Ligand-free C–N bond formation in aqueous medium using a reusable Cu–Mn bimetallic catalyst

A general ligand-free protocol has been described for the recyclable and reusable Cu–Mn catalyzed C–N bond forming cross coupling reaction of arylboronic acids with various amines to form N-arylated amine products in aqueous medium affording excellent yields under ambient conditions, in 3–4 h.     

Synthesis of an Ag–ZnO nanocomposite catalyst for visible light-assisted degradation of a textile dye in aqueous solution

The photocatalytic activity of silver-deposited ZnO in the photodegradation of methyl orange (MO) was investigated. The as-prepared photocatalysts were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The results showed that the silver-deposited ZnO had a visible light plasmon absorption band. The photocatalytic degradation experiment revealed that the catalytic efficiency of the Ag–ZnO composite in the degradation of MO was greater than that of pure ZnO samples. This study shows that the degradation process is dominated by the Ag–ZnO photocatalytic system, complying with a pseudo-first-order rate law. Under the experimental conditions, approximately 65.0% dye removal was achieved within 100 min.     

Colorimetric sensing of cyanide anion in aqueous media with a fluorescein–spiropyran conjugate

A fluorescein–spiropyran conjugate (2) behaves as a receptor for colorimetric sensing of cyanide anion (CN^?) in aqueous media under irradiation of UV light. The compound 2, which exists as a spirocycle-closed (SP) form in the dark condition, is isomerized to the spirocycle-opened merocyanine (MC) form upon irradiation of UV light and shows absorption bands at 467 and 568 nm. Addition of CN^? to the solution leads to a decrease in these bands and an appearance of new absorption band at 512 nm, via a nucleophilic interaction between CN^? and the spirocarbon of MC form. This absorption change occurs selectively with CN^? and enables ratiometric quantification of CN^? by absorption analysis.     

Photocatalytic performance of combustion synthesized β-Ga2O3 for the degradation of tri-n-butyl phosphate in aqueous solution

Nanostructures of β-Ga₂O₃ were prepared by solution combustion route using urea as the fuel. Transmission electron microscopic measurements and powder X-ray diffraction measurements confirmed the crystalline nature of β-Ga₂O₃ with particle size in the range of 10–15 nm. Surface area measurements indicated that the synthesized semiconductor catalyst had a specific surface area of 30 m²/g. In this work, photocatalytic degradation studies of tri-n-butyl phosphate using nano sized β-Ga₂O₃ is presented. A cylindrical photoreactor was used for the degradation studies and gas chromatographic estimation was adopted to follow the extent of degradation. Complete degradation of tributyl phosphate could be achieved in less than 40 min using 10 mg of photocatalyst and 0.5 mL of H₂O₂ for 1000 mL of 400 ppm TBP. Degradation of TBP was found to follow pseudo first order kinetics and the rate of TBP degradation was found to be superior for β-Ga₂O₃ photocatalyst compared to P-25 TiO₂.     

An in situ generated CuI/metformin complex as a novel and efficient catalyst for C–N and C–O cross-coupling reactions

An in situ generated complex of copper(I) and a biguanide, namely metformin, was found to be a highly efficient homogeneous catalyst in N/O-arylation reactions. The O-arylation of substituted phenols with various aryl iodides and bromides was also achieved using this copper catalyst to afford diaryl ethers in good to excellent yields in DMF. This heterogeneous copper catalyst also promotes the N-arylation of imidazole with a variety of aryl halides (Cl, Br, I) in acetonitrile.     

Irradiation of Fe–Mn@SiO2 with microwave energy enhanced its Fenton-like catalytic activity for the degradation of methylene blue

Research on Chemical Intermediates - The application of microwave energy in the synthesis of catalytic materials has been indicated to induce desirable effects that lead to improved activity....     

Highly effective activation of aryl chlorides for Suzuki coupling in aqueous media using a ferrocene-based Pd(II)–diimine catalyst

The Suzuki coupling of aryl chlorides with boronic acids using a ferrocene-containing Pd(II)–diimine complex as catalyst, in aqueous media, under microwave heating is reported. A small amount of the catalyst (0.1%) was found to be highly effective for coupling unactivated aryl chlorides with boronic acids to form sterically hindered ortho-substituted biaryls. The same catalyst also enabled the coupling of aryl bromides and iodides with various boronic acids in very high yields. The catalyst is air stable and the catalytic reaction can be completed in 15 min.     

Thermoanalytical and dilatometric studies of the Al2O3–Cu–Mo hybrid composite

Journal of Thermal Analysis and Calorimetry - The present research is focused on the characterization of the composites from Al2O3–Cu–Mo system. The composites were prepared by slip...     

Mono- and dinuclear cyclopalladates as catalysts for Suzuki–Miyaura cross-coupling reactions in predominantly aqueous media

Suzuki–Miyaura cross-coupling reactions of aryl halides with arylboronic acids were performed in predominantly aqueous media employing two mono- and two dinuclear cyclopalladated complexes as catalysts. These complexes are [Pd(HL)Cl] (I), [Pd(L)(PPh₃)] (II), [Pd₂(μ-dppb)(L)₂] (III) and [Pd₂(μ-dppf)(L)₂] (IV); where H₂L, dppb and dppf represent 4-methoxy-N′-(mesitylidene)benzohydrazide, 1,4-bis(diphenylphosphino)butane and 1,1′-bis(diphenylphosphino)ferrocene, respectively. The reactions were conducted using potassium carbonate as base in presence of tetrabutylammonium bromide (TBAB) at 70/90 °C in dimethylformamide–water (1:20) mixture. Among the four catalysts used, the dinuclear complex IV turned out to be the most effective and afforded moderate to excellent yields with broad substrate scope.     

Preparation of Mn2O3 catalyst with core–shell structure via spray pyrolysis assisted with glucose

A novel core–shell Mn₂O₃ catalyst is obtained by facile spray pyrolysis assisted with glucose acting as a structure-directing agent. The detail characterizations include X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption isotherms, and the thermogravimetric method (TG/DTA). In the probe test of the aqueous degradation of methylene blue (MB), the high catalytic peroxidization activity of core–shell Mn₂O₃ catalyst, compared to the commercial Mn₂O₃, is attributed to the high crystallization of α-Mn₂O₃, the large surface area that resulted from the core–shell structure with porous architecture, and the special core–shell structure that acted as a micro-reactor.     

Stannous oxalate as a novel catalyst for the synthesis of polytrimethylene terephthalate

Stannous oxalate was prepared efficiently and characterized by XRD and FT-IR. It exhibited higher catalytic activity and had profitable effect than tetrabutyl titanate and stannous octoate for the synthesis of polytrimethylene terephthalate (PTT) via esterification-route. Over this catalyst, the degree of esterification of pure terephthalic acid was up to 94.4% at 260°C after 1.5 h, while the intrinsic viscosity and content of terminal carboxyl groups of the corresponding PTT polyester, polymerized at 260°C, 60 Pa for 2 h, was 0.8950 dL/g and 15 mol/t, respectively. Stannous oxalate was a promising catalyst for the synthesis of PTT polyester.     

Nano-Fe3O4@SiO2–TiCl3 as a novel nano-magnetic catalyst for the synthesis of 4H-pyrimido[2,1-b]benzothiazoles

Research on Chemical Intermediates - Fe3O4@SiO2–TiCl3 NPs, a novel core shell catalyst, was synthesized via preparing Fe3O4@SiO2 as a magnetic support followed by treatment with titanium...     

Synthesis,characterization and application of a novel nanorod-structured organic–inorganic hybrid material as an efficient catalyst for the preparation of aminouracil derivatives

Research on Chemical Intermediates - In this work, a novel nanorod-structured organic–inorganic hybrid material namely nanorod-[SiO2-Pr-Im-SO3H][TFA] (N-[SPIS][TFA]) has been synthesized, and...     

A Pd(II) complex of a β-cyclodextrin-based polydentate ligand: an efficient catalyst for the Suzuki reaction in aqueous media

Molecular assembly has become a promising strategy for designing new polydentate ligands. But very often such ligands and their complexes are sparingly soluble in aqueous phase due to their intrinsic hydrophobic character. Pd(II) complexes are good homogeneous catalysts but their poor solubility in aqueous phase may limit their catalytic efficacy in the universal green solvent water. However, solubility related challenges especially in aqueous phase can be mitigated through the formation of inclusion complexes by exploiting the hydrophobic nature of the β-cyclodextrin (β-CD) cavity. Hence, an ionic liquid ChCD (1) was synthesized from β-CD and Choline bromide (ChBr). Next a supramolecular N, N^′, O-tridentate ligand 1?2 (3) was synthesized by the inclusion of 2,6-diaminopyridine (2) in the hydrophobic β-CD cavity of the ionic liquid ChCD (1) and was well characterized by elemental analysis, UV-visible, FTIR, ¹H NMR spectroscopy, etc. The stoichiometry of the inclusion complex 1?2 (3) was found to be 1:1 based on UV-visible spectrophotometric study. A new air stable, highly water soluble Pd²⁺-complex [κ³-N, N^′, O-Pd(1?2)H₂O]OAc (4) was then synthesized from the supramolecular ligand (3) with 1:1 stoichiometry and used as a catalyst for Suzuki cross-coupling reactions in water at ambient temperature with good to excellent yields. The catalyst can be removed and recycled. Additionally, the use of non-toxic solvent water makes the methodology green, sustainable, and economically viable.     

Photocatalytic performance of combustion-synthesized β and γ-Ga2O3 in the degradation of 1,4-dioxane in aqueous solution

Nanostructures of β and γ-Ga₂O₃ were prepared by the solution combustion route using urea as fuel. The synthesized nano photocatalysts were characterized by use of XRD, FT-IR, BET, TEM, TGA–DTA, DRS, and Raman spectroscopy. XRD and TEM investigations confirmed the nanostructures; particle size was in the range 3–5 nm for γ-Ga₂O₃ and 40–50 nm for β-Ga₂O₃. The specific surface area of γ-Ga₂O₃ was 91 m² g^?1 and that of β-Ga₂O₃ was 24.3 m² g^?1. The polymorphs of gallium oxide were used as photocatalysts for decomposition of 1,000 mg/l 1,4-dioxane. More than 90 % of the 1,4-dioxane could be degraded in less than 180 min by use of 10 mg/l photocatalyst + 0.5 ml H₂O₂. The efficiency of photocatalytic degradation of 1,4-dioxane by the synthesized photocatalysts was compared with that of P-25 TiO₂ and followed the order γ-Ga₂O₃ ≥ β-Ga₂O₃ > P-25 TiO₂. The degradation was found to follow pseudo first-order kinetics.     

Synthesis and characterization of Fe3O4@SiO2–polymer-imid–Pd magnetic porous nanospheres and their application as a novel recyclable catalyst for Sonogashira–Hagihara coupling reactions

We demonstrate herein the modification of magnetic nanoparticles and their use as a magnetic nanocatalyst in direct coupling reactions of aryl halides with terminal alkynes. Magnetite particles were prepared by simple co-precipitation method in aqueous medium, and then Fe₃O₄@ SiO₂ nanosphere was synthesized by using nano-Fe₃O₄ as the core, TEOS as the silica source and PVA as the surfactant. Fe₃O₄@SiO₂ was coated with polymeric N-heterocyclic carbene/Pd. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, field emission scanning electron microscopy, dynamic light scattering, thermogravimetric analysis, vibration sample magnetometer and N₂ adsorption–desorption isotherm analysis. Poly (N-vinyl imidazole) functionalized Fe₃O₄@SiO₂ nanoparticle was found to be an efficient nanocatalyst in Sonogashira–Hagihara cross-coupling reactions. The nanocatalyst can be easily recovered by a magnetic field and reused for six runs without appreciable loss of its catalytic activity.     

Oxidative degradation of dipeptide (glycyl–glycine) by water-soluble colloidal manganese dioxide in the aqueous and micellar media

The kinetics of the oxidative degradation of dipeptide glycyl–glycine (Gly-Gly) by water-soluble colloidal MnO₂ in acidic medium has been studied by employing visible spectrophotometer in the aqueous and micellar media at 35 °C. To obtain the rate constants as functions of [Gly-Gly], [MnO₂] and [HClO₄], pseudo-first-order conditions were maintained in each kinetic run. The first-order-rate is observed with respect to [MnO₂], whereas fractional-order-rates are determined in both [Gly-Gly] and [HClO₄]. The addition of sodium pyrophosphate and sodium fluoride has composite effects (catalytic and inhibition). The reaction proceeds through the fast adsorption of Gly-Gly on the surface of the colloidal MnO₂. The observed results are discussed in terms of Michaelis–Menten/Langmuir–Hinshelwood model. The Arrhenius and Eyring equations are found valid for the reaction over a range of temperatures and different activation parameters have been evaluated. A probable reaction mechanism, in agreement with the observed kinetic results, has been proposed and discussed. The influence of changes in the surfactant concentrations on the observed rate constant is also investigated and the reaction followed the same type of kinetic behavior in micellar media. The pseudo-first-order rate constant (k_ψ) is found to increase about two-fold with increase in [TX-100]. The catalytic effect of nonionic surfactant TX-100 is explained in terms of the mathematical model proposed by Tuncay et al.     

Improved electrochemical performance of sol–gel method prepared Na4Mn9O18 in aqueous hybrid Na-ion supercapacitor

The rod-like Na₄Mn₉O₁₈ material was prepared by sol–gel method and compared with a similar material produced by solid-state method. Their electrochemical properties were examined in aqueous sodium-ion electrolyte cells. The resulting Na₄Mn₉O₁₈ materials were characterized by SEM, TGA, and XRD techniques. The analysis shows that the rod-like Na₄Mn₉O₁₈ has a small particle diameter ranging from 0.2 to 1 μm. The electrochemical performance was characterized by cyclic voltammetry and galvanostatic charge–discharge test in aqueous Na-ion cells with active carbon (AC) as counter electrode. The Na₄Mn₉O₁₈ materials prepared at 800 °C show a high specific capacity of about 200 F g^?1 at a current density of 200 mA g^?1. The Na₄Mn₉O₁₈/Na₂SO₄/AC Na-ion hybrid supercapacitor exhibits excellent cycle performance through 4,000 cycles with 84 % capacity remaining at 500 mA g^?1 charge–discharge current density (an 18 C rate).     

Preparation and application of a novel orotic acid chelating resin for removal of Cu(Ⅱ) in aqueous solutions

A novel chelating resin OABA,capable of removing Cu(Ⅱ) from aqueous solution,was synthesized via the reaction of macroporous chloromethylated PS-DVB copolymer beads with orotic acid.The elemental analysis(EA),Fourier transform infrared spectroscopy(FT-IR),and scanning electron microscopy microscope-energy dispersive X-ray spectroscopy(SEM-EDS) were used in the characterization of the synthesized chelating resin.Multiple,static batch adsorption experiments were conducted at different initial concentrations and temperatures.OABA showed good adsorption capacity for Cu(Ⅱ) and the equilibrium data could be well matched with the Freundlich isotherm model.Coexisting sodium chloride and calcium chloride in solutions favored the Cu(Ⅱ) adsorption.Moreover,the desorption process of Cu(Ⅱ) was tested and over 90%regeneration efficiency for the spent OABA was achieved at ammonia concentrations ranging from 1.0%to 2.0%.The results suggested that OABA would be a potential alternative adsorbent for Cu(Ⅱ),even with other heavy metal ion treatments of wastewater.