Formation of self-assembled monolayers of π-conjugated molecules on TiO2 surfaces by thermal grafting of aryl and benzyl halides

We demonstrate the formation of molecular monolayers of π-conjugated organic molecules on nanocrystalline TiO(2) surfaces through the thermal grafting of benzyl and aryl halides. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were used to characterize the reactivity of aryl and benzyl chlorides, bromides, and iodides with TiO(2) surfaces, along with controls consisting of nonhalogenated compounds. Our results show that benzyl and aryl halides follow a similar reactivity trend (I > Br > Cl > H). While the ability to graft benzyl halides is consistent with the well-known Williamson ether synthesis, the grafting of aryl halides has no similar precedent. The unique reactivity of the TiO(2) surface is demonstrated using nuclear magnetic resonance spectroscopy to compare the surface reactions with the liquid-phase interactions of benzyl and aryl iodides with tert-butanol and -butoxide anion. While the aryl iodides show no detectable reactivity with a tert-butanol/tert-butoxide mixture, they react with TiO(2) within 2 h at 50 °C. Atomic force microscopy studies show that grafting of 4-iodo-1-(trifluoromethyl)benzene onto the rutile TiO(2)(110) surface leads to a very uniform, homogeneous molecular layer with a thickness of ～0.45 nm, demonstrating formation of a self-terminating molecular monolayer. Thermal grafting of aryl iodides provides a facile route to link π-conjugated molecules to TiO(2) surfaces with the shortest possible linkage between the conjugated electron system and the TiO(2).     

Synthesis,chemical properties,and CO2 electroreduction of π-conjugated polymers bearing imidazolium and imidazolinium rings in the polymer backbone

π-Conjugated polymers (CPs) bearing imidazolium and imidazolinium rings in the polymer backbone were prepared from a previously reported monomer, 1,3-bis(2,3-dimethyl-4-bromophenyl)imidazolium chloride, and a newly synthesized monomer, 1,3-bis(2,3-dimethyl-4-bromophenyl)imidazolinium chloride, via Sonogashira and Suzuki–Miyaura coupling reactions. The corresponding model compounds were also synthesized via the same reactions and monomers. The absorption maxima and onset position of the UV–vis spectra of the polymers were observed at longer wavelengths than those of the model compounds, thus revealing the presence of extended π-conjugation along the polymer backbone chain. Both polymers and model compounds were photoluminescent in solution and exhibited solvatochromism. The cast films of the polymers on the Pt and Ag electrodes were demonstrated to be effective catalysts for CO₂ electroreduction.     

Kinetics of CO2 absorption by aqueous mixtures of N,N′-diethylethanolamine and polyamines

Aqueous solutions of N,Nʹ-diethylethanolamine (DEEA) are prospective high-capacity CO₂-capturing solvents. Their reactivity can be enhanced by promotion with absorption activators. Two polyamines were chosen as activators in this work, viz. (methylamino)propylamine (MAPA) and diethylene triamine (DETA). In a stirred cell reactor, kinetics of CO₂ absorption into aqueous DEEA/MAPA and DEEA/DETA mixtures was studied at 303 K. The molarity of DEEA was varied in the 2–2.5 M range, whereas the polyamine concentration was changed between 0.1 and 0.5 M. Pseudo–first-order rate constants were reported. Second-order rate constants for the CO₂ reactions with MAPA and DETA were determined too. DETA reacts faster than MAPA.     

Catalytic Activity and Stability of Mo_2N in CO Oxidation

Inrecentyears,Mo2Nhasreceivedgreatattenti0ninheter0geneouscatalysisduetoitshighspecificsurfaceareal-4.IthasgoodcaIalyticactivityinawidevarietyofreactions,suchasthehydr0genati0nofCO,synthesis0fNH3,methanation,hydrodenitrogentionandhydrodesulfurization"'andInightbeaprondsingcatalyticmaterial.ThepreparationofMo2Nasacatalyticmaterialhasgainedgreatprogress.Theproduction0fMo2Nwithhighspecificsurfacearea(l7Om'g-')intemperatureprogranunedreactions(TPR)0fMoo3innowingN-H3wasreported'.InthisLab,…     

Novel thiophosphonodiamides as efficient hydrogen bond donor catalysts in tandem Michael addition–cyclization of malononitrile and 2-(E)-2-nitrovinylphenols

From l-amino acid, three chiral thiophosphonodiamides were prepared as new hydrogen bond donor organocatalysts. Under the mediation of the catalyst derived from l-valine, a tandem Michael addition/cyclization reaction between (E)-2-(2-nitrovinyl)phenols and malononitrile proceeds smoothly, giving pharmaceutically valuable 2-amino-4H-chromene-3-carbonitriles in high yields with 66–95% ee within 2 h.     

Chiral and extended π-conjugated bis(2-pyridyl)phospholes as assembling N,P,N pincers for coordination-driven synthesis of supramolecular [2,2]paracyclophane analogues

Chiral, π-conjugated 3,4-butano-1-phenyl-2,5-bis(2-pyridyl)phosphole derivatives 1a(2,2') and 1a(3) with chiral trans-1,2-diol moieties and fused pinene derivatives, respectively, were prepared from the corresponding chiral diynes by using the Fagan-Nugent method. Their UV/Vis absorption and chiroptical properties (optical rotation and circular dichroism) were studied. Their behavior as N,P,N chelates towards coordination of Cu(I) and formation of chiral supramolecular assemblies with π-conjugated ditopic dicyano ligands was investigated. Chiral C(2)-symmetric rectangles that are [2,2]paracyclophane analogues were obtained, as demonstrated by X-ray crystallography. During the course of this study, the first stable water-soluble phosphole derivative (1a(2)·2 HCl) was prepared. Furthermore, achiral 3,4-butano-1-phenyl-2,5-bis(aza[4]helicene)phosphole 1a(4) was synthesized and displays extended π conjugation. A supramolecular rectangle was obtained by coordination to Cu(I) and assembly with a dicyano stilbene. This coordination-driven supramolecular assembly contains a total of four aza[4]helicene moieties and displays two types of π-π stacking interactions in the solid state, that is, between two helicene moieties and between one helicene and a bridging dicyano ligand. All the supramolecular arrangements are discussed by comparing them with previous work on the parent 3,4-butano-1-phenyl-2,5-bis(2-pyridyl)phosphole.     

Combustion characteristics and kinetics of DPR Korea’s anthracite in O2/N2 and O2/CO2 atmosphere

Journal of Thermal Analysis and Calorimetry - In O2/N2 and O2/CO2 atmospheres with oxygen concentrations of 21%, 30%, and 50%, combustion characteristics index, apparent activation energy, and...     

Mechanisms of reactions between > Si=O groups and CO2, N2O, and HC≡CH molecules: An experimental and quantum chemical study

IR spectroscopy and quantum chemical calculations are used to study the directions and kinetics of reactions between silanone groups (≡Si-O)₂Si=O and CO₂, N₂O, and acetylene molecules. IR bands are assigned on the basis of the calculation of vibrational spectra of model low-molecular systems. Quantum chemical methods are used to obtain the data on the shapes of potential energy surfaces of these systems (intermolecular complexes and transition states). These data are used to interpret kinetic data. The silanone group is inclined to the formation of relatively stable (~10 kcal/mol) intramolecular complexes with CO₂, N₂O, and acetylene molecules. Their geometries and electronic structures are determined.     

Rare-earth metal amido complexes supported by bridged bis(β-diketiminato) ligand as efficient catalysts for hydrophosphonylation of aldehydes and ketones

A series of rare-earth metal amides supported by a cyclohexyl-linked bis(β-diketiminato) ligand were synthesized,and their catalytic activities for hydrophosphonylation of aldehydes and ketones were developed.Reaction of [(Me3Si)2N]3 RE(Cl)Li(THF)3 with the cyclohexyl-linked bis(-diketimine) H2L(1)(L=Cy[NC(Me)CHC(Me)NAr]2,Cy = cyclohexyl,Ar=2,6-i-Pr2C6H3) gave the rare-earth metal amides LREN(SiMe3)2(RE = Nd(2),Sm(3),Dy(4),Er(5),Y(6)).All complexes were fully characterized by elemental,spectroscopic and single-crystal X-ray analyses.Investigation of the catalytic properties of the complexes reveals that these complexes exhibited a high catalytic activity towards the hydrophosphonylation of aldehydes and ketones in the presence of a very low loading of rare-earth metal amides(0.1-1 mol%) at room temperature in a short time.     

Orientational order of guest molecules in aligned liquid crystal as measured by EPR and UV–vis techniques

Orientational order of guest molecules in aligned liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) is studied via optical dichroism and electron paramagnetic resonance (EPR) spectra measurements. The guest molecules used are bifunctional molecules bearing paramagnetic nitroxide group and photochromic azobenzene moiety. The bifunctional probe with rigidly bonded nitroxide and azobenzene moieties was found to align as a whole, while flexible long spacer between the moieties provides independent alignment for the nitroxide and azobenzene parts. Intermolecular interactions responsible for the alignment of azobenzene and nitroxide moieties of the probe molecules are discussed. The molecules with cis-configuration of azobenzene moiety are able to align in the liquid-crystalline medium, but to a lesser extent than the molecules with trans-configuration. Directions of orientational axes and characteristics of rotational mobility of spin probes are determined. Second, fourth and, in some cases, sixth rank order parameter values are found.     

Absolute radiolytic yields of N2(C3Πu) in N2/rare gas mixtures: Theoretical and experimental determinations

The absolute radiolytic luminescence yield for the emission from the C³Π_u state of N₂ has been determined for pulsed electron beam irradiation of He/N₂ and Ne/N₂ mixtures. The yields—corrected for all quenching processes—are compared to those calculated, by Monte-Carlo methods, from a model based on sub-excitation electron processes. The results confirm that this model and the Platzman initial sub-excitation electron distribution function are fully compatible with the observed results.The yields from experiment and theory are G(N₂, C³Π_u) = 0.079 ± 0.010 and 0.10 ± 0.01, respectively in He/N₂; 0.116 ± 0.037 and 0.094 ± 0.007 in Ne/N₂ mixtures.The G-values for absolute photon yields may be calculated from this data using appropriate kinetic quenching rate constants.     

Low-temperature CO oxidation over CuO-CeO2/SiO2 catalysts：Effect of CeO2 content and carrier porosity

The effects of CeO2 contents and silica carder porosity with their pore diameters ranging from 5.2 nm to 12.5 nm of CuO-CeO2/SiO2 catalysts in CO oxidation were investigated. The catalysts were characterized by N2 adsorption/desorption at low temperature, X-ray diffraction (XRD), temperature-programmed reduction by H2 (H2-TPR), oxygen temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS). The results suggested that, the ceria content and the porosity of SiO2 carder possessed great impacts on the structures and catalytic performances of CuO-CeO2/SiO2 catalysts. When appropriate content of CeO2(Ce content ≤8 wt%) was added, the catalytic activity was greatly enhanced. In the catalyst supported on silica carrier with larger pore diameter, higher dispersion of CuO was observed, better agglomeration-resistant capacity was displayed and more lattice oxygen could be found, thus the CuO-CeO2 supported on Si-1 showed higher catalytic activity for low-temperature CO oxidation.     

Dynamics of Gas Heating in the Afterglow of Pulsed CO2 and CO2–N2 Glow Discharges at Low Pressure

Plasma Chemistry and Plasma Processing - The time-dependent evolution of the energy transfer into gas heating in the afterglow of pulsed CO2 and CO2–N2 glow discharges produced in cylindrical...     

Heterogeneous bimetallic Au–Co nanoparticles as new efficient catalysts for the three-component coupling reactions of amines,alkynes and CH2Cl2

Research on Chemical Intermediates - Propargylamines are key intermediates for the synthesis of many biologically active molecules. A new synthesis of propargylamines via a three component-coupling...     

Assessment of the physical–chemical properties of residues and emissions generated by biomass combustion under N2/O2 and CO2/O2 atmospheres in a Drop Tube Furnace (DTF)

Journal of Thermal Analysis and Calorimetry - The present article investigates the effect of second-order slip, chemical reaction and Soret and Dufour effects on MHD convective flow of an Oldroyd-B...     

Infrared spectra of simple molecules in liquid-argon solution—II. NF3 and N2O

The i.r. spectrum of NF₃ has been measured in liquid-argon solution. Since the sample of NF₃ used for the experiments was contaminated with N₂O, it was also necessary to measure the spectrum of N₂O in liquid-argon solution so that the impurity bands could be identified unambiguously. In the observed spectrum of NF₃ it was possible to identify 29 overtone and combination bands in addition to the vibrational fundamentals. The measured wavenumbers of the NF₃ bands have been used to estimate the anharmonic coefficients x_ss′, which are compared with the corresponding quantities determined from the gas-phase spectrum.     

Adsorption of CO2 and N2 in Na–ZSM-5: effects of Na+ and Al content studied by Grand Canonical Monte Carlo simulations and experiments

Zeolite crystals with cations present, such as ZSM-5, are widely used for gas sequestration, separations, and catalysis. One possible application is as an adsorbent to separate CO₂ from N₂ in flue gas mixtures. Typically, the zeolite framework is of a SiO₂ composition, but tetravalent Si atoms can be replaced with trivalent Al atoms. This change in valence creates a charge deficit, requiring cations to maintain the charge balance. Experimental studies have demonstrated that cations enhance adsorption of polar molecules due to strong electrostatic interactions. While numerous adsorption studies have been performed for silicalite-1, the all-silica form of ZSM-5, fewer studies on ZSM-5 have been performed. Grand Canonical Monte Carlo simulations were used to study adsorption of CO₂ and N₂ in Na–ZSM-5 at T = 308 K, which is ZSM-5 with Na⁺ counter-ions present. The simulations suggest that a lower Si/Al ratio (or higher Na⁺ and Al content) substantially increases adsorption at low pressures. At high pressures, however, the effect of the Al substitutions is minor, because the Al^?/Na⁺ sites are saturated with guest molecules. Similarly, a lower Si/Al ratio also increases the isosteric heat of adsorption at low loading, but the isosteric heats approach the silicalite-1 reference values at higher loadings. Comparison of simulations and experimental measurements of the adsorption isotherms and isosteric heats points to the importance of carefully considering the role of charge on the Na⁺ cations, and suggest that the balancing cations in ZSM-5, here Na⁺, only have partial charges.     

Effect of cobalt precursors on the dispersion, reduction, and CO oxidation of CoO(x)/γ-Al2O3 catalysts calcined in N2

The present work tentatively investigated the effect of cobalt precursors (cobalt acetate and cobalt nitrate) on the physicochemical properties of CoO(x)/γ-Al(2)O(3) catalysts calcined in N(2). XRD, Raman, XPS, FTIR, and UV-vis DRS results suggested that CoO/γ-Al(2)O(3) was obtained from cobalt acetate precursors and CoO was dispersed on γ-Al(2)O(3) below its dispersion capacity of 1.50 mmol/(100 m(2) γ-Al(2)O(3)), whereas Co(3)O(4)/γ-Al(2)O(3) was obtained from cobalt nitrate precursors and Co(3)O(4) preferred to agglomerate above the dispersion capacity of 0.15 mmol/(100m(2) γ-Al(2)O(3)). Compared with Co(3)O(4)/γ-Al(2)O(3), CoO/γ-Al(2)O(3) catalysts were difficult to be reduced and easy to desorb oxygen species at low temperatures and presented high activities for CO oxidation as proved by H(2)-TPR, O(2)-TPD, and CO oxidation model reaction results. A surface incorporation model was proposed to explain the dispersion and reduction properties of CoO/γ-Al(2)O(3) catalysts.