Search

Metal-organic frameworks (MOFs) have received great attention due to their fascinating structures and intriguing potential applications in various fields. Herein, we report the first example of the utilization of MOFs for solid-phase microextraction (SPME). MOF-199 with unique pores and open metal sites (Lewis acid sites) was employed as the coating for SPME fiber to extract volatile and harmful benzene homologues. The SPME fiber was fabricated by in situ hydrothermal growth of thin MOF-199 films on etched stainless steel wire. The MOF- 199-coated fiber not only offered large enhancement factors from 19 613 (benzene) to 110 860 (p-xylene), but also exhibited wide linearity with 3 orders of magnitude for the tested benzene homologues. The limits of detection for the benzene homologues were 8.3-23.3 ng [L.sup.-1]. The relative standard deviation (RSD) for six replicate extractions using one SPME fiber ranged from 2.0% to 7.7%. The fiber-to-fiber reproducibility for three parallel prepared fibers was 3.5%-9.4% (RSD). Indoor air samples were analyzed for the benzene homologues using the SPME with the MOF- 199-coated fiber in combination with gas chromatography-flame ionization detection. The recoveries for the spiked benzene homologues in the collected indoor air samples were in the range of 87%-106%. The high affinity of the MOF-199-coated fiber to benzene homologues resulted from the combined effects of the large surface area and the unique porous structure of the MOF-199, the [pi]-[pi] interactions of the aromatic rings of the analytes with the framework 1,3,5-benzenetriearboxylic acid molecules, and the [pi]-complexation of the electron-rich analytes to the Lewis acid sites in the pores of MOF-199. 10.1021/ac901663x

The synthesis, isolation, and characterization of hexakis(4-(N-butylpyridylium))benzene as both a hexacation and neutral molecule are reported.

The systematic studies of pressure dependence of Raman spectra of benzene/C[O.sub.2] two-component system is carried out at different temperatures and compositions. The observation of the shift of the peak composition of the inhomogeneous bandwidth suggests that inter-molecular interaction between benzene and C[O.sub.2] molecules grow at low temperatures.

Using molecular dynamics (MD) simulations of a single solute in water the hydration structures of the hydrophobic solutes benzene and cyclohexane were investigated. Three-dimensional maps of the density of the water O and H atoms surrounding either benzene or cyclohexane were generated from the simulation data.

The effect of aromatic swelling agents on the pore geometry and pore size of mesoporous M41S materials is investigated, where benzene and 1,3,5-trisubstituted aromatic compounds are used as swelling agents. Benzene is incorporated and immobilized close to the surface of the micelle, whereas the more hydrophobic trisubstituted aromatic compounds are located in the hydrophobic core of the micelle, where they retain some mobility.

An ab initio calculations-backed model that allows the estimation of several ground-state charge separated systems is presented. It is observed that the charge separation is not associated with the aromatic nature of the precursor but with the ionization of the amino group and electron affinity of the dioxoallyl radical.

Optical and conductivity detection were used to study the reaction between deoxyribose radicals (dR) and benzotriazine compounds. The results give a mechanistic model showing the way tirapazamine interacts with the ribose component of DNA after the one-electron reductions.

The interaction energies of the alkaline-earth-metal dication/benzene complexes were calculated at the MP2 level using the 6-311G-basis set. The calculations of benzene under an electric field show that the electric field produced by the diction is a cause of the C-C bond elongation in the alkaline-earth-metal dication/benzene complexes.

The ultraviolet and infrared spectra of the C6H6-(C4H2)(sub n) complexes with n=1 and 2 were formed and studied in a supersonic expansion. A T-shaped structure is deduced for the complex, with the C4H2 centered, end on, over the benzene ring.

Study of the electrochemistry of a novel organic-inorganic material in which 4,4-bipyridinium units (BP) are covalently attached to the walls of a periodic mesoporous organisilica (PMO) of the MCM-41 type is reported. It was observed that the electrochemical response of regular mesoporous organosilica of the MCM-41 type containing bipyridinium units covalently attached vary significantly for as-synthesized material, BP@PMO.

Density-functional theory calculation, Monte Carlo simulations and thermodynamic perturbation theory calculations were carried out to analyze the differences between the solvation of phenol and phenoxy radical in benzene and acetonitrile. The theoretical calculations in this study indicated that the differences between the solvation which enthalpies of phenol (PhOH) and phenoxy radical (PhO(super .) in both benzene and acetonitrile are smaller.

Experimental evidence for a strong polar ordering induced by wire poling under high electric field conditions in the amorphous pDR1M azobenzene polymer is reported. A comparative study of the electronic spectra of a DR1 solution in chloroform and of an unpoled, a poled and a thermally depoled film is discussed.

The results of the research conducted on van der Waals complexes of aniline and 4-aminobenzonitrile with polar solvents formed in a supersonic jet is reported. It also reports the solvatochromism studies of all substituted benzenes and napthalenes.

The voltage sensitivity of hemicyanine dyes ANNINE-6 and ANNINE-5 with anellated benzene rings and without free CC single and double bonds is studied in Retzius neurons from Hirudo medicinalis. The Annine dyes are the most efficient fluorescent probes of neuronal activity on the basis of a well-defined physical mechanism.

Well-resolved spectra of styrene-methanol binary clusters SM(sub n), with n = 1-9, is obtained by the resonant two-photon ionization technique. It is proposed that the interaction of the methanol molecules with the olefin center of styrene promotes the proton transfer from the styrene dimmer to the hydrogen-bonded methanol cluster.

Density functional theory and ab initio calculations were used to investigate the structures of the chlorine atom-benzene complex and other halogen atom-benzene complexes. The n6 benzene-CI complex was found to have two degenerate imaginary vibrational frequencies and was estimated to have no strong absorptions above 300nm.

Hybrid density functional calculations are used to elucidate the mechanisms by which benzene is converted to phenol, benzene oxide, and ketone by the active species of the enzyme, the high-valent iron-oxo porphyrin species. In general, the computationally discovered mechanism of a porphyrin proton shuttle suggests that there is an enzymatic pathway that converts benzene directly to a phenol and ketone.

A pulse radiolysis study of six parasubstituted benzenediazonium salts is carried out in strongly acidic aqueous solution , where the principal reductant is the hydrogen atom. The characteristics of the corresponding hydroxyl adducts of the diazonium salts are described.

The absolute absorption spectrum of the benzyl radical in the visible region measured by ring-down spectroscopy in the visible region measured by cavity ring-down spectroscopy is presented. The absorption cross sections reported would facilitate the quantification of the benzyl radical in future kinetic studies.

The study presented provides explanations to the addition of the first and the second hydrogen atoms to benzene. The methods used for this purpose are density functional theory and generalized gradient.

Poly(6-azulenylethnyl)benzenes are prepared by a simple one-pot reaction involving repeated Pd-catalyzed alkynylation of halogenated aernes with substituted 6-ethynylazulene and /or ethynylated arenes with substituted 6-bromoazulene. Hexakis(6-azulenylethynyl)benzene exhibited a quasi-reversible broad reduction wave.

The ab initio maximization and electrostatic potentials are calculated for numerous disubstituted benzenes. A considerable six parameter correlation between logP and the calculated descriptors for a training set of representative disubstituted benzenes is presented.

The aromaticity of benzenes annelated to small rings is examined using ab initio molecular orbital calculations. The aromaticity of benzene is explained in terms of the similar electronic states for six pi bonds from the configuration interplay localized molecular orbital CASSCF analysis on the basis of ab initio measurements.

The thin films of a benzylic amide macrocycle, the common component of a wide class of mechanically interlocked molecules, are prepared by vapor deposition on Au(111). The films are characterized by monochromated X-ray photoelectron spectroscopy (XPS) and high resolution electron energy loss spectroscopy (HREELS).

Research has been conducted on the thermal or photochemical ethyl diazoacetate reaction with benzene to produce the isomeric cycloheptatrienes mixture. The details of this reaction are discussed.

BTEX and two chemical warfare simulants, half mustard and dissopropylmethyl phosphonate, are placed in water and adsorbed into fiberglass supported activated carbon filters. Removal of the contaminants, the pressure drops of the filters, and the regeneration of the FGAC filter is graphed.

Research has been conducted on the star- and trefoil-shaped polyethynyl aromatic structures representing all-carbon network graphdiyne model substructures. The synthesis and characterization of these aromatic structures are discussed.

Research is presented concerning the investigation of chromophore aggregation and phenyl group rotation in poly- and oligo-(phenyleneethynylene)s through the use of semiempirical calculations and photophysical measurements.

The electronic structure of benzene adsorbed on single-domain Ge(100-(2*1) and on a single-domain Ge monolayer grown on SDi(100)-(2*1) is investigated by angle-resolved ultraviolet photoemission spectroscopy (ARUPS). The weekly bound benzene species can only be observed on Ge(100) but not on Si(100) or Ge/Si(100) and the reason for this bonding is because it is based on kinetic hindrance of saturation of the chemisorbed species.

A study of the potential energy surfaces (PESs) of the interaction of benzene with Pt and Pt2 with the help of density functional B3LYP computational level using the Ha-Wadt relativistic core potential is presented. The resulting stable structures, which are formed are rationalized in terms of molecular orbital patterns.

The interactions of first-row hydrides with ethene and benzene are investigated with regard to olefinic vs aromatic pi-H interactions.

Research indicates that photocatalytic reduction of halogenated benzene derivatives is possible. As a result, a decrease in toxicity is achieved. Accompanying charts and graphs provide additional statistical data.

A chirooptical switch was developed based on cicularly polarized light with opposite handedness to produce enantiomeric structures.

Lithium and sodium metal in THF-d8 were used to reduce phenyl-perisubstituted benzenes, tretraphenylbenzene and hexaphenylbenzene.

Interactions between the pi face of benzene and ammonia are reported as a model of NH/pi interaction.

Research studying the positional isomers of substituted benzenes is presented. Particular attention is given to the effects of skeletal disubstitution observed on the out-of-plane distortivity. Changes in frequencies of the normal modes are observed.

University researchers investigated the sorption of ionizable organic solutes such as benzene, phenol and aniline on surfactant-modified zeolite.

The CAS MCSCF/CAS MCQDPT2 ab initio method utilizing the 6-31G* basis set was used to study the 1,4-cycloaddition reactions of singlet oxygen with s-cis-1,3-butadiene to form 3,6-dihydrol[1,2]dioxin and to benzene to form 2,3-dioxabicyclo-[2.2.2]octa-5,7-diene.

Results reveal that some electron-deficient enynes can be highly reactive substrates in the palladium-catalyzed homo-benzannulation reactions. Research describes the introduction of functional cyano- alkoxycarbonyl groups to the benzene ring, which aids in an efficient regioselective synthesis of functionalized polysubstituted benzenes.

Research is presented describing the study of cycloalkane solvent holes to determine reversible reactions.

It has been possible to measure powder neutron and synchrotron X-ray diffraction patterns from zeolite ZSM-5 containing levels of adsorbed benzene of around 3.4 molecules per unit cell and 7.6 molecules per unit cell.

A 2H NMR study on clathrates with a polycyano-polycadmate host is presented. A number of models of guest molecular motions are suggested based on their molecular and crystal structures.

The many ways in which the scanning tunneling microscope (STM) can investigate the adsorption and unimolecular reaction of unsaturated six-membered ring molecules are discussed. The STM can prompt a chemical reaction and characterize the initial and final states on the atomic scale.

Research is presented describing the mapping out of the vibronic energy levels in the S1(pi,pi*) electronic excited state, via the laser-induced fluorescence spectra and electronic absorption spectra of supersonic-jet-cooled 1,3-benzodioxole molecules.

Research is presented describing the use of time-resolved spectroscopy to study fluorescent quenching of two azoalkanes by several aliphatic amine donors in benzene.

Experiments on the absorption of toluene, 0-xylene and benzene to wood are described. The results could be used to help predict organic contaminant transport at landfills, which often contain up to 25% wood waste by weight.

Study of the effects of airflow rate, air channel spacing, and porous media type on NAPL removal, using a lab-scale reactor with vertical air channels. Increased channel spacing caused the NAPL removal efficiency to decrease.

Issues concerning the role of potential CO2/F intermolecular interactions in solution are considered. This research involved measuring the T1 values of perfluorobenzene, benzene and perdeuteriobenzene in CO2 as a function of temperature and pressure.

It has been possible to analyze the reaction pathways and the energetics for the direct hydroxylation of methane and of benzene that arise on the surface of Fe-ZSM-5 zeolite. The 'two-step concerted mechanism' should be widely used in analyzing how hydrocarbon hydroxylations are catalyzed by transition-metal oxides.