Synthesis,characterization, crystal structure,catalytic activity in oxidative bromination,and thermal study of a new oxidovanadium Schiff base complex containing O,N-bidentate Schiff base ligand

A new oxidovanadium(IV) Schiff base complex, VOL₂ (1), HL = 2-{(E)-[2- (bromoethyl)imino]methyl}-6-methoxy phenol, containing ethyl bromide pendant group was synthesized by direct reaction of HL and VO(acac)₂ in the ratio of 2 : 1 in methanol at reflux. The Schiff base ligand and its vanadyl complex were characterized by FT-IR spectra and CHN analysis. Additionally, the Schiff base ligand has been characterized by ¹H NMR spectroscopy. The crystal structure of 1 was also determined by single-crystal X-ray analysis, showing the distorted square-pyramidal N₂O₃ coordination around vanadium(IV). The catalytic activity of 1 was studied in the oxidative bromination of 2-nitrophenol as a model substrate, and different reaction parameters were investigated. The oxidative bromination of some organic compounds in the presence of 1 in optimal conditions showed that it was an effective and selective catalyst in those optimal conditions. Thermogravimetric analysis of 1 showed that it decomposed in two stages. 1 was thermally decomposed in air at 660 °C, and the XRD pattern of the obtained solid showed the formation of the V₂O₅ nanoparticles with average size of 34 nm .     

Simple and Efficient Method for Acetylation of Alcohols,Phenols, Amines,and Thiols Using Anhydrous NiCl2 Under Solvent-Free Conditions

Solvent-free acetylation of alcohols, phenols, amines, and thiols with acetic anhydride (Ac₂O) in the presence of 0.1 mol% (13 mg) anhydrous NiCl₂, an inexpensive and easily available catalyst, is described. Excellent yields, short reaction time, and mild reaction conditions are important features of this method.     

Micellar Catalysis on the Redox Reaction of Ascorbic Acid-Vanadium(V) System

Stoichiometry of the redox reaction of vanadium(V) by ascorbic acid (H₂A) has been experimentally determined to be H₂A + 2V(V) → A + 2V(IV) + 2H ⁺ . Evidence of induced polymerization of acrylonitrile and the reduction of mercuric chloride indicates that a free-radical mechanism operates during the course of reaction. Vanadium(V) is only reduced to vanadium(IV). The kinetics of this redox reaction have been investigated spectrophotometrically at 35°C in acidic media of H₂SO₄. In this kinetic study we have observed the nature of vanadium(V)-H₂A interaction in presence of anionic surfactant of SDS. In V(V)-H₂A system, the addition of anionic surfactant (SDS) enhanced the reaction rate and shows catalytic effect. This trend was explained by the incorporation/solubilization of vanadium(V) and ascorbic acid in the Stern layer.     

Rietveld refinement of sol–gel Na<Subscript>2</Subscript>Ti<Subscript>6</Subscript>O<Subscript>13</Subscript> and its photocatalytic performance on the degradation of methylene blue

We have refined single crystals of Na₂Ti₆O₁₃ through the X-ray Rietveld method. The synthesis of the Na₂Ti₆O₁₃ was carried out by sol–gel method at 70 °C, and the obtained gel was heat treated at different temperatures. Through different analytical techniques such as X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), Infrared Spectroscopy (FTIR), and Thermal Analysis (DTA/TGA), it was determined that Na₂Ti₆O₁₃ can be prepared at low temperature (750 °C) by sol–gel method. The product crystallizes in rectangular shape micro-fibers, free of impurities. Rietveld refinement was performed using X-ray diffraction technique taking as basis a monoclinic cell with space group C2/m. The following refined parameters were obtained: a = 15.095(7) Å, b = 3.745(3) Å, c = 9.174(1) Å, β = 99.01. Additionally, Na₂Ti₆O₁₃ was tested as photocatalysts on the degradation of methylene blue (MB) under UV light. The degradation reaction follows a first order reaction model with kinetic parameters k = 0.0089 min^?1, and t _1/2 = 78 min.     

Preparation,Characteristics, and Photocatalytic Tests of Fe-Doped TiO2 Films Prepared by a Sol-Gel Drain Coating via Homemade Devices

Anatase Fe-doped TiO₂ films, with the rang of iron to titanium (Fe(NO₃)₃ · 9H₂O:Ti(OC₄H₉)₄)) atomic ratios (R _Fe/Ti ) from nominal 0 to 20%, are prepared by a sol-gel drain coating via homemade devices, and the hydrolysis reaction to derive sol is suppressed by adding an new agglomerating agent acetylacetic ether (EAcAc) to the system. The films are characterized by using thermogravimetry and differential thermal analysis (TG-DTA), x-ray diffraction (XRD), ultraviolet (UV)–visible absorbance spectra (UV–vis), and scanning electron microscope (SEM), together with energy-dispersive x-ray spectroscopy (EDX). Furthermore, the photocatalytic activities are measured by photodegrading rhodamine B (RhB) in a cylindrical Pyrex reactor, the experimental details demonstrate that the Fe-doped TiO₂ films (R _Fe/Ti  = 3.0%) show the most excellent photocatalytic perfomances, which is good accordance with UV-vis spectra.     

Iron(III), nickel(II) and zinc(II) complexes based on acetophenone-S-methyl-thiosemicarbazone: synthesis,characterization, thermogravimetry,and a structural study

New complexes, [Fe(L)Cl], [Ni(L)], and [Zn(L)C₂H₅OH] (1–3), were synthesized by template reaction of 2-hydroxy-acetophenone-S-methyl-thiosemicarbazone with 2-hydroxy-benzaldehyde. The compounds were characterized by elemental analysis, magnetic measurements, FT-IR, ¹H NMR, UV–visible, and ESI–MS spectra. In these complexes, the ligand is coordinated to the metal ion as dinegatively charged tetradentate chelating agents via the N₂O₂ donor set. The iron(III) and zinc(II) complexes exhibit square pyramidal geometry whereas the nickel(II) complex has a square planar geometry. The crystal structure of 1, determined by X-ray diffraction method, indicates that 1 crystallizes in the monoclinic space group P21/c with Z = 4. Thermal decompositions of the compounds have been investigated using TGA in air.     

NMR and kinetic studies of the interactions of [Au(cis-DACH)Cl2]Cl and [Au(cis-DACH)2]Cl3 with potassium cyanide in aqueous solution

The interactions of [Au(cis-DACH)Cl₂]Cl and [Au(cis-DACH)₂]Cl₃ [where cis-DACH is cis-1,2-diaminocyclohexane] with enriched KCN were carried out in CD₃OD and D₂O, respectively. The reaction pathways of these complexes were studied by ¹H, ¹³C, ¹⁵N NMR, UV spectrophotometry, and electrochemistry. The kinetic data for the reaction of cyanide with [Au(cis-DACH)₂]Cl₃ are k = 18 M^?1s^?1, ?H^≠ = 11 kJ M^?1, ?S^≠ = ?185 JK^?1 M^?1, and E_a = 13 kJ M^?1 with square wave voltammetric (SWV) peak +1.35 V, whereas the kinetic data for the reaction of cyanide ion with [Au(cis-DACH)Cl₂]Cl are k = 148 M^?1s^?1, ?H^≠ = 39 kJM^?1, ?S^≠ = ?80 JK^-1 M^?1, and E_a = 42 kJM^?1 along with SWV peak +0.82 V, indicating much higher reactivity of [Au(cis-DACH)Cl₂]Cl toward cyanide than [Au(cis-DACH)₂]Cl₃. The interaction of these complexes with potassium cyanide resulted in an unstable [Au(¹³CN)₄]^? species which readily underwent reductive elimination reaction to generate [Au(¹³CN)₂]^? and cyanogen.     

Synthesis,structure, and characterizations of a new antiferromagnetic manganese(II) dichloro-bridged 1-D polymer decorated by 5-amino-1-H-tetrazole

[Mn(5-ATZ)₂Cl₂]_n (1) (5-ATZ – 5-amino-1-H-tetrazole) was synthesized from the reaction of 5-ATZ and manganese(II) chloride and isolated by solution evaporation at room temperature. 1 was characterized by elemental analysis, X-ray crystallography, infrared, and EPR spectroscopy as well as magnetic measurements. In the crystal structure, [Mn(5-ATZ)₂Cl₂] units are linked by double μ₂-bridging chlorides to form 1-D chains parallel to the a-axis. The Mn sphere approximates to octahedral with the metal coordinated by four chlorides in the equatorial plane and two 5-ATZ molecules, bound through their ring nitrogens, in axial positions. The intramolecular N–H···Cl hydrogen bond between the 5-ATZ amino group and the adjacent coordinated Cl^? stabilizes the chain. N–H···N hydrogen bonds between adjacent chains form a 3-D supramolecular framework. No hyperfine coupling to the Mn nuclei (I = 5/2) is observed in the powdered EPR spectrum of 1 at 77 K. The frozen solution EPR spectrum provides evidence of the mononuclearity of 1 in methanol. The magnetic properties have been analyzed using the Hamiltonian H = –J∑S_i · S_i+1 with J = ?1.38(3) cm^?1 and g = 2.00(1). A small value of the exchange parameter is typical for 1-D six-coordinate bis(μ₂-chloro) Mn(II) polymers.     

Syntheses,crystal structures,and magnetic properties of a series of Fe2Ln complexes

A family of phenoxo-bridged heterometallic Schiff base trinuclear complexes, [Fe₂LnL₂(C₃H₇COO)(H₂O)]·CH₃OH·CH₃CN·H₂O (Ln = Sm, 1; Gd, 2; Tb, 3; Dy, 4) is reported. Those complexes were afforded by “one-pot” reaction of a polydentate Schiff base ligand 2-hydroxy-3-methoxy-phenylsalicylaldimine (H₂L) with Fe(NO₃)₃·9H₂O, Ln(NO₃)₃·6H₂O and sodium butyrate (C₃H₇COONa) in a mixture of methanol and acetonitrile in the presence of triethylamine as a base. Single-crystal X-ray diffraction analysis reveals that the structures of the four complexes are isomorphic. In each complex, two anionic [FeL₂]^? units coordinate to the central lanthanide ion as a tetradentate ligand using its four phenoxo oxygens, forming a two-blade propeller-like molecular shape. Magnetic properties of 1–4 were investigated using variable temperature magnetic susceptibility, and weak ferromagnetic exchange between the Fe^III and Ln^III ions has been established for the Gd derivative. The Tb and Dy complexes show no evidence of slow relaxation behavior above 2.0 K.     

Conformational stability, r 0 structural parameters, barriers to internal rotation, ab initio calculations, and vibrational assignment for 2,2-difluoroethanol

The infrared spectra (4,000–30 cm^?1) of the gas and solid and the Raman spectrum of liquid 2,2-difluoroethanol as well as variable temperature infrared spectra of krypton/xenon solutions have been recorded. From all these data, two (Gg and Tg) out of the five possible stable conformers have been confidently identified. The order of the stabilities has been predicted to be Gg > Tg > Gt > Gg′ > Tt by utilizing ab initio MP2 (full) and DFT (B3LYP method) calculations, where the first indicator (capital letter) is in reference to rotation around the C–C bond (G = gauche or T = trans) and the second one (small letter) refers to the orientation of the hydroxyl group. The percentage of the minor conformer Tg, at ambient temperature, is estimated to be (16 ± 3%). The optimized geometries, fundamental frequencies, infrared intensities, Raman activities, and depolarization values as well as centrifugal distortion constants have been obtained from ab initio and density functional theory calculations by utilizing a variety of basis sets as well as those with diffuse functions. By utilizing the previously reported microwave rotational constants for two isotopomers of the Gg conformer combined with ab initio MP2(full)/6-311+G(d,p) predicted structural values, adjusted r ₀ parameters have been obtained. The determined heavy atom distances (Å) for the Gg conformer are: C₁–C₂ = 1.510(3), C₂–F₄ = 1.371(3), C₂–F₅ = 1.362(3), C₁–O₃ = 1.412(3) Å and angles ∠O₃C₁C₂ = 111.0(5), ∠F₄C₂C₁ = 108.8(5), ∠F₅C₂C₁ = 109.8(5), τF₄C₂C₁O₃ = 63.5(5), τF₅C₂C₁O₃ = 179.1(5)°. Barriers of internal rotation have been obtained and vibrational assignments for the Gg and Tg conformers are given. The five predicted centrifugal distortion constants compared to the experimental values are in reasonable agreement except for ?_K, which appears to be in error. The results are discussed and the structural parameters compared to the corresponding ones for 2-fluoroethanol and 2,2,2-trifluoroethanol where those for the latter molecule have been redetermined. The currently determined heavy atom parameters are quite different from the earlier assumed values, which led to poor values of the six adjusted parameters.     

Multicomponent Domino Process for the Synthesis of Some Novel Benzo[a]chromenophenazine Fused Ring Systems Using H2SO4, Phosphotungstic Acid,and [NMP]H2PO4

Efficient, mild, and quantitative procedures for the synthesis of functionalized benzo[c]chromeno[2,3-a]phenazine derivatives by one-pot, four-component condensation of 2-hydroxynaphthalene-1,4-dione, 1,2-phenylenediamines, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds have been developed using catalytic amounts of H₂SO₄ and phosphotungstic acid in EtOH/H₂O (1:1) under reflux and also with [NMP]H₂PO₄, which acts as catalyst and medium at 80 °C. The reaction avoids tedious workup procedure due to the direct precipitation of products from the reaction medium. The present finding provides promising synthetic strategies for the synthesis of libraries with functional group diversity.     

Modification,characterization and peroxidase-mimetic properties of calcined product of a cobalt compound

One-pot solvothermal treatment of Co(NO₃)₂·6H₂O, H₂L (5-(3-methyl-5-(pyridin-4-yl)-4H-1,2,4-triazol-4-yl) isophthalic acid), and 4,4′-bipyridine (4,4′-bipy) in H₂O/DMF (V/V = 1?:?1) yielded a cobalt-organic chain, [Co(L)(O)(H₂O)₂]_n·1.25nH₂O (1). Compound 1 as raw materials was calcined to obtain Co₃O₄, which could be confirmed by PXRD and SEM. Via the modification, Co₃O₄@SiO₂-NH₂ and Co₃O₄@SiO₂-NH₂-FA samples could be obtained. Compared to Co₃O₄@SiO₂-NH₂, Co₃O₄@SiO₂-NH₂-FA seems to have better peroxidase-mimetic properties. UV–vis results showed that optimal conditions of peroxidase-mimetic experiments were at 50°C in sodium acetate-acetic acid buffer (pH 3.6, 0.2 M), when the concentration of tetramethylbenzidine (TMB) was 0.2 mM. A concentration-dependent manner was shown between the concentration of glucose and absorbance in the measurement experiments for glucose.     

KHSO4 · H2O/SiO2‐Catalyzed,One‐Pot,Solvent‐Free Synthesis of Pyrazolines,Tetrahydrocarbozoles and Indoles using Microwave Irradiation

A new high‐yielding, operationally simple, solvent‐free, and mild method for preparation of pyrazolines, tetrahydrocarbazoles, and indoles has been developed using KHSO₄ · H₂O impregnated on SiO₂. The reactions have been probed under microwave irradiation (MWI), and ultrasonic and thermal conditions, employing different solid supports. The data revealed that KHSO₄ · H₂O impregnated on SiO₂ under MWI provides the best yields in a shorter time under solvent‐free reaction conditions.     

Absorption,desorption and interaction of SO2 with the binary system tetraethylene glycol + dimethyl sulfoxide

The gas-liquid equilibrium (GLE) data were determined for the mixture SO₂ + N₂ in the binary system of tetraethylene glycol (TeEG) + dimethyl sulfoxide (DMSO) at T = 298.15–313.15 K and p = 123.15 kPa with the SO₂ partial pressures of 0.4–150 Pa. From GLE data, Henry’s law constants (HLCs) were obtained. When the SO₂ concentration in the gas phase was designed at y_SO2 = 500 ppmv, the SO₂ solubility in the binary system is located in a minimum of 9.36 mol m^?3 in TeEG and a maximum of 80.34 mol m^?3 in DMSO. The SO₂ absorption process was reversible from the five absorption–desorption cycles, and the solvents could repeat utilisation without obvious loss of absorption capacity and the homologous SO₂ desorption efficiency was nearby 98.7%. Furthermore, the spectral consequences illustrated that H-bonding was formed among TeEG, DMSO and SO₂.     

KAl(SO4)2 · 12H2O as a Recyclable Lewis Acid Catalyst for Synthesis of Some Amidoalkyl Naphthols Under Solvent-Free Conditions

A general and practical one-pot synthesis of amidoalkyl naphthols derivatives using KAl(SO₄)₂ · 12H₂O as catalyst is described. This method provides several advantages such as short reaction times, good yields, and simple workup procedure.     

Syntheses,crystal structures,and electrochemical studies of dinuclear coordination compounds with the Fe2(CO)6 core

Reaction of 2-C₅H₄ NCOSPh, generated from 2-C₅H₄NCO₂H and PhSH in the presence of DCC, with Fe₃(CO)₁₂ affords (μ-κ²C,N-2-C₅H₄N)(μ-PhS)Fe₂(CO)₆ (1) and (μ-PhS)₂Fe₂(CO)₆ (2). Reaction of (NC)₂C=C(SMe)₂, formed from NCCH₂CN, CS₂, and MeI in the presence of NaOH, with Fe₃(CO)₁₂ provides (μ-κ²C,S-(NC)₂C=CSMe)(μ-MeS)Fe₂(CO)₆ (3) and (μ-MeS)₂Fe₂(CO)₆ (4). All complexes have been fully characterized by EA, IR, ¹H NMR, and ¹³C NMR spectroscopy and structurally determined by X-ray crystallography. In 1 and 3, the group attached to the bridging S is at the equatorial position. In 2, two phenyl groups are at equatorial positions. Two isomers of 4, ae-4 and ee-4, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-4 and ee-4 is ?2.17 kcal mol^?1 in THF and ?2.29 kcal mol^?1 in benzene, and the isomerization barrier between ae-4 and ee-4 is 14.92 kcal mol^?1 in THF and 16.84 kcal mol^?1 in benzene. All these results suggest that ae-4 is more stable than ee-4 in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of 1 and 3 demonstrate that using HOAc as a proton source 1 and 3 can catalyze H₂ production.     

Hierarchically Structure SnO2/ZnO Nanocomposites: Preparation,Growth Mechanism and Gas Sensing Property

SnO₂/ZnO nanocomposite was synthesized from mixed ethanol and water systems and the ethanol-sensing properties of sensors based on SnO₂/ZnO were investigated. The structure and morphology of the products was characterized by x-ray diffraction (XRD) and a field emission scanning electron microscope (FE-SEM). The results showed that the diameter of the liked pine needle SnO₂ was about 40 nm with a length about 300 nm, which are uniformly dispersed on the surface of the ZnO nanosheets. The growth process of the SnO₂/ZnO nanocomposite was discussed. The results of gas sensing properties of SnO₂/ZnO nanocomposite sensor showed high and quick response to ethanol vapor at 5.0 v. This sensor showed the advantages of high selectivity, strong stability, and prompt response/recovery characteristics in detecting ethanol vapor at 5.0 v.     

Simple and Efficient System for the α-Bromination of a β-Ketoester by Using N-Bromosuccinimide in the Presence of Silica-Supported NaHCO3 as the Heterogeneous Catalyst: An Environmentally Benevolent Approach

Selective and efficient α-bromination of β-ketoesters and cyclic and acyclic ketones is achieved by reaction with N-bromosuccinimide (NBS) catalyzed by silica-supported sodium bicarbonate (NaHCO₃ · SiO₂) under mild reaction conditions and with short reaction times. With 100% selectivity with all substrates, after 45 min at room temperature (20 ± 2 °C), conversions for ethylacetoacetate were 67% and for acetophenone, cyclohexanone, and cycloheptanone were 58, 50, and 55%, respectively. Acetyl acetone recorded 65% conversion with 100% selectivity. Although cyclopentanone and toluene had only 20% conversion, both reactions showed 100% selectivity toward α-bromination. The catalysts exhibit activity and reusability.     

Chemiluminescent Determination of Vitamin B12 Using Charge Coupled Device (CCD)

A method was developed for the determination of vitamin B₁₂ based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B₁₂ was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction.

The optima experimental conditions were established: 8.0 m mol L^?1 luminol in a 0.075 mol L^?1 carbonate buffer (pH 10.0) and 0.15 mol L^?1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s^?1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L^?1 (r² = 0.9990), with a detection limit of 0.42 µ g L^?1. The proposed method was successfully applied to the determination of vitamin B₁₂ in pharmaceuticals.