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

Photochromic systems can convert light energy into mechanical energy, thus they can be used as building blocks for the fabrication of prototypes of molecular devices that are based on the photomechanical effect. Hitherto a controlled photochromic switch on surfaces has been achieved either on isolated chromophores or within assemblies of randomly arranged molecules. Here we show by scanning tunneling microscopy imaging the photochemical switching of a new terminally thiolated azobiphenyl rigid rod molecule. Interestingly, the switching of entire molecular 2D crystalline domains is observed, which is ruled by the interactions between nearest neighbors. This observation of azobenzene-based systems displaying collective switching might be of interest for applications in high-density data storage. scanning tunnel microscopy | molecular switches | photochromic system | data storage

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.

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.

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 threshold photoelectron spectrum of benzene has been recorded up to 26.5 eV photon energy under high-resolution conditions using synchrotron radiation and employing the penetrating-field threshold electron collection method. By means of a direct comparative study with a recent HeI pbotoelectron spectrum of benzene of equally high resolution, numerous autoionization effects are observed in the formation of the ionic band systems of benzene in the outer valence ionization region in the threshold photoelectron spectrum. The Rydberg states responsible for these effects are identified. Autoionization does not appear to play a role in the formation of the two lowest-energy, innervalence bands of [C.sub.6][H.sup.+.sub.6]. Key words: threshold photoelectron spectroscopy, photoelectron spectroscopy, benzene, ionization, autoionization, Rydberg states.

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.

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.

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.

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 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).

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.

m- or p-diiodobenzene undergoes selective double coupling reactions with arylboronic acids and esters. Results show that diiodobenzenes are the best choice of electrophile if double coupling is desired, whereas selective coupling can be obtained through reactions of dibromobenzenes with arylaboronic acids.

The X-ray analysis of bis(p-fluorophenyl)methyl cation bearing a 2,6-bis(p-substituted phenyloxymethyl)benzene ligand show a symmetrical structure (10-C-5) where the two C-O distances are identical. The electron distribution analysis by accurate X-ray measurements and the density functional calculation on the bis(p-fluorophenyl)methyl cation show that the central carbon atom and the two oxygen atoms are bonded.

In situ synchrotron X-ray powder diffraction patterns of porous coordination polymers are measured. Adsorption of benzene in the channels inducted a remarkable contraction in the crystal although the channels were occupied by the benzene molecules.

The synthesis of calixarenes where one or more of the benzene rings are formed convergent with the annulus is described. The overall yields from commercially available materials of the unsymmetrical calixarenes so generated are comparable with the overall yields of existing methods via the different strategies.

The synthesis of a range of octopolar 1,3,5-tri(esthynylphenyl)benzenes through Sonogashira link is explained. The productiveness of chemically tuning the target products is demonstrated where absorption and discharge properties could be suitably designed.

Room temperature reaction of C(sub 6)F(sub 6) with 29 transition metal ions is studied using inductively coupled plasma (ICP) selected ion flow tube tandem mass spectrometer. It is reported that the trends across the periodic table suggests a correlation between electronic configuration of the reaction path and reaction efficiency.

Selectively excited benzene and toluene in the gas and solution phase are investigated with ultrafast transient absorption spectroscopy to study the impact of a solvent on the time scales of intramolecular vibrational energy redistribution (IVR). The findings indicate that an internal rotor accelerates IVR in the gas phase significantly whereas the effect appears to be largely concealed in solution.

HM-IE was tested for interaction energies of Ne2, (C2H2)(sub 2), and N2-benzene for many orientations sampling the entire potential energy surface. It was found to be in excellent agreement with the CCSD(T)LBS results while requiring considerably less computational time and resources.

The photophysical and photochemical properties of some aza-analogues of 1,4-distyrylbenzene, bearing a nitrogen heteroatom in the side arene rings are investigated. By selective photoexcitation, information about the conformational equilibria of the compounds bearing side quinolyl groups or the pyridyl central ring, due to internal rotation around the quasi single bonds with the ethenic carbons was obtained.

A spectroscopy study of the van der Waals complex between benzene and hexafluorobenzene formed in liquid krypton solutions is reported. It is suggested that the interaction energy of arenes with fluorinated arenes in solution is substantially smaller than that of a typical hydrogen bond and would not be expected to result in persistent structural features in solution.

The isotopmer selected N = 2 CH chromophore absorption of (super 12)C(sub 6)H(sub 6) and (super 13)C(super 12)C(sub 5)H(sub 6) near 6000 cm(super -1) at natural abundance are recorded. The (super 12)C(sub 6)H(sub 6) spectrum is compatible with a proposed model of intramolecular vibrational redistribution with a distinct hierarchy of time scales.

Rotationally resolved fluorescence excitation spectra of the N2 van der Waals complex of p-difluorobenzene (pDFB-N2) are recorded in the collision free environment. The data obtained provide information about the structure and internal motion of pDFB-N2 in its ground (S0) and excited (S1) electronic states.

Rotationally resolved fluorescence excitation spectra of the N2 van der Waals complex of p-difluorobenzene (pDFB-N2) are recorded in the collision free environment. The data obtained provide information about the structure and internal motion of pDFB-N2 in its ground (S0) and excited (S1) electronic states.

The solvent dependence of absorption and fluorescence spectra, fluorescence lifetimes, and quantum yields of various 3-substituted benzanthrone derivatives were investigated. The rate constant and efficiency of intersystem crossing between fluorescent excited state and upper triplet state were strongly influenced by the substituent and by the solvent polarity.

The cation and anion products of the reactions between lead clusters produced in the laser ablation and the benzene molecules seeded in argon are studied by high-resolution reflectron time-of-flight mass spectrometer (RTOFMS). Two conspicuously different and independent reaction mechanisms for lead cluster cations and anions are proposed.

The true catalyst in the benzene hydrogenation system beginning with Ru(II)(eta6-C6Me6)(OAc)2 as the precatalyst is investigated. It is concluded that the true catalyst is bulk ruthenium metal particles, and not a homogeneous metal complex or a soluble nanocluster. The procedures leading to this conclusion are detailed.

Ab initio and density functional calculations are used to study the structures and thermochemical properties of the benzene-OH adduct (hydroxycyclohexadienyl, CHD-OH). The rate constant for CHD-OH adduct dissociation to C6H6 + OH are calculated and compared to literature data.

The uptake by 1-octanol of gas-phase alpha-pinene, gamma-terpinene, p-cymene, and 2-methyl-2-hexanol are measured as a function of relative humidity and temperature (263-293 K) with the use of droplet train apparatus. Uptakes of the gas-phase species benzene, H2O, SO2, and H2S are also studied.

Photodissociation of both fluorobenzene and d5-fluorobenzene at 193 nm under collision-free conditions is studied in separate experiments using multimass ion imaging techniques. Findings show that the potential energy surface obtained from ab initio calculations indicates that the four-center reaction in the ground electronic state is the major dissociation mechanism for the HF and DF eliminations.

Accurate geometries and harmonic force fields for trans- and cis-azobenzene determined by second-order Moller-Plesset perturbation theory is reported. Both isomers report UV spectra calculated using the second-order approximate couple-cluster singles-and-doubles model CC2 with accurate basis sets.

The amino groups of the mesoporous MCM-41 solids are used to immobilize (VO)(super 2+) ions for studying the catalytic oxidation of benzene. It was found that the vanadium peroxo complex of V(super 5+)-O-O(super .) radicals play an important role in the hydroxylation of aromatic hydrocarbons, such as from benzene to phenol.

The dehydrogenation of benzene on Pt/ZnO(0001)-O model catalysts was studied with temperature-programmed desorption (TPD) and low-energy ion scattering spectroscopy (LEIS). The LEIS signal suggests that approximately one-third of the adsorbed c-C6D6 on the Pt islands also desorbs molecularly at ~300-480 K.

The calculations on free base tetraphenylporphyrin (H2TPP) in benzene solution using fluorescence up-conversion and transient absorption are presented. A model for explaining the primary intramolecular processes in the Soret, Qy and Qx electronic complexes with specific sequence of time scales and couplings is described.

The threshold photoelectron-photoion coincidence spectroscopy is used to analyze the dissociation dynamics of the bis(benzene) chromium ion, (C6H6)(sub 2)Cr(super +). The two benzene loss reactions are found to be metastable at photon energies near the dissociation boundaries of the precursor ions.

The mono and bis-adducts of benzene of the kind M(C6H6)(sub 1,2)(super +) are obtained in the gas state with first, second and third row transition metal cations and their sensitivities toward molecular oxygen are studied. It is observed that the molecular oxygen activation by early transition metal cations is conserved in the presence of one benzene molecule but ceases in presence of two molecules.

A novel 'site decompression technique' was applied in a spectroscopic investigation of 3-fluoro-o-benzyne and perfluoro-o-benzyne compounds, resulting in virtually background-free, complete, high-resolution IR sepctra with line widths of ca. 0.1 cm(super -1). It is recommended that this technique is having great potential for solid-phase spectral studies of reactions that are accompanied by volume changes and enables the observation of weak transition that would otherwise easily escape detection.

A new biosynthetic pathway to synthesize benzene-free aromatic chemicals, such as pyrogallol, hydroquinone and resorcinol, involving intermediacy of polyhydroxyaromatics derived from glucose is discussed. The strategy employs catalytic hydrogenation of polyhydroxynbenzenes followed by acid-catalyzed dehydration of the dihydro intermediates, which results in loss of an oxygen atom from the starting polyhydroxybenzene.

The reorientational motion of benzene is examined in the neat liquid and in a polystyrene/benzene solution, which was, investigated by NMR relaxation as well as MD simulation methods. It is concluded that the rotations about the C(sub 6) axis were much faster than about axis perpendicular to the C (sub 6) axis and this finding is in accordance to a previous MD study by Muller-Plathe.

Branching ratios for the reactions are examined of 1-butene, 1,3-butadiene, and benzene with stoichiometric tantalum oxide clusters. It is concluded that the major reaction channel of most of these clusters involves loss of molecular oxygen to form the smaller, more stable stoichiometric clusters, which then proceed to react with or associate the hydrocarbon gas.

A general method is described for the copper-catalyzed arylation and alkenylation of polyfluorobenzene C-H bonds. The results are obtained by using a combination of copper iodide catalyst, phenanthroline ligand, aryl bromide or aryl iodide coupling partner, and DMF or DMF/xylene mixed solvent.

Variable temperature studies of fluorescence of two groups of substrates to probe the reactivity of the anisole isomers as compared to the benzonitriles are presented. It is concluded that the effect of temperature on fluorescence is an important tool for studying the reactivity of excited singlet state of substituted benzenes.

Neutral Pt(II) complexes of unsymmetrical 2-(N-arylimino)pyrrolide ligands which are easily synthesized are reported. Two types of nitrogen ligation with widely different steric and electronic attributes are also presented.