has a linear response range of 0.01–10.00 μM both for myricetin and rutin with relatively low detection limits of 0.0038 μM for myricetin and 0.0044 μM (S/N = 3) for rutin, respectively. The excellent performance of the sensing platform is considered to be the synergic effects of the SWCNHs (e.g. their good electrochemical properties and large surface area) and β-CD (e.g. a hydrophilic external surface, a high supramolecular recognition, and a good enrichment capability).     

Influence of MgHPO4·3H2O and Mg3(PO4)2·8H2O on Thermal Reactions (20°-1000°C) in Solid Solutions with Al2(SO4)3·16H2O

Abstract

The following binary systems were studied: AI₂(SO₄)₃·16H₂0 - MgHPO₄·3H₂O and AI₂(SO₄)₃·16H₂O - Mg₃(P0₄)₂·8H₂0.     

Interaction of acetone, hydroxyacetone, acetaldehyde and benzaldehyde with the surface of water ice and HNO3·3H2O ice

Oxygenated volatile organic compounds (OVOCs) influence the oxidative properties of the atmosphere, and their transport from the ground may occur by scavenging by the HNO(3)-rich supercooled water droplets found in polluted convective air masses. With infrared spectroscopy, we have studied the interactions of four typical atmospheric OVOCs (acetone, hydroxyacetone, acetaldehyde and benzaldehyde) with model surfaces of water ice and of trihydrated nitric acid (NAT) ice. We show that these molecules weakly adsorb on water ice and NAT by hydrogen bonding. No chemical reaction occurs between the molecules and the NAT substrate, the OVOCs remaining intact when in contact with hydrated HNO(3) in atmospheric ice clouds.     

New multicomponent organic semiconductors based on ET with polymeric Anions: α″-(ET)2N(CN)2·2H2O and α‴-(ET)6(NO3)3·2C2H5O2N3

New multicomponent radical cation salts derived from bis(ethylenedithio)tetrathiafulvalene (ET) were prepared: bis(ethylenedithio)tetrathiafulvalene dicyanamide dihydrate α″-(ET)₂N(CN)₂·2H₂O and bis-(ethylenedithio)tetrathiafulvalene nitrate α?-(ET)₆(NO₃)₃·2C₂H₅O₂N₃ containing two biuret molecules (C₂H₅O₂N₃). The crystal structures of the compounds were determined, and their conducting properties were examined. Both salts have layered structures in which radical cation layers alternate with nonconducting anionic layers. The radical cation layers in the salts α″-(ET)₂N(CN)₂·2H₂O and α?-(ET)₆(NO₃)₃·2C₂H₅O₂N₃ are packed in the α″ and α? fashion, respectively. Anionic layers consist of polymeric chains formed by hydrogen bonding between [N(CN)₂]? anions and water molecules in α″-(ET)₂N(CN)₂·2H₂O or between NO?₃ anions and biuret molecules in α?-(ET)₆(NO₃)₃·2C₂H₅O₂N₃. Both salts show semiconductor conductivity.     

Polythermic decomposition of Co(COO)2 · 2H2O compound synthesized within pores of photonic crystals based on SiO2

Polythermic decomposition of Co(COO)₂ · 2H₂O synthesized within pores of photonic crystals based on SiO2 was studied by thermogravimetry and differential scanning calorimetry techniques in helium and air in flow and under static conditions. Efficient activation energies and dehydratation enthalpies of the photonic crystals based on SiO₂ both in the absence and in the presence of Co(COO)₂ · 2H₂O phase (23.6, 41.5 and 77.6, 49.8 kJ mol^-1, respectively) were calculated. Polythermic Co(COO)₂ · 2H2O decomposition within pores of the photonic crystallites was found to yield CoO and Co₃O₄ nanoparticles in helium and air, respectively, exhibiting higher catalytic activity in CO oxidation by molecular oxygen. A conclusion was drawn that exothermic effect in the temperature range covering dehydrated oxalate decomposition is due to heterogeneously catalytic CO oxidation on the CoO and Co₃O₄ phases.     

A three-dimensional porous metal-organic framework based on 9,9-dimethylfluorene-2,7-dicarboxylic acid (H2MFDA): {[Tb2(MFDA)3(DMF)2(H2O)3] · (H2O)3(DMF)6} n

The title metal-organic framework, [Tb₂(MFDA)₃(DMF)₂(H₂O)₃] · (H₂O)₃(DMF)₆} _n (I) (H₂MFDA = 9,9-dimethylfluorene-2,7-dicarboxylic acid, DMF = N,N-dimethylformamide), has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction (CIF file CCDC no. 995892). Complex I crystallizes in triclinic space group \(P\bar 1\) with a = 13.0022(3), b = 13.3793(3), c = 25.8929(4) Å, α = 84.060(2)°, β = 88.104(2)°, γ = 66.361(2)°, V = 4104.05(15) ų, C₇₅H₁₀₄N₈O₂₆Tb₂, M = 1851.50, ρ _c = 1.498 g/cm³, μ(MoK _α) = 1.790 mm^?1, F(000) = 1896, GOF = 1.055, Z = 2, the final R ₁ = 0.0522 and wR ₂ = 0.1380 for I > 2σ(I). In MOF I, the Tb₂ dinuclear units double-bridged by two carboxylate groups are connected together by MFDA ligands to give rise to a 3D architecture that consists in two types of 1D open channels along the y axis with about 6 × 8 and 9 × 12 Ų dimensions. The solvent accessible space for the desolvated I is 53.4% of the total volume. The 3D structure can also be rationalized as a six-connected (3.4¹¹.5².6) topological network by considering the Tb₂ dinuclear units as six-connected nodes and MFDA ligands as linkers, respectively.     

Facile synthesis of WOx/ZrO2 catalysts using WO3·H2O precipitate as synthetic precursor of active tungsten species

Zirconia-supported tungsten oxide (WO_x/ZrO₂) catalysts were successfully synthesized using a suspension containing amorphous hydrous zirconia precipitates [ZrO_x(OH)_4-2x·yH₂O]_n and tungstate monohydrate (WO₃·H₂O) precipitates. The procedure involved the dissolution of the WO₃·H₂O precipitate during the aging process with the release of oxyanion [WO₄]^2- species, interaction of this species with the surface of the [ZrO_x(OH)_4-2x·yH₂O]_n precipitate and, formation of active WO_x species after thermal treatment. Non-bridging hydroxyl (OH^?) groups present in the [ZrO_x(OH)_4-2x·yH₂O]_n precipitate act as an active agent for the WO₃·H₂O dissolution. N₂ physisorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), temperature-programmed reduction using hydrogen (H₂-TPR), temperature-programmed desorption of ammonia (NH₃-TPD), Fourier-transform infrared (FTIR) spectroscopy of adsorbed pyridine, and Raman spectroscopy were used to elucidate the catalyst structure–performance relationship. The catalytic activity was evaluated for the oxidative desulfurization (ODS) of a model fuel containing dibenzothiophene (DBT). For a fixed WO₃·H₂O content, longer aging times improved the catalyst activity, reaching a maximum when WO₃·H₂O was completely dissolved. The increase in surface area and formation of more active Zr-WO_x clusters and polytungstates are observed for the highest active catalysts. A synergetic effect between local Lewis and Brønsted acid sites seems to have contributed to the observed superior activity. The proposed strategy provides an efficient approach to produce active WO_x/ZrO₂ catalysts and may be applicable for designing other heterogeneous catalytic systems.     

Researches on crystal and molecular structures of nine-coordination mononuclear K[Eu III 2 (Edta)(H2O)3]·3.5H2O and binuclear K4[(HTtha)2]·13.5H2O

The crystal and molecular structures of the K[Eu^III(Edta)(H₂O)₃] 3.5H₂O (I) (H₄Edta = ethylenediaminetetraacetic acid) and K₄[Eu₂^III(HTtha)₂] 13.5H₂O (II) (H₆Ttha = triethylenetetraminehexaacetic acid) complexes have been determined by single-crystal X-ray diffraction analyses. The crystal of I belongs to orthorhombic crystal system and Fdd2 space group. The crystal data are as follows: a = 1.9849(6)nm, b = 3.5598(11)nm, c = 1.2222(4)nm, V = 8.636(5)nm³, Z = 16, M = 596.37, (calcd) = 1.835g/cm³, µ= 3.166mm^–1, and F (000) = 4752. The final R and wR values are 0.0269 and 0.0692 for 2936 (I > 2.0 (I)) reflections and 0.0317 and 0.0708 for all 7284 unique reflections, respectively. The [Eu^III(Edta)(H₂O)₃]^– complex anion has a nine-coordination pseudo-monocapped square antiprismatic structure in which the nine coordinated atom are two N and seven O atoms (four from one Edta ligand and three water molecules). The crystal of II belongs to monoclinic system and P2¹/n space group. The crystal data are as follows: a = 1.1337(3)nm, b = 2.5753(6)nm, c = 2.2138(6) nm, = 102.871(5)°, V = 6.301(3) nm³, Z = 4, M = 1682.33, (calcd) = 1.773g/cm³, = 2.339mm^–1, and F(000) = 3404. The final R and wR are 0.0514 and 0.0906 for 11144 (I> 2.0(I)) reflections and 0.0976 and 0.1068 for all 26 048 unique reflections, respectively. The whole complex molecule is composed of two close parts in which every one has a nine-coordination structure as a distorted monocapped square antiprism. The Ttha ligand in the [Eu ₂^III(HTtha)₂]^4– complex anion coordinates to one central Eu ³⁺ ion with three N atoms and four O atoms and to the other Eu³⁺ ion with two O atoms.From Koordinatsionnaya Khimiya, Vol. 30, No. 12, 2004, pp. 901–909.Original English Text Copyright © 2004 by J. Wang, X. Zhang, Y. Zhang, Y. Wang, X. Liu, Z. Liu.This article was submitted by the authors in English.     

Density functional investigations on the (H2O)n·CCH and (H2O)n·HCC complexes (n=1–3)

The electronic structures and energies of (H₂O)_n·CCH and (H₂O)_n·HCC complexes (n=1–3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2–3 are cyclic structures with homodromic hydrogen-bond chain. The (H₂O)_n·CCH (n=1–3) complexes show increasing stabilities towards CCH- or H₂O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H₂O)_n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H₂O)_n·CCH (n=2,3). Strong interactions between CCH and (H₂O)₂ and (H₂O)₃ clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.     

Synthesis and characteristics of the dioxonium salt based on tartratogermanate acid. Crystal and molecular structure of (H5O2)[(H2O)2Ge(μ-Tart)2Ge(OH)] · 4H2O

Tartratogermanate acid was obtained for the first time as the dioxonium complex (H₅O₂)[(H₂O)₂Ge(??-Tart)₂Ge(OH)] · 4H₂O (I) by the reaction of germanium tetrachloride with D-tartaric acid (H₄Tart) in 85% acetic acid. The complex was characterized by elemental analysis data, thermogravimetry, and IR spectroscopy. X-ray diffraction analysis for I was performed. The crystals are orthorhombic, a = 15.862(3) ?, b = 13.401(3) ?, c = 8.6800(17) ?, V = 1845.1(6) ?³, Z= 4, space group P2₁2₁2, R1= 0.0520 for 5152 reflections with I > 2??(I). Compound I is composed of the dimeric complex anions [(H₂O)₂Ge(??-Tart)₂Ge(OH)]^?, dioxonium cations, and water molecules of crystallization. In the anion, the Ge(1) (CN = 6) and Ge(2) (CN = 5) atoms are linked by two chelating bridging fully deprotonated tartaric acid ligands through two carboxyl (average Ge-O, 1.883(4) and 1.893(4) ?, respectively) and two alcohol (average Ge-O, 1.859(4) and 1.779(4) ?, respectively) oxygen atoms. The coordination polyhedron of Ge (1) is completed to a distorted octahedron by the oxygen atoms of two water molecules (Ge(1)-O(H₂O), 1.933(4) and 1.854(3) ?). The Ge(2) coordination polyhedron is trigonal bipyramid. Its base is formed by two alcohol oxygen atoms of two bridging Tart^4? ligands and the oxygen atom of the terminal hydroxy group (Ge-O, 1.764(4) ?). The axial positions are occupied by the carboxyl oxygen atoms of the Tart^4? ligands (the O(5)Ge(2)O(11), 176.84(16)°). In the crystal, the structural units are combined by hydrogen bonds to a three-dimensional framework.     

In-situ growth hierarchical and superhydrophobic flower-like Cu3(PO4)2·2H2O nanosheets based on copper mesh for efficient oil–water separation

Superhydrophobic porous membranes with interconnected open structures for effective treatment oily wastewater have gradually drawn researchers’ attentions owing to frequent occurrence of organics leakage accidents. In this paper, we successfully fabricated superhydrophobic flower-like Cu₃(PO₄)₂·2H₂O nanosheets on copper mesh surface via in-situ growth strategy and silane coupling agent (A151) hydrophobic modification. Specifically speaking, commercial copper mesh served as substrate and Cu could react with (NH₄)₂S₂O₈ and Na₂HPO₄, forming flower-like micro-nanostructure. As-synthesized materials were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffractometer (XRD). In addition, chemical, mechanical stability and durability of as-prepared materials were also investigated under different condition. The relevant experiment results demonstrated that flower-like Cu₃(PO₄)₂·2H₂O nanosheets successfully grew on copper mesh surface, resulting in the formation of rough structure. Modified copper mesh showed superhydrophobic and superoleophilic properties simultaneously with water contact angle (CA) of 151.24° and oil contact angle of 0°, respectively. The as-prepared materials could be used to separate oily wastewater with high separation efficiency (above 95.0%). The mechanism of oil–water separation was investigated in detail based on positive and negative capillary effect. High separation efficiency, excellent stability and durability of superhydrophobic copper mesh make it one of best promising separation candidates for wastewater treatment.     

Ozone interaction with manganese acetate solution. Formation of H x MnO2·nH2O layers and microtubes based on them

We present the first study of Mn(II) cations interaction with ozone fed onto the air/aqueous manganese acetate solution boundary. In the reaction, the layer of H _x MnO₂·nH₂O of birnessite structure has been formed at the surface. Subsequent ～1–3 μm thick layers drying at air has led to their rolling up to form microtubes with diameter of 20–50 μm and up to 10 mm long.