OCH CH Research Articles

Synthesis of onion-like mesoporous silica from sodium silicate in the presence of α,ω-diamine surfactant

Mesoporous silicas with vesicular and onion-like morphologies were assembled through hydrogen-bonding pathway from sodium silicate as silica source and electrically neutral α,ω-diamine, Jeffamine D2000 surfactant (H 2NCH(CH 3)CH 2[OCH 2CH(CH 3)] 33NH 2) as template in aqueous media at different synthesis temperatures (25, 60 and 100 °C). Assembling the material at 100 °C afforded onion-like core shell mesoporous silica, while at relatively lower temperature, e.g. 25 and 60 °C, multilamellar vesicles were obtained. Mesoporous silica with onion-like morphology was also obtained by a two-step synthesis involving an aging period of 20 h at room temperature followed by a hydrothermal stage (1–12 h) at 100 °C. The heavily cross-linked ( Q 4/ Q 3 ratio of 4.43) onion-like mesophase silica exhibited high hydrothermal stability. The BET surface area, pore volume and KJS (Kruk-Jaroniec-Sayari) pore diameter of the onion-like mesoporous silica were found to be 464 m 2 g −1, 1.16 m 3 g −1 and 7.2 nm, respectively.

Cationic and anionic environments in LiTFSI-doped di-ureasils with application in solid-state electrochromic devices

Fourier Transform mid-infrared and Raman spectroscopies were used to investigate the cation/polymer, cation/urea bridge, cation/anion and hydrogen bonding interactions in poly(oxyethylene) (POE)/siloxane di-ureasil networks prepared by the sol–gel route and doped with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Materials with compositions 200 ⩾ n ⩾ 5 (where n expresses the molar ratio OCH 2CH 2/Li +) were studied. The Li + ions coordinate to the urea carbonyl oxygen atoms over the whole range of salt concentration considered. Bonding to the ether oxygen atoms of the POE chains occurs at n ⩽ 40, although a significant fraction of the POE chains remain non-coordinated. In these high salt content samples, the cations interact with the anions forming contact ion pairs. “Free” ions are probably the main charge carriers at the room temperature conductivity maximum of these ormolytes.

Thermochemical behaviour of straight-chain ethers CH 3O(CH 2CH 2O) nCH 3 ( n = 1–4) in aqueous and tetrachlormethane solutions

The enthalpies of solution Δ sol H m of straight-chain polyethers CH 3O(CH 2CH 2O) n CH 3 ( n = 1–4) have been measured in water and tetrachlormethane as inert reference solvent at temperature of 298.15 K. The enthalpic coefficients of pairwise interaction and enthalpies of solvation were determined. The interaction between ether molecules in inert solvent are dominated by electrostatic forces resulting in the negative coefficients of interaction. In water the coefficients of interaction are positive. This is because the partial destruction of hydrophobic and hydrophilic shells becomes the predominant contribution to the coefficient. The enthalpy of solvation of one ethane oxide group in water is more negative than in tetrachlormethane by −7.4 kJ mol −1 that was related to the prevailing contribution of hydrogen bonding between ether and water molecules. The comparison of enthalpic characteristics was performed for the open-chain and cyclic ethers. The more exothermic effect of hydration of CH 2CH 2O group is observed for cyclic ethers. The distinction is connected with strengthening of hydrogen-bond bridges between adjacent ether oxygen atoms in cyclic molecule.

Kinetics of the reactions of chlorine atoms with selected fluoroacetates at atmospheric pressure and 298 K

The kinetics of the reactions of chlorine atoms with four fluoroacetates (FACETs) have been studied by the relative kinetic method at 298 ± 2 K and atmospheric pressure (760 ± 10 Torr) in a 1080 l quartz-glass photoreactor using in situ FT-IR spectroscopy for the detection of the organics. The following rate constants (in units of cm 3 molecule −1 s −1) were derived: k(Cl + CF 3C(O)OCH 3) = (0.90 ± 0.30) × 10 −13, k(Cl + CF 3C(O)OCH 2CH 3) = (1.78 ± 0.57) × 10 −12, k(Cl + CF 2HC(O)OCH 3) = (2.03 ± 0.65) × 10 −13 and k(Cl + CF 3C(O)OCH 2CF 3) = (1.18 ± 0.43) × 10 −15. The errors quoted are a combination of the 2 σ statistical errors and a 20% error in the reference reactions. Reactivity trends with respect to the degree and position of halogen substitution in the acetate are discussed together with possible atmospheric implications of the reactions.

Synthesis and characterization of crystalline CuS nanorods prepared via a room temperature one-step, solid-state route

We described a novel and simple one-step, solid-state route for the synthesis of crystalline CuS nanorods using surfactant, C 18H 37(CH 2CH 2O) 10H, as shape controller. The diameters of the as-prepared CuS nanorods are in the range of 10–60 nm and lengths are up to 5 μm. The crystallinity, purity, morphology, structural features and UV–vis optical absorption spectra of the as-prepared nanorods were characterized by X-ray diffraction, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, optical absorption spectra and X-ray photoelectron spectra. The role of surfactant, C 18H 37(CH 2CH 2O) 10H, in the formation of CuS nanorods has been discussed. The result indicated that the surfactant played a key role for the formation of CuS nanorods.

Synthesis, characterization and catalytic activity of highly ordered hexagonal and cubic composite monoliths

Design of nanocatalysts for efficient heterogeneous catalytic systems is needed to high ingredients for environmental cleanup of organic pollutant species. Here, well-defined order NiO–silica monolithic catalysts with hexagonal P6mm and cubic Pm3n mesostructures were successfully fabricated by using an instant direct-templating method of lyotropic and microemulsion phases of Brij 76 (C 18H 37(OCH 2CH 2) 10OH, C 18EO 10). Ordered hexagonal P6mm NiO/HOM-2 monoliths could be fabricated in lyotropic system of Brij 76 at phase composition domains of TMOS/Brij 76 (50 wt%). However, periodically ordered cubic Pm3n NiO-supported monoliths were synthesized in microemulsion system formed by addition of C 12-alkane to the hexagonal phase domains. This synthetic strategy also revealed that the NiO particles were well-dispersed into the silicate pore surface matrices of mesostructures. Monolithic NiO–silica composites with 2D hexagonal and 3D cubic geometries and with large particle morphologies show promise to act as catalysts. The current study revealed evidence of the advantages of nanoscale pore geometry and shape, and particle morphology of the supported silica monoliths in the design of nanocatalysts that can efficiently enhance the catalytic functionality in terms of stability, reversibility and reactivity. Furthermore, a key finding in our study was that 2D hexagonal and 3D cubic mesostructured NiO–silica catalysts retained the specific activity towards the oxidation reaction even after several regeneration/reuse cycles. Significant study of the mechanistic cyclization of the organic reactant using the density functional (DFT) calculations provided evidence of the key components of conformations of the functional model during the formation of the oxidation product.

Practical synthesis of 1,4-dioxane derivative of the closo-dodecaborate anion and its ring opening with acetylenic alkoxides

Practical method of synthesis of the 1,4-dioxane derivative of the closo-dodecaborate anion was developed. The cleavage of the dioxonium ring in [B 12H 11O(CH 2CH 2) 2O] − with acetylenic alcohols gave rise to the preparation of closo-dodecaborate derivatives with terminal acetylene group. These compounds can be introduced into click reactions with phenylazide leading to the corresponding triazoles. The structures of (Bu 4N)[B 12H 11O(CH 2CH 2) 2O] and (Bu 4N) 2[B 12H 11(OCH 2CH 2) 2OCH 2C CH] · 0.5HOCH 2C CH were determined by single-crystal X-ray diffraction.

Direct synthesis and characterization of highly ordered functional mesoporous silica thin films with high amino-groups content

A series of continuous, crack-free, highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of cationic CH 3(CH 2) 15N +(CH 3) 3Br − (CTAB), nonionic C 16H 33(OCH 2CH 2) 10OH (Brij-56) or triblock copolymer H(OCH 2CH 2) 20(OCH(CH 3)CH 2) 70(OCH 2CH 2) 20)OH (P123) surfactant species under acidic conditions by sol–gel dip-coating. The molar ration of APTES/(TEOS + APTES) in the starting sol attains a value of 0.4. The effect of the sol aging on the mesostructure of thin films is systematically studied, and the optimal sol aging time is obtained for different surfactant systems. The amino-functionalized mesoporous silica thin films exhibit long-range ordering of 2D hexagonal ( p6 mm) and 3D cubic ( Fm3 m) pore arrays of size range from 2.2 to 8.3 nm following surfactants extraction as demonstrated by XRD, TEM and physical adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for thin films prepared using different surfactants is calculated to be 3.2 and above amino-groups per nm 2, which is very useful and promising for incorporating inorganic ions and biomolecules into these mesoporous silica materials.

Chemistry of cyclodicarbaphosphatriazene: Synthesis and structural studies of pentaerythritoxy-bridged and lariat ether type spirocyclic derivatives

Reactions of dilithiated diols [HO(CH 2CH 2O) n+1 H, n = 1, 2 and 3] with 3,5-bis( N, N-dimethylamino)-1,1-dichlorodicarbaphosphazene ( 1) in THF have been carried out to afford the first examples of lariat ether type cyclocarbaphosphazene derivatives (C 4H 8O 3PN)(Me 2NCN) 2 ( 2), (C 6H 12O 4PN)(Me 2NCN) 2 ( 3) and (C 8H 16O 5PN)(Me 2NCN) 2 ( 4). Reaction of the tetrasodium salt of pentaerythritol with 1 and bis(morpholino)dichlorodicarbaphosphazene ( 1a) yielded the first examples of pentaerythritoxy-bridged cyclodicarbaphosphatriazenes [(Me 2NCN) 2PN(OCH 2) 2] 2C ( 5) and [(OC 4H 8NCN) 2PN(OCH 2) 2] 2C ( 6). The spectral and structural properties of these compounds are determined and compared with spirocyclic 1,3-propanedioxy derivative of 1 ( 7) and analogous compounds of cyclophosphazenes. The crystal structures of the compounds 4, 5 and 7 are reported. In addition, complexation studies of compounds 3 and 4 with Na I, K I, Ag I and Cu II ions were carried out by conductance measurements. The studies indicate mostly 1:1 complex formation between the metal ions and lariat ether type cyclocarbaphosphazene derivatives.

One-step synthesis of pentavalent triphenylantimony derivatives Ph 3Sb(OSiR 3) 2, Ph 3Sb(OCH 2CH 2) 2NH and Ph 3Sb(OCH 2CH 2NMe 2) 2: X-ray molecular structure of Ph 3Sb(OSiMe 3) 2

Pentavalent bis(triorganosiloxy)triphenylantimony derivatives, Ph 3Sb(OSiR 3) 2 (R = Me, Ph), were synthesized by reaction of triphenylantimony with trimethyl- or triphenylsilanol in the presence of tert-butylhydroperoxide by the mild reaction conditions (0–5 °C, 2 h). The reaction of triphenylantimony with diethanolamine in the presence of tert-butylhydroperoxide gave the cyclic compound Ph 3Sb(OCH 2CH 2) 2NH. The mixture of Ph 3SbO and Ph 3Sb(OCH 2CH 2NMe 2) 2 was obtained by the reaction of triphenylantimony with 2-( N, N-dimethylamino)ethanol in the presence of tert-butylhydroperoxide.

Matrix isolation study of ethyl chloroformate, ClC(O)OCH 2CH 3

The FTIR spectra of the syn-anti and syn-gauche forms of ethyl chloroformate, ClC(O)OCH 2CH 3, isolated in solid argon or nitrogen, were presented and completely assigned. Photolysis of the matrixes with broad band UV–visible radiation results in a decrease of the intensities of the IR absorptions assigned to the most stable syn-anti conformer while the corresponding to the less stable syn-gauche form increase their intensities. Besides the randomisation process, no changes were observed in the matrix spectra upon irradiation. The IR spectra of the two conformers were simulated using DFT methods (B3LYP/6–311++G**), and the predicted conformational ratio was 62% of the syn-anti form and 38% of syn-gauche conformer.

Covalent binding of a Fischer-type metal carbene in ordered mesoporous MCM-41-functionalized silica

The synthesis of ordered mesoporous silicas has received extensive attention due to their ordered arrangement, large surface area, and chemical stability. The pore size and pore volume of these materials make them suitable potential matrices for hosting. Here, we show that the covalent grafting of the Fischer carbene complex of tungsten [(CO) 5W C(ph)OCH 2CH 3] onto the silanol groups in inner walls of ordered mesoporous MCM-41 silica has been successfully accomplished. The introduction of the carbene complex is made by following two distinct anchoring procedures. The first one goes through the reaction of a mesoporous silica functionalized with 3-aminopropyltriethoxy silane (APTES) and a tungsten carbene, while in the second approach a precursor previously synthesized by reacting APTES with the tungsten carbene is then anchored via a direct bond with the silanol groups of the interior mesoporous pore channels of silica. XRD, N 2 adsorption/desorption, and TEM analysis provide strong evidence that the mesoporous support structure retains its long range ordering after the grafting process, despite a significant reduction of its specific surface area, pore volume and pore size. The chemical bonding of the tungsten carbene complex on the pore channels is also clearly confirmed by means of FTIR and solid-state NMR spectroscopy.

Molecular precursors of mesostructured silica materials in the atrane route: A DFT/GIAO/NBO theoretical study

Quantum chemical calculations using density functional theory have been carried out to investigate two assumed molecular precursors and identified as silatranes (N[OCH 2CH 2] 3Si–OCH 2CH 2N–(CH 2CH 2OH) 2 and N[OCH 2CH 2] 3Si–OCH 2CH 2N–(CH 2CH 2OH) 2Na +) which are present in the synthesis of mesoporous silica based material namely “the atrane route”. One of the ways in this synthesis leads to the well-known MCM-41. Additionally, in this work has been also investigated two others molecules such as triethanolamine (TEAH3) and sodatrane which are present in the medium. Gas phase and solution equilibrium geometries of the previous molecules were fully optimized at B3LYP level, modeling solvent effects using a self-consistent reaction field (SCRF) Onsager model, a discrete electrostatic representation of triethanolamine molecules in the first solvation shell. Calculations of the 1H and 13C NMR chemical shifts at GIAO/B3LYP/6–31G(d,p) levels of theory are also presented. The importance of basis set is previously discussed in the GIAO calculations. Finally, a natural bond orbital (NBO) analysis has been performed to provide insight into the role of electronic delocalization in the chemical shielding. This work has shown that the assumed geometries of the molecular precursors that have been deduced from a previous work on a FAB-MASS analysis (Fast Atomic Bombardment Mass Spectroscopy) are confirmed by DFT calculations. The theoretical study on the chemical shifts of nucleus as 13C and 1H from full geometry optimizations of the molecular precursors and sodatrane describes hydrogens bonded to each CH 2O and CH 2N groups as not equivalent; in the same way, it appears that some carbons are not magnetically equivalent. GIAO calculations from a full geometric optimization of TEAH3 overestimate the experimental chemical shifts; however, a threefold-symmetry (C3) of optimized geometry yields an improvement of the theoretical chemical shifts. The discrepancies in the GIAO calculations might be related to the hyperconjugative interactions such as LP O1 → σ*(C–X), LP O2 → σ*(C–X) and LP N → σ*(C–X) with X = C, H and also σ → σ*(C–X) with X = O; N, H. These interactions are characterized by delocalization energies which are generally important and peculiarly for LP → σ*(C–X). A reasonable level of agreement between GIAO calculations and experimental NMR studies is obtained which confirms the presence of the molecular precursors in the “atrane route” and taking into account the hyperconjugative interactions might explain some discrepancies in GIAO calculations.

Small-angle X-ray scattering (SAXS) study on nonionic fluorinated micelles in aqueous system

We have investigated the self-organization structures of perfluoroalkyl sulfonamide ethoxylate, C 8F 17SO 2N(C 3H 7)(CH 2CH 2O) 10H, a nonionic fluorinated surfactant in aqueous system by small-angle X-ray scattering (SAXS) technique. Structural modulation of the nonionic fluorinated micelle induced by temperature change, surfactant concentration, and the added fluorinated oils have been systematically studied. The SAXS data were analyzed by the indirect Fourier transformation (IFT), and the generalized indirect Fourier transformation (GIFT) depending on the volume fraction of the surfactant. Various plausible classical model calculations have been performed to confirm the consistency of the GIFT analysis of the SAXS data. Upon successive increase in temperature, the cylindrical micelles formed at lower temperatures undergo a continuous one-dimensional growth and ultimately near the cloud point an indication of flat planar like structural pattern is observed. The evolution in structure of particle near the demixing temperature may be due to onset of attractive interactions. The shape and size of the micelle is apparently unaffected by changing the surfactant concentration from 1 to 5 wt% at 25 °C. Nevertheless, addition of small amount of perfluoropolyether (PFPE) oil, of structure F (CF 2CF 2CF 2O) n CF 2CF 2COOH ( n ∼ 21 ) modulate the micellar shape and size. Long cylindrical micelles eventually transform into globular like particles. The onset cylinder-to-sphere transition in the structure of micelles in the surfactant/water/oil system is probably due to amphiphilic nature of the oil, which tends to increase the spontaneous curvature. The lipophilic part of the oil tends to reside in the micellar core, whereas, the hydrophilic part goes close to the polar head group of the surfactant so that effective cross-sectional area per surfactant molecules increases and as a result spherical micelles tend to form. Perfluorodecalin (PFD) also decreases size of the micelles but its effect is poor compared to the PFPE oil.

8-Dioxane ferra(III) bis(dicarbollide): A paramagnetic functional molecule as versatile building block for introduction of a Fe(III) centre into organic molecules

The synthesis of a new, paramagnetic closo-[(8-(-CH 2CH 2O) 2-1,2-C 2B 9H 10)(1′,2′-C 2B 9H 11)-3,3′-Fe] 0 ( 3) is reported. This compound can serve as a versatile building block for construction of both anionic and zwitterionic derivatives, as exemplified by the synthesis of a series of compounds of general formula closo-[(8-X-(CH 2CH 2O) 2-1,2-C 2B 9H 10)(1′,2′-C 2B 9H 11)-3,3′-Fe], bearing organic end groups (X = NC 5H 5 ( 4), (C 6H 5) 3P ( 5), OH ( 6), and 2-O(1-CH 3O–C 6H 4) ( 7)) attached to the cluster by a diethyleneglycol spacer. Molecular structures of 3, 4, 5 and 7 were determined by single-crystal X-ray diffraction analysis and by the long-time neglected method of paramagnetic, high field NMR ( 1H, 13C and 11B) spectroscopy.

Effect of temperature on the rheology of wormlike micelles in a mixed surfactant system

The formation and rheological behavior of a viscoelastic wormlike micellar solution in an aqueous solution of a mixed surfactant system of alkyl ethoxylate sulfate (AES), C 12H 25(OCH 2CH 2) 3OSO − 3Na +, and polyoxyethylene dodecyl ether, C 12EO 3, and the unusual effect of temperature on the rheological behavior have been studied. Upon successive addition of C 12EO 3 to the dilute micellar solution of AES, viscosity increases swiftly and reaches its peak where a viscoelastic solution with nearly Maxwellian behavior is formed. With the further addition of C 12EO 3, viscosity decreases sharply, which is attributed to the formation of micellar joints. With increasing temperature, the extent of micellar growth increases and the viscosity maximum is achieved at a lower mixing fraction of C 12EO 3, but the maximum viscosity attained by the system decreases. The evolution of relaxation time and network density of the viscoelastic network also suggests that with increasing temperature, enhanced micellar growth takes place, but an additional, faster relaxation mechanism becomes increasingly favorable at high concentrations of C 12EO 3. These results can be explained in terms of the increase in free energy of hemispherical end-caps (end-cap energy) of the micelles with increasing temperature.

Incorporation of a tungsten Fischer-type metal carbene covalently bound to functionalized SBA-15

A metal Fischer carbene [(CO) 5W C(φ)OCH 2CH 3] was covalently linked for the first time to the silanol groups of the mesoporous channels of SBA15 by following two different synthetic anchoring routes. The first one goes through the reaction of the SBA15 mesoporous silica walls functionalized by aminopropyltriethoxysilane (APTES) with a tungsten carbene Wφ, while in the second approach a precursor synthesized by reacting APTES with the carbene Wφ is then anchored via a direct bond to the silanol groups in the interior pore channels of SBA-15. This tethering is helpful to prevent the decomposition of the metallic complex. XRD, N 2 adsorption–desorption, and TEM analysis provide strong evidence that the mesoporous support structure retains its long-range ordering after the grafting process, despite a significant reduction of its specific surface area, pore-volume and pore-size. The chemical bonding of the tungsten carbene to the silanol groups of SBA-15 materials was studied with solid-state NMR spectroscopy. Both 13C MAS NMR and 29Si CP MAS NMR spectra confirm the covalent linking of the carbene to the silica-pore system.

Formation of Pd nanoparticles in surfactant-mesoporous silica composites and surfactant solutions

Highly dispersed palladium nanoparticles containing mesoporous silicas MCM-41 and MCM-48 were prepared by one-pot synthesis. The method consists of the simultaneous formation of CTA + surfactant templating MCM-41 mesophase and CTA + micelle-capped PdO, which was reduced by hydrogen to Pd metal with particle size ≈ 2 nm and was observed to stay inside the mesochannels of MCM-41 (pore size ≈ 3.8 nm) by TEM, XAS, and PXRD. During hydrothermal synthesis of Pd/MCM-48, Pd nanoparticles of average size ≈ 6–7 nm were deposited on the MCM-48 of pore size = 4 nm. The deposition is probably derived from ethanol reduction of Pd(II) complex generated from PdCl 2 precursor by hydrolysis of TEOS and C 12H 25(OCH 2CH 2) 4OH surfactant. The formation of Pd(0) from Pd(II) species in solid mesoporous silicas by hydrogen reduction was monitored by in situ XAS, and compared with the formation of Pd(0) from [PdCl 4] 2−, [PdCl 3(H 2O)], and Pd(OH) 2 by sodium dodecyl sulfate surfactant and alcohol reduction in aqueous solutions.

Electronic structure and luminescence of [AuS 2PPh(OCH 2CH [dbnd]CH 2)] 2 complex

The complex [AuS 2PPh(OCH 2CH CH 2)] 2 ( 1) presents an Au(I)–Au(I) intramolecular and intermolecular bonding with luminescence properties. To understand the nature of these features, fully optimized geometries were obtained by three computational methods, DFT/B3LYP, MPW1B95 and MP2. An Au(I)–Au(I) intramolecular bond was found in the ground state, at the three levels of theory, exhibiting an aurophilic interaction between the two gold atoms. Two molecules of the complex were optimized using DFT/B3LYP, in order to analyze the intermolecular interaction between them. The resulting intermolecular bonding distance between the two adjacent gold atoms on each molecule is 3.16 Å, indicating a strong aurophilic attraction. Time dependent calculations indicate that the first excited state with nonzero oscillator strength is a singlet, with an excitation energy equal to 3.16 eV. This should correspond to the absorption band seen experimentally at 3.10 eV. The lowest energy emission of ( 1) was obtained at 2.73 eV, which corresponds to the emission peak resulting from phosphorescence and located at 2.53 eV. This transition comes from an excited electron on the p orbitals of the ligands that is transferred to the d orbitals of the gold atoms on the HOMO. This interaction may be attributed to Ligand to Ligand–Metal Charge Transfer (LL–MCT).

Surface activity and association behavior of nonaoxyethylene n-dodecylether in aquo amino acid medium: Tensiometry, small-angle neutron scattering, dynamic light scattering and viscosity studies

Solubility, tensiometric, small-angle neutron scattering (SANS), dynamic light scattering (DLS) and viscometric measurements were carried out to elucidate the solution and morphological properties of nonaoxyethylene n-dodecyl ether [CH 3(CH 2) 11(OCH 2CH 2) 9OH], C 12E 9 over a limited range of temperature and surfactant concentration, both in the presence and in the absence of amino acids (AAs) The amino acids used were glycine, alanine and valine. Clouding temperatures of C 12E 9 under various conditions were determined. Surface tension was used to determine the critical micelle concentrations (CMC) of surfactant–amino acid mixtures. It seems that the structure breaking ability of AAs and their possible interaction with surfactant affect the micellization process. Viscosity, SANS, and DLS measurements of the surfactant solutions were done and the aggregation number and hydrodynamic radii were computed at three different temperatures of 30, 45 and 60 °C. Among the AAs investigated, the effect of alanine was found to be different from the other amino acids.