DFT modeling of sandwich complexes involving cationic palladium chains and polyenic or polycyclic aromatic hydrocarbons

DFT calculations are reported on a series of one-dimensional palladium complexes with general formula [Pd(m)(C(2n)H(2n+2))(2)](2+) (m = 2-4, n = 2-8, n > or = m), in order to model and analyze the bonding in the series of organometallic sandwich compounds recently reported by the group of T. Murahashi and H. Kurosawa. The bonding interactions are elucidated, and the frontier orbitals involved are described as a function of the haptotropic conformation of the metal atoms, either di-hapto or tri-hapto. In both cases, the driving force to the complex organization is a strong donation interaction from the pi system of the hydrocarbons to an orbital with appropriate phase and composition, delocalized over the metal chain, and depopulated by the double oxidation process. No net bonding interaction can be characterized along the metal string, and the metal-metal distances are mainly governed by the hapticities of adjacent atoms. The energy associated with the formation of a complex is calculated with respect to its fragments, assumed either isolated or solvated. The results emphasize the stabilizing role of a large delocalization of the positive charge transferred to the hydrocarbons. This delocalization extends to the hydrocarbon regions not directly in contact with palladium and highlights the importance of these "inactive" regions in complexes made from diphenyl polyenes or polycyclic aromatic hydrocarbons. Finally, the bonding pattern deduced from calculations has been utilized to consider the feasibility of novel sandwich architectures, whose computed energy balance eventually proves similar to that of already existing compounds.     

官能团化稠环芳香烃合成进展

对稠环芳香烃的合成方法、官能团化稠环芳香烃最新合成进展、官能团化稠环芳香烃构建的复杂分子体系(液晶、刚性线型和环状的大分子)及其超分子化学进行了评述.     

Synergistically Directed Assembly of Aromatic Stacks Based Metal‐Organic Frameworks by Donor‐Acceptor and Coordination Interactions

A synergistically directed assembly approach to distinctive metal‐organic frameworks utilizing both donor‐acceptor (D‐A) interaction from aromatic systems and coordination interactions is presented. Based on such an approach, the coronene‐tpt (tpt = 2,4,6‐tri(4‐pyridyl)‐1,3,5‐triazine) stacks based coronene‐MOF‐1 — 4 have been successfully fabricated. Their structural discrepancies with coronene‐ absent control products, 1′ — 4′ , illustrate clearly the significance of coronene‐tpt based D‐A interactions in these architectures. All these coronene‐MOFs contain varied coronene‐tpt stacks as organic secondary building blocks (SBUs), which are closely interrelated with the coordination based framework structures. Moreover, porous coronene‐MOF‐1 and ‐2 exhibit high physicochemical stability and significant light hydrocarbons storage and separation performances.     

Study on retention behavior of peropyrene-type polycyclic aromatic hydroccrbons with various bonded stationary phases in reversed-phase liquid chromatography

Summary The retention behavior of 15 peropyrene-type polycyclic aromatic hydrocarbons was investigated on various bonded stationary phases in reversed-phase liquid chromatography. On diphenyl and naphthylethyl bonded phases, high correlations were obtained between the molecular polarizability of solutes and their retention. However, very low or no correlations were found on various octadecyl bonded phases. These facts are discussed by using the electrostatic interaction concept between the solutes and the stationary phase. We conclude that these observations are due to two reasons: the difference in the degree of planarity of polycyclic aromatic hydrocarbons and the high ability of planarity recognition of octadecyl bonded phases.     

Molar excess volumes of furfuryl alcohol and aromatic hydrocarbons at 25°C

Molar excess volumes of mixing V^E for binary mixtures of furfuryl alcohol with the aromatic hydrocarbons benzene, toluene, ethylbenzene, and o-, m-, and p-xylene were determined for the entire composition range at 25°C. V^E was negative for the mixtures containing benzene, toluene and pxylene but positive for mixtures containing ethylbenzene and o- and m-xylene. The results are discussed in terms of specific interaction present in the binary mixture and are compared with those previously reported for tetrahydrofuran, fur an or furfural binary mixtures with aromatic hydrocarbons.     

Synthese und EPR-spektroskopie phenyl-substituierter und teildeuterierter schlenk'scher kohlenwasserstoffe

The synthesis of several phenyl-substituted and partially deuterated Schlenk's hydrocarbons and of deuterated tetracyclones is described. The paramagnetic species exhibit strong EPR triplet powder spectra on account of the dipolar interaction between the unpaired spins. The influence of substitution and of deuteration on the magnitude of the zero field splitting parameters is discussed. The molecular conformations giving the best fit to the experimental results are examined.     

Coronenes,Benzocoronenes and Beyond: Modern Aspects of Their Syntheses,Properties, and Applications

In recent years, a variety of new designs of coronene-based polycyclic aromatic hydrocarbons (PAHs) with diverse functions have emerged to serve as complementary materials in organic chemistry and materials chemistry. In the present review, we highlight the modern aspects of syntheses related to or different from the strategies used in the early era of coronene research. Systematic extension and expansion of coronene backbones to wide categories of angular PAHs are covered. The substitution and extension of coronene architectures, by incorporating functional groups and by fusing small and large conjugated units, advatangeously enrich their photophysical, electrochemical, self-assembling, and other properties, of which are discussed to demostrate their impact in materials chemistry. While the highly symmetric coronenes, tribenzocoronenes and hexabenzocoronenes conceived wide potential in charge-transporting, electroluminescent, sensing, and other applications, other related derivatives such as dibenzo, tetrabenzo and pentabenzocoronenes also displayed their potentials as exemplified by their use as charge-conduction channel in transistor application.     

Extension of the A-UNIFAC model to mixtures of cross- and self-associating compounds

In the present work an extended UNIFAC group contribution model is used to calculate activity coefficients in solutions containing alcohols, water, carboxylic acids, esters, alkanes and aromatic hydrocarbons. The limiting expressions for the association contribution to the activity coefficients at infinite dilution are presented and discussed. A new set of interaction parameters between associating and non-associating functional groups is reported. This set of parameters is applied in the association model to predict vapor–liquid, liquid–liquid equilibrium and infinite dilution activity coefficients.     

Differential calorimetric study of polycyclic aromatic hydrocarbons

The temperature, enthalpy, entropy of melting and crystal transitions of 21 polycyclic aromatic hydrocarbons, containing from 2 to 6 unsubstituted condensed rings, were determined by differential scanning calorimetry. The temperature and the molar entropy of melting generally increase with increasing degree of symmetry and molecular size of the hydrocarbon. Apparent deviations from this trend are discussed in terms of molecular distorsion due to steric interaction between neighbouring hydrogens.     

Regularities in the retention of isomeric aromatic hydrocarbons in liquid chromatography. Part I. Analysis of polymethyl-and monoalkyl benzenes and polynuclear aromatic hydrocarbons on hydroxylated silica gel

Summary The retention on hydroxylated silica gel surface upon elution with n-hexane increases in the series of polymethylbenzenes and decreases in the series of mono-alkylbenzenes (after toluene) All iosmers of xylenes, trimethyl- and tetramethylbenzenes are separated as well as isomers of tert.-phenyls, isomers of several dimethylnaphthalenes, anthracene, phenanthrene and poly aromatic hydrocarbons with five condensed rings. These separations are based on the influence of the corresponding molecule structures on the intermolecular interaction with both the adsorbent (strengthening or weakening the energy of hydrogen bonds) and the eluent (intermolecular interaction with n-hexane increases upon lengthening the alkyl group). The effect of orientation at the surface of the investigated hydrocarbon molecules on their retention is also discussed.     

A parallel architecture and programming language for quantum chemistry

The large gains in computational capability which are required in the future by problems in computational quantum chemistry must come from advances in both parallel architectures and algorithms. The relation between algorithms and architecture is discussed, with examples of non-numerical algorithms for which future architectures should facilitate implementation. The use of timespace complexity trade-offs is discussed. A parallel language extension and architecture targeted towards general numerical and nonnumerical algorithms being developed by Myrias Research Corporation is briefly presented.     

A comparison of potential molecular wires as components for molecular electronics

The field of electronics using single-molecule components has recently received much attention as a possible new design concept for the continued miniturisation of electronics. Molecular wires are the conceptually simplest components of such electronic systems and several different compound types have been used to produce molecular wires. Examples of some of the most promising families of molecular wires are presented, namely conjugated hydrocarbons, carbon nanotubes, porphyrin oligomers and DNA. Discussion centres around their potential use in functioning electronic architectures in terms of their electronic properties, ease and controllability of synthesis and potential for self-assembly.     

Some solvent effects on the solvent extraction of 8-quinolinol

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order. Among the solvents studied, chloroform shows significantly higher values than expected; the deviation may be explained as a specific interaction of the hydrogen- bonding type.     

Hybrid Nanomaterial Architectures: Combining Layers of Carbon Nanowalls,Nanotubes, and Particles

The paper focuses on the integration in hybrid architectures of plasma produced nanomaterials. The routes for the fabrication of layered structures consisting of carbon nanowalls on carbon nanotubes (CNW/CNT), of carbon nanotubes on carbon nanowalls (CNT/CNW), and nanoparticles on carbon nanowalls (NP/CNW) are presented. The morphology and structure of the hybrid architectures were investigated by electron microscopy techniques. We show that higher substrate temperature promotes the formation of high mass hydrogenated carbon clusters which favors the dominance of CNW growth over that of CNT. On this basis, a procedure of obtaining CNT/CNW architectures by switching the growth regime via substrate temperature is described. The specific limitations or advantages concerning the control or the properties of the obtained architectures are discussed.     

Orbital views of molecular conductance perturbed by anchor units

Site-specific electron transport phenomena through benzene and benzenedithiol derivatives are discussed on the basis of a qualitative Hu?ckel molecular orbital analysis for better understanding of the effect of anchoring sulfur atoms. A recent work for the orbital control of electron transport through aromatic hydrocarbons provided an important concept for the design of high-conductance connections of a molecule with anchoring atoms. In this work the origin of the frontier orbitals of benzenedithiol derivatives, the effect of the sulfur atoms on the orbitals and on the electron transport properties, and the applicability of the theoretical concept on aromatic hydrocarbons with the anchoring units are studied. The results demonstrate that the orbital view predictions are applicable to molecules perturbed by the anchoring units. The electron transport properties of benzene are found to be qualitatively consistent with those of benzenedithiol with respect to the site dependence. To verify the result of the Hu?ckel molecular orbital calculations, fragment molecular orbital analyses with the extended Hu?ckel molecular orbital theory and electron transport calculations with density functional theory are performed. Calculated results are in good agreement with the orbital interaction analysis. The phase, amplitude, and spatial distribution of the frontier orbitals play an essential role in the design of the electron transport properties through aromatic hydrocarbons.     

GROWTH AND MORPHOLOGY OF POLYMER-ACTIN COMPLEXES

F-actins are semi-flexible polyelectrolytes and can be assembled into large polymer-actin complex with polymorphism through electrostatic interaction with polycations. This study investigates the structural phase behavior and the growth of polymer-actin complexes in terms of its longitudinal and lateral sizes. Our results show that formation of polymer-actin complexes is cooperative, and morphology and growth of polymer-actin complexes depend on polycation species and concentrations of polycation and salt in a constant actin concentration. We found that the longitudinal growth and lateral growth of polymer-actin complexes are dominated by different factors. This induces the structural polymorphism of polymer-actin complexes. Major factors to influence the polymorphism of polymer-actin complexes in polyelectrolyte system have been discussed. Our results indicate that the semi-flexible polyelectrolyte nature of F-actins is important for controlling the morphology and growth of actin architectures in cell.     

Long term nonmethane hydrocarbon and halogenated hydrocarbon measurements at three West German sampling sites

Summary Results of a long time series of nonmethane hydrocarbons and halogenated hydrocarbons measurements at three differently polluted sites in the FRG are presented. The question discussed is to what extent the observed seasonal cycles can be explained by variations in sources and sinks.     

Detection and measurement of volatile hydrocarbons at ambient concentrations in the atmosphere

Modern techniques for the sampling and analysis of volatile hydrocarbons present at ppm-ppM levels in air are reviewed. Emphasis is placed on methods designed to detect and determine individual hydrocarbons of particular interest. Advances in instrumentation and automation are discussed with particular reference to systems combining gas chromatography, mass spectrometry and computerized data-analysis.     

ELECTROGENERATED CHEMILUMINESCENCE OF SEVERAL POLYCYCLIC AROMATIC HYDROCARBONS

Abstract Electrogenerated chemiluminescence (eel) of several polycyclic aromatic hydrocarbons (PAH) (-)/triphenylamine (TPA) derivative (+) mixed systems has been studied at a platinum wire electrode in acetonitrile (ACN) and tetrahydrofuran (THF) solutions using tetra- n -butylammonium perchlorate (TBAP) as a supporting electrolyte, and the results are reported. Exciplexes, as well as the lowest singlet excited state of PAH, are identified as emitting species in these eel systems. The results shown by the temperature and pulse duration dependencies on eel intensities indicate that exciplexes are formed directly from solvent separated ion pairs. The interaction of PAH in their excited states with several donor molecules is discussed based on eel and fluorescence quenching results.