Hydrothermal synthesis and structure characterization of two six-connected metal–organic frameworks based on the mixed ligands

Two metal–organic frameworks, namely, [Ni₂(BIMB)₂(ndd)₂·H₂O]_n (1) and [Zn₃(ndd)_2.5(μ₃-OH)(1,3-dpp)]_n (2) (H₂ndd = 2,2′-(naphthalene-1,5-diylbis(oxy))diacetic acid, BIMB = 1,4-bis[(1H-imidazol-1-ly)methyl]benzene, 1,3-dpp = 1,3-di(pyridin-4-yl)propane) have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 presents a two-dimensional network with point symbol of (3⁶·4⁶·5³)-hxl topology. Moreover, compound 2 displays a novel 2-fold interpenetrated structure with the point symbol of (4¹²·6³)-pcu topology based on the hexanuclear [Zn₆(CO₂)₁₀(N)₄] unit as a six-connected node. Meanwhile, compound 2 shows good fluorescence property in the solid state at room temperature.     

Hydrothermal synthesis and structural characterization of two inorganic–organic composite sandwich-type tungstogermanates

Two new inorganic–organic hybrid polyoxotungstates [enH₂][C₈N₄H₂₂]₃H₂[Co₄(enH)₂(GeW₉O₃₄)₂] · 6H₂O (1) and [Co(en)₃]₂H₆[Co₄(enH)₂(GeW₉O₃₄)₂] · 14H₂O (2) (en = ethylenediamine) have been synthesized by hydrothermal methods and characterized by IR, TG, XRD, XPS, elemental analysis, and single-crystal X-ray analysis. The polyoxoanion frameworks of the two compounds consist of two classical tetra-Co sandwiched polyoxoanions [Co₄(H₂O)₂(GeW₉O₃₄)₂] in which two organic ligands substitute two water molecules. The tetra-Co clusters in 1 and 2 exhibit the familiar structural type of a β-junction at the sites of metal incorporation. Compound 1 is of interest owing to its C₈N₄H₂₀ ligands resulting from the reaggregation of triethylenetetramine which occurs under 160°C.     

Electrochemical synthesis of stannane–silane and stannane–germane copolymers

Poly(dibutylstannylene-co-dibutylsilylene) and poly(dibutylstannylene-co-dibutylgermylene) were synthesized for the first time, by electrochemical reduction of dibutyldichlorostannane together with dibutyldichlorosilane and dibutyldichlorogermane, respectively, in a one-compartment cell equipped with a platinum cathode and a silver anode, using tetrabutylammonium perchlorate and 1,2-dimethoxyethane as the supporting electrolyte and the solvent, respectively. Most of absorption peaks observed for the copolymers were located between those of polystannylene and polysilylene/polygermylene. A copolymer with relatively high stannane content had a relatively long absorption peak, which is close to that of a homopolymer polydibutylstannylene. A copolymer with a higher stannane content was more sensitive to the moisture in air.     

Hydrothermal synthesis and structures of organic–inorganic hybrid solids based on arsenic-vanadate building blocks

Four novel organic–inorganic hybrid arsenic-vanadate complexes, [Cu(phen)][(As^VO₄)(V^V ₃O₇)(H₂O)] (1), [Cu(en)₂]₂[As₈V₁₄O₄₂(H₂O)]?·?2.5H₂O (2), [M(1,10-phen)₃]₂[As₈V₁₄O₄₂(H₂O)_0.5]?·?0.5H₂O (M?=?Mn, 3, Cd, 4) (1,10-phen?=?1,10-phenanthroline) have been hydrothermally synthesized for the first time and characterized by elemental analyses, XPS spectra, EPR spectra, IR spectra, TG analyses and single crystal X-ray diffraction. The structure of compound 1 consists of arsenic vanadate ribbons coordinated by the [Cu(phen)]²⁺ complex, while compounds 2 to 4 possess a spherical [As₈ ^IIIV₁₄ ^IVO₄₂]^4? cage with H₂O molecules encapsulated. The unexpected preparation 1 and the synthesis of compounds 2 to 4 on the basis of same polyoxoanion structures show that the pH value of the reaction plays a crucial role in controlling the basic architectures.     

Preparation and characterization of a novel organic–inorganic hybrid nanostructure: application in synthesis of spirocompounds

Research on Chemical Intermediates - Immobilization and heterogenization of acidic/basic groups or organic tags on inorganic supports have found many important applications in recent years. In this...     

Thermal behavior of a sol–gel system containing aniline and organic phosphonates

Samples of an organic–inorganic hybrid were prepared by solvolysis and polycondensation in formic acid of tetraethoxysilane and diethylbenzyl phosphonate, simultaneous with the oxidative polymerization of aniline. The thermal behavior of the samples in dynamic air atmosphere and non-isothermal conditions was determined by a coupled thermogravimetric/evolved gas analysis. Two significant thermal events were established: the elimination from the polymeric matrix of low mass molecules, respectively the thermooxidative degradation of the organic part of the matrix. The kinetic analysis was performed with the Flynn-Wall-Ozawa, Friedman and modified Non-Parametric-Kinetic methods. Only the last one allowed an objective analysis of the first process as a process of two simultaneous thermally induced phenomena with the kinetic functions of the type α^m(1 − α)ⁿ.     

Hydrothermal syntheses and structural characterization of two organic–inorganic hybrid compounds based on Lindqvist polyanions

Two organic–inorganic hybrid polyoxometalates {[V₂W₄O₁₉{Cu(2,2′-bipy)₂}₂] · (4,4′-bipy)} _n (1) and [Co(2,2′-bipy)₃][W₆O₁₉] · H₂O (2) (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine), constructed by Lindqvist polyanions and transition metal coordination cations, have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR, UV spectra, thermogravimetric (TG) analyses, X-ray photoelectron spectroscopy (XPS), and single- crystal X-ray diffraction. Compound 1 is a neutral molecule and consists of a di-V^V substituted Lindqvist-type polyanion [V₂W₄O₁₉]^4?, two supporting copper cations [Cu(2,2′-bipy)₂]²⁺ and one free 4,4′-bipy. Neutral molecules of 1 are extended to a 2-D grid-like network by π–π stacking interactions between pyridine groups. The molecular structure of 2 contains one [W₆O₁₉]^2? cluster polyanion and a [Co(2,2′-bipy)₃]²⁺. Inductively coupled plasma (ICP) analysis and XPS spectrum of 1 prove the presence of V^V. TG curves of 1 and 2 indicate two weight loss steps.     

Photochemical synthesis and characterization of hydrogel–silver nanoparticle composites

Research on Chemical Intermediates - Hydrogels were synthesized by grafting polyacrylamide onto dextran using N,N′-methylene-bis-acrylamide as a cross-linker. The hydrogels were converted...     

Low-temperature synthesis and characterization of the Mn–Zn ferrite

Nanocrystalline ferrite with the composition: Mn_0.6Zn_0.4Fe₂O₄ was synthesized by two-stage route: the precipitation of Zn, Mn and Fe hydroxides from sulphates solution and the synthesis of a precursor by the sol–gel auto-combustion method. The ferrite powder obtained from the gel by ashing was sintered under air at a temperature of 720, 1150 and 1300 °C. The composition and morphology of the as-obtained phases were examined by ICP-AES, TG/DTA, XRD, FTIR, SEM and low-temperature nitrogen adsorption (BET). It was found that the spinel phase forms after gel combustion. The nanometric ferrite powder obtained as a result of the combustion is soft-agglomerated. The zinc content in the ferrite during ashing and auto-combustion is lower by about 21 mol% than the assumed one and the final product turn out to be Mn_0.68Zn_0.32Fe₂O₄.     

Application of organic selenides and tellurides in organic synthesis

This paper describes the progress on the synthesis of organic selenides and tellurides and their application in organic synthesis.Low valent selenium and telluronium compounds having high reducing selectivity can be used to form carbon-hydrogen bonds as special reducing reagents.Telluronium ylides can react with aldehydes and ketones by Wittig-type condensation to produce (E)-configuration alkenes stereoselectively.α-Phenylselanyl arsonium ylides were prepared by transyl-idation reaction of arsonium ylides with phenylselanyl halides which can undergo Wittig-type reactions with carbonyl compounds to give (Z)-α-selanyl-α,β-unsaturated compounds with high stereoselectiv-ity.Zirconium,tin,boron,halogen,metal or hetero-atom were introduced in organoselenium and telluronium compounds as new difunctional group reagents.Under transition metal catalysis,the corresponding cross coupling reactions provide new methods of formation of carbon-carbon double bonds,which were used in the stereoselective synthesis of     

Electrochemical synthesis and characterization of polydiphenylamine

Electrochemical oxidation of diphenylamine(DPA)in acetonitrile solution producedan adhesive conducting polydiphenylamine(PDPA)film on the electrode,which exhibited multiplecolour variation in a wide range of potential.The polymer was characterized by cyclic voltam-merry,FTIR and ESR.The results indicate that the electropolymerization of diphenylamine per-forms via the 4,4＇C—C phenyl-phenyl coupling mechanism.FTIR,ESR and conductivity mea-surements for the different states of PDPA show that polydiphenylamine can be reversibly dopedand dedoped either chemically or electrochemically.It is evidenced also that there are paramagneticspecies—polarons in PDPA supposed to be the current carrier.     

Preparation and characterization of inorganic–organic hybrid proton exchange membranes based on phosphorylated PVA and PEG-grafted silica particles

We reported proton-conducting membranes with novel microstructure based on partially phosphorylated poly(vinyl alcohol) (P-PVA) and polyethylene glycol (PEG) grafted silica (PEG-SiO₂) particles. The PEG-SiO₂ particles were synthesized through acid catalyzed hydrolysis and condensation reactions. The membranes were characterized for their mechanical, structural, morphological, and electrical properties by employing tensile test, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), impedance analyzer, respectively. In these membranes, P-PVA acts as the proton source and PEG act as the proton solvent. The PEG-riched phases in the hybrid membrane form continuous ionic conducting pathways and subsequently give high ionic conductivity. The results suggest that the obtained membrane shows good thermal stability, excellent mechanical property and high ionic conductivity, and the low-cost hybrid membrane can be a promising candidate for intermediate temperature fuel cell systems.     

Sol–gel synthesis of sodium and lithium based materials

Sodium and lithium cobaltates are important materials for thermoelectric and battery applications due to their large thermoelectric power and ability to (de-) intercalate the alkali metal. For these applications, phase pure materials with controlled microstructure are required. We report on the sol?Cgel synthesis of sodium- and lithium-based materials by using acetate precursors. The produced Na_2/3CoO₂, Li(Ni_1/3Mn_1/3Co_1/3)O₂, and Li(Ni_1/2Co_1/2)O₂ powders are phase pure with grain sizes below 1???m. X-ray diffraction and energy-dispersive spectral analyses show that the cation stoichiometry is preserved in the lithium-based compounds. Despite the low temperatures, the sodium content is reduced by 1/3 as compared to the initial value. Chemical phases of the investigated powders are formed in the sol?Cgel route at temperatures typically 100?C200?K lower than those used in the conventional solid-state synthesis of these materials. The suggested sol?Cgel synthesis is a low temperature process suited for production of phase pure and homogeneous materials with volatile cations.     

The synthesis of Tempol–phenol derivatives and their protection against radical-induced damage

Stable nitroxides are potential antioxidant drugs. In this study, we have linked nitroxide (Tempol) to phenol with the aim of improving radioprotective activity. The radical scavenging activities of four Tempol–phenol conjugates were evaluated in L-02 and MCF-7 cells survival assays. A differential protection in normal cells as compared to tumor cells was confirmed. In addition, the protective effect of these compounds was demonstrated in a greater increase in peripheral WBC, ANC, AMC, and platelet counts in an in vivo rat model. It might be possible to develop them into a possible agent for radical injury.     

Synthesis and characterization of alternating fluorene–thiophene copolymers bearing ethylene glycol side-chains

Abstract  

New alternating fluorene–thiophene copolymers are introduced bearing polar ethylene glycol-carboxylate functionalities on the thiophene ring to achieve enhanced solubility in polar solvents. Suzuki polycondensation was applied to synthesize a set of three polymers with differing lengths of the ethylene glycol side-chains. The polymers are thermally stable up to temperatures of 300 °C. Solutions of the polymers in CHCl₃ show an absorption maximum at approximately 397 nm and a luminescence maximum of 472 nm in solutions with quantum yield of 30%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels have been determined to be at −5.7 and −2.6 eV, respectively.