Enantioselective phase transfer alkylation using orthopalladated complex in chiral ionic liquid

The optically active orthopalladated phenanthrylamine phase transfer catalyst has been produced and explored for asymmetric glycine alkylation. The catalyst (10 mol%) in toluene/chloroform with 50% aqueous KOH (25 °C) promoted benzylation of benzophenone imine tert-butyl glycine. The product was obtained in 85% yield and 15% enantiomeric excess (ee). Addition of the chiral ionic liquid N,N-dimethyl ephedrinium bis(trifluoromethansulfon)imidate enhanced reactivity and selectivity for PTC glycine alkylation. It appears that the chiral ionic liquid has a cooperative effect to boost the ee content of an asymmetric reaction.     

Decomposition of tert-butyl hydroperoxide into tert-butyl alcohol and O2 catalyzed by birnessite-type manganese oxides: Kinetics and activity

Birnessite-type manganese oxides (M-OL-1s, M = K, Mg, Fe, Ni and Cu) are first reported to efficiently catalyze the decomposition of tert-butyl hydroperoxide (TBHP) into tert-butyl alcohol (TBA) and O₂ with a 100% selectivity towards TBA under heterogeneous conditions. The same form of overall second-order kinetic equations is fitted out for the M-OL-1s and explained by the proposed mechanism. Life tests and XRD analyses demonstrate no losses in both the activity and the birnessite-type structure after the reaction.     

Highly efficient oxidation of diphenylmethane to benzophenone employing a novel ruthenium catalyst with tert-butylhydroperoxide under mild conditions

The ruthenium complex Ru(bpbp)(pydic) (bpbp = 2,6-bis(1-phenylbenzimidazol-2-yl), pydic = pyridine-2,6-dicarboxy acid) has been synthesized and tested in the selective oxidation of diphenylmethane to benzophenone utilizing tert-butylhydroperoxide as the terminal oxidant. The influence of various reaction parameters such as temperature, catalyst amount and nature of solvent on the activity and selectivity was evaluated. Diphenylmethane was converted with 94% conversion and 100% selectivity to benzophenone under the optimized reaction conditions, in which the turnover number (TON) of catalyst reached 94,000. Moreover, a plausible reaction mechanism through redox ruthenium species was proposed.     

Synthesis and investigation of monomodal hydroxy-functionalized PEG methacrylate based copolymers with high polymerization degrees. Modification by “grafting from”

The synthesis of monomodal copolymers with poly(ethylene glycol) (PEG) side chains from commercial poly(ethylene glycol) methacrylates (PEGMA) by atom transfer radical polymerization (ATRP) is verified. Two hydroxy-functionalized PEGMA macromonomers (520 g/mol and 360 g/mol) were copolymerized with methyl methacrylate (MMA) using various initial feed (1.5/98.5–50/50 mol.%). The copolymers P(MMA-co-PEGMA) with high degree of polymerization, e.g. 100–275 of repeating units in the backbone including 7–56 PEG side chains, were obtained. The relative reactivity ratios of PEGMA and MMA determined by the Jaacks method indicated slightly faster incorporation of macromonomer into polymeric chain than MMA (r_MMA = 0.79; r_PEGMA = 1.27). The polymers containing at least 17 mol.% of PEGMA units were water-soluble and exhibited clouding point at temperature in a broad range of 39–70 °C. The temperature-sensitive effect makes these polymers as a potential carriers in drug delivery systems. In the case of copolymers insoluble in water, a three-step procedure, including esterification to ATRP multifunctional macroinitiators, ATRP of tert-butyl methacrylate (tBMA) by grafting from, deprotection of carboxylic groups by removing tert-butyl groups, was applied to extend PEG grafts and expand the content of hydrophilic fraction (32–94 mol.%), what efficiently developed polymer solubility in polar solvents giving possibility for the future biomedical applications.     

Synthesis of amphiphilic copolymers by ATRP initiated with a bifunctional initiator containing trichloromethyl groups

Bifunctional polystyrene macroinitiators, having various molecular weights, were prepared by atom transfer radical polymerization (ATRP), initiated with bifunctional initiator 1,3-bis{1-methyl-1[(2,2,2-trichloroethoxy) carbonylamino]ethyl}benzene in conjunction with CuCl catalyst and polyamine ligands. These macroinitiators were subsequently used for ATRP of tert-butyl acrylate (t-BuA), giving BAB triblocks poly[(t-BuA)-b-(Sty)-b-(t-BuA)] as precursors of amphiphilic copolymers. Both the polymerization steps proceeded as controlled processes with linear semi-logarithmic conversion plots and lengths of the blocks following theoretical predictions. Hydrolysis of outer poly(t-BuA) blocks led to triblock copolymers with the central polystyrene block and outer blocks of poly(acrylic acid), the molecular weights of which ranged from ca. 5 × 10³ to almost 1 × 10⁵ Da.     

Liquid–liquid equilibria for ternary mixtures of methyl tert-butyl ether,ethyl tert-butyl ether,water and imidazolium-based ionic liquids at 298.15 K

The ternary liquid–liquid equilibria (LLE) were analytically determined at 298.15 K for the following systems: {methyl tert-butyl ether (MTBE) + water + 1-ethyl-3-methylimidazolium-ethylsulfate (EMISE)}, {MTBE + water + 1-butyl-3-methylimidazolium-tetrafluoroborate ([Bmim][BF₄])}, {ethyl tert-butyl ether (ETBE) + water + EMISE}and {ETBE + water + [Bmim][BF₄]}.All the determination were carried out at atmospheric pressure using stirred and thermo-regulated cells. The experimental data were correlated with the well-known NRTL and UNIQUAC activity coefficient models. In addition, distribution coefficients with selectivity of the ionic liquids EMISE and [Bmim][BF₄] for water in the MTBE or ETBE phase were determined.     

Catalytic oxidation of isophorone to ketoisophorone over ruthenium supported MgAl-hydrotalcite

Selective oxidation of α-isophorone to ketoisophorone was carried out over Ruthenium supported MgAl-hydrotalcite in the temperature range 40–100 °C using acetonitrile as a solvent and tert-butyl hydroperoxide as an oxidant. The influence of various reaction parameters, such as reaction temperature, reaction time, substrate: catalyst mass ratio, substrate:oxidant mole ratio, and nature of solvent was studied. A maximum conversion of 60% KIP with 100% selectivity in 48 h was observed with a substrate: catalyst mass ratio of 10:1 at 60 °C.     

Polymeric structures of a pair of linear,dicarboxylate (tpy)2Ru2+ analogues

The preparation and solid-state structures of homoleptic Ru(II) complexes based on the ligands 4′-(4-carboxyphenyl)tpy (L₁) (where tpy = 2,2′:6′,2″-terpyridine) and 4′-(4-carboxyphenyl)-4,4″-di-(tert-butyl)tpy (L₂) are described. Both complexes are found to possess polymeric solid-state structures due to hydrogen-bonding interactions. The first complex, [Ru(L₁)₂]²⁺, exhibits a more closely-packed structure relative to that of [Ru(L₂)₂]²⁺, which was found to have a porous solid-state structure due to the steric bulk of the tert-butyl groups.     

Optimization,synthesis and characterization of vanadium-substituted thick-walled three-dimensional SBA-16

A systematic study was carried out to examine the viable synthesis condition at high acidic condition for the direct incorporation of a high level of vanadium into the 3D cubic arrangement of SBA-16 molecular sieves. The extent of mesopore structural ordering was determined by X-ray diffraction, N₂ physisorption, SEM and TEM analysis. The coordination and nature of the V sites were characterized by FT-Raman, electron spin resonance, ²⁹Si nuclear magnetic resonance spectroscopy, UV–visible diffuse reflectance spectroscopy and NH₃–TPD analysis. The surface area of calcined V-SBA-16 was ～1000 m²/g, while the mesopore volume of the SBA-16 cage ranged from 0.3 to 0.6 cm³g^?1. The pore size distribution was ～3.0 nm with a wall thickness of ～9.7 nm at the maximum. The Si/V ratios as determined by ICP-OES technique was varied from 438 to 8, respectively. The calcined samples exhibited promising catalytic activity in the oxidation of styrene with tert-butyl hydroperoxide as an oxidant.     

Synthesis of disubstituted amine-functionalized diene-based polymers

Diene-based polymers with two amine groups within each repeat unit were successfully synthesized by bulk and solution free radical polymerization techniques. All polymers have exclusive 1,4-microstructure. The number average molecular weights of the materials obtained were in the range of 30–52 × 10³ g/mol using 2,2′-azobisisobutyronitrile (AIBN), t-butyl peracetate (t-BPA), or t-butyl hydroperoxide (t-BHP) as the initiators. The highest molecular weight achieved was 72 × 10³ g/mol when t-butyl peroxide (t-BPO) was used as the initiator. Quantitative quaternization was achieved yielding hydrophilic water soluble polymers. Prior to quaternization, the polymers are hydrophobic and dissolve in most organic solvents.     

Two new 3-D coordination polymers with 5-tert-butyl isophthalic acid and flexible N-donor co-ligands bearing linear trinuclear secondary building blocks

Two new 3-D coordination polymers bearing linear trinuclear secondary building blocks with mixed bridging ligands, {[Ni₃(tbip)₂(Htbip)₂(bib)₂]·4H₂O}_n (1) and {[Co₃(tbip)₂(Htbip)₂(btb)₂]·4H₂O}_n (2) (H₂tbip = 5-tert-butyl isophthalic acid, bib = 1,4-bis(imidazol-1-yl)butane, btb = 1,4-bis(1,2,4-triazol-1-yl)butane), were obtained and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single-crystal X-ray crystallography and powder X-ray diffraction. Both complexes 1 and 2 display similar 3D 6-connected pcu networks containing the linear trinuclear [M₃(COO)₆] (M = Ni and Co) clusters as nodes.     

Catalytic olefin epoxidation with cationic molybdenum(VI) cis-dioxo complexes and ionic liquids

The complexes [MoO₂Cl(HC(bim)₃)]Y (Y = Cl (1), BF₄ (2) and PF₆ (3)) have been prepared by reaction of MoO₂Cl₂(THF)₂ (for 1) or [MoO₂Cl(THF)₃]Y (for 2 and 3) with the tridentate ligand HC(bim)₃ = tris(benzimidazolyl)methane, and characterized by IR and Raman spectroscopy, and ¹H NMR. The turnover frequencies for the epoxidation of cis-cyclooctene at 55 °C with tert-butyl hydroperoxide (TBHP, in decane) as the oxidant and complexes 1–3 as catalysts are in the range of 70–200 mol mol_Mo^?1 h^?1. 1,2-Epoxycyclooctane is always the only reaction product for reaction times up to 24 h. With the aim of facilitating the recyclability of the complexes, the ionic liquids (ILs) [BMIM]Y and [BMPy]Y (BMIM = 1-n-butyl-3-methylimidazolium, BMPy = 1-n-butyl-3-methylpyridinium; Y = BF₄ or PF₆) were applied as ionic solvents. The catalytic performance for cyclooctene epoxidation depends strongly on the catalyst solubility in the IL. Of the 12 catalyst/IL mixtures examined, the systems 1/[BMIM]PF₆ and 1/[BMPy]PF₆ exhibit the most favorable reaction rates allied with good recyclability. The 1/[BMIM]PF₆ system was further applied using different oxidants (aqueous TBHP, aqueous H₂O₂ and urea–hydrogen peroxide adduct) and olefins (norbornene, cyclohexene, styrene, α-pinene).     

Synthesis and photopolymerization of novel,highly reactive phosphonated-urea-methacrylates for dental materials

An urea methacrylate (1) and two phosphonated methacrylates (2–3) were synthesized from 2-isocyanatoethyl methacrylate (IEM) and benzyl amine (1), diethyl aminomethylphosphonate (2) and diethyl amino(phenyl)methylphosphonate (3). Their photopolymerization rates are notably higher than commercial monomers, despite the presence of only one double bond. Their polymerization rates follow the order 1 ～ 2 > 3 ～ triethylene glycol dimethacrylate (TEGDMA) > 2-hydroxyethyl methacrylate (HEMA). A tendency toward high crosslinking density during thermal bulk polymerizations, low oxygen sensitivity and high conversions with benzophenone during photopolymerization indicated the importance of hydrogen abstraction/chain transfer reactions. It was found that the addition of the monomers to HEMA significantly increased its polymerization rate, proving their utility as replacements for TEGDMA as reactive diluents for 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propyloxy) phenyl] propane (Bis-GMA). Copolymer systems containing 2 and 3 showed improved T_g values compared to Bis-GMA/TEGDMA systems.     

Palladium-catalyzed Mizoroki–Heck coupling reactions using sterically bulky phosphite ligand

A new catalytic system based on palladium-phosphite for Mizoroki–Heck coupling reactions of aryl iodide and bromide is described. An air-stable phosphite ligand afforded the desired products with high yields in the palladium-catalyzed Mizoroki–Heck reactions. The coupling of aryl iodides was optimized with 0.5 mol% Pd(OAc)₂, 1 mol% phosphite 2, and K₂CO₃ in DMF solvent. For the coupling of aryl bromides, 1 mol% Pd(OAc)₂ and 5 mol% phosphite 2 were required with Na₂CO₃ as base. As a coupling partner alkene, n-butyl acrylate, t-butyl acrylate, styrene and N-t-butyl acrylamide all showed good yields.     

Synthesis,reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpPOEtCo)VCl2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP^OEtCo)VCl₂(DMF) (1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP^OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C₂₀H₄₂Cl₂CoNO₁₀P₃V, crystallizes in the monoclinic space group P2₁/c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP^OEtCo)VCl₂(DMF) will be discussed. ((CpP^OEtCo) = [η⁵-cyclopentadienyltris(diethylphosphito-κ¹P) cobaltate(III)⁻; DMF = N,N-dimethylformamide).     

Design,synthesis, structure and magnetic behavior of a high spin binuclear Fe(III) complex of N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl) amine

The Mannich reaction of 2-aminoethanol, 2-tert-butyl-4-methylphenol, and formaldehyde at the ratio sets of 1:2:2 provided a new ligand, N-(1-ethanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L). In the presence of base, H₃L reacted with FeCl₃·6H₂O to form a dinuclear Fe(III) complex [Fe₂L₂] 1. The value of μ_eff at room temperature (5.95 μ_B), is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ ZS(S + 1)]^1/2], indicating there were strong interactions between Fe³⁺ ions. The effective magnetic moment (μ_eff) decreased abruptly with cooling to a minimum value of 0.1 μ_B at 2 K. It was worth noting that Fe³⁺ ions of 1 exhibited thermally induced quartet ? doublet spin transitions, and these transitions were abrupt. The magnetic behaviors of 1 denoted the occurrence of intramolecular anti-ferromagnetic interactions. J (? 13.58 cm^? 1) agrees with the result from Gorun–Lippard equation, ? J (cm^? 1) = Aexp(BP(Å) = 12.9).     

Synthesis and characterization of Ba1−xSrxTiO3 nanopowders by citric acid gel method

Stoichiometric and monophasic Ba_1−xSr_xTiO₃ (x = 0.3) nanopowders were successfully prepared by the citric acid gel method using barium nitrate, strontium nitrate and tetra-n-butyl titanate as Ba, Sr, Ti sources and citric acid as complexing reagent. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), infrared (IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the thermal decomposition behavior, the crystallization process and the particle size and morphology of the calcined powders. The results indicated that single-phase and well-crystallized Ba_1−xSr_xTiO₃ (x = 0.3) nanopowders with particle size around 80 nm could be obtained after calcining the dried gel at 950 °C for 2 h.     

Molecular markers of adhesion,maturation and immune activation of human osteoblast-like MG 63 cells on nanocrystalline diamond films

A semi-quantitative evaluation was made of the concentration of α_v- and β₁-integrins, integrin-associated proteins talin and vinculin, cytoskeletal protein β-actin, differentiation markers osteocalcin and osteopontin, and immunoglobulin adhesion molecule ICAM-1 (CD 54), using an enzyme-linked immunosorbent assay (ELISA), in human osteoblast-like MG 63 cells in 5-day-old cultures on hydrophilic oxygen-terminated nanocrystalline diamond (NCD) films with either nanoscale surface roughness (nano-NCD, RMS of 8.2 nm) or hierarchically organized submicron- and nanoscale roughness (RMS of 301.0 nm and 7.6 nm, respectively). The concentration of talin was significantly higher in cells on submicron-nano-NCD (by 36.0 ± 6.2% compared to the value on the polystyrene dishes). In addition, the concentration of vinculin increased on both nano-NCD and submicron-nano-NCD (by 19.8 ± 3.4% and 26.0 ± 6.1%, respectively). The concentration of integrins α_v and β₁, β-actin, osteocalcin, osteopontin and ICAM-1 were similar in the cells on both the NCD films and the control polystyrene surfaces. These results suggest that nanocrystalline diamond films give good support for colonization with osteogenic cells and could be used for surface modification of bone implants in order to improve their integration with the surrounding bone tissue, or for biosensor technology, where firm cell–substrate adhesion is also required.     

Electro-optical and electrochemical properties of an ionic polyacetylene derivative with azobenzene anisole moieties

An ionic polyacetylene derivative with azoanisole moieties was prepared by the activated polymerization of 2-ethynylpyridine by using 4-[4-(9-bromononyloxy)phenylazo]anisole without any additional initiator or catalyst in high yield. The chemical structure of poly[2-ethynyl-N-(p-methoxyphenylazophenyl)oxynonylpyridinium bromide] (PEMPB) was characterized by instrumental methods such as NMR (¹H and ¹³C), IR, UV–vis spectroscopies to have a conjugated polymer backbone system with the designed azobenzene moieties as substituents. This polymer was completely soluble in organic solvents and well processible. The electrochemical and electro-optical properties of PEMPB were studied. The cyclovoltammograms of this polymer exhibited the irreversible electrochemical behaviors between the oxidation and reduction peaks. The oxidation current density of PEMPB versus the scan rate is approximately linear relationship in the range of 30 mV/s–120 mV/s. The exponent of scan rate, x value of PEMPB, is found to be 0.6. The absorption spectrum starts around 700 nm and shows a characteristic absorption band at visible region of 464 nm due to the π → π* interband transition of the polymer backbone, which is a peak of the conjugated polyene backbone. The photoluminescence spectrum showed that the PL peak is located at 539 nm corresponding to the photon energy of 2.30 eV.     

Using modified Pechini method to synthesize α-Al2O3 nanoparticles of high surface area

A modified Pechini method for the preparation of a high surface area α-alumina is proposed. The synthesis of these nanoparticles was carried out using a polymer as a chelating agent. The polymer was prepared from citric acid and acrylic acid by the melt blending method. The resulting α-alumina (98.16%) after calcination at 900 °C consisted of cylindrical nanoparticles of 100–200 nm in length and <25 nm in diameter with a relatively high surface area (18 m² g^?1).