Fused multifunctionalized bridge aromatic hydrocarbons from in situ-generated arynes and anthracene derivatives

This study presents a facile strategy for the formation of highly substituted butterfly 1,4-adducts/9,10-adducts via the Diels–Alder reaction of benzyne intermediates. The method achieves very good to excellent yields of the respective anthracene derivatives under mild conditions. This practical protocol is compatible with a variety of sensitive functional groups and provides access to difunctionalized bridge 1,4-adducts/9,10-adducts.     

A new suzuki-heck-type coupling cascade: indeno[1,2,3]-annelation of polycyclic aromatic hydrocarbons

Under palladium catalysis, o-bromobenzeneboronic acid can be coupled with 1-bromonaphthalene (6) and with oligocyclic bromoarenes to furnish indeno-annelated polycyclic aromatic hydrocarbons 1-4 and 25 in a single operation in moderate to good yields (27-87%). Alternatively, o-dibromoarenes and 1,2-dibromocycloalkenes can be cross-coupled with 1-naphthaleneboronic acid under the same conditions to yield analogous products (6-87%), and indenocorannulene (19) can be prepared likewise in a single step from pinacol corannuleneboronate (18) (40%).     

Carcinogenicity of polycyclic aromatic hydrocarbons: A dialogue

A discussion between a biochemist and a theoretical chemist reviews the insights that quantum chemistry brings to polycyclic aromatic hydrocarbon carcinogenicity. Limitations as well as successes of the theory are described. The importance of communication between theorists and experimentalists in this complicated field is emphasized.     

Experimental and theoretical investigation of radiative lifetimes in neutral gallium

Using laser spectroscopic techniques the natural radiative lifetimes of 4s ² n ₁ s ² S and 4s ² n ₂ d ² D states of neutral gallium have been measured forn ₁ = 6 to 11 andn ₂ = 4 to 9. These states, as well as previously measured4s ² np ² P states, have been investigated theoretically using multi-configuration Hartree-Fock calculations. Oscillator strengths to all lower-lying states have been calculated and theoretical lifetimes of the investigated states evaluated. The² D sequence is strongly influenced by the 4s4p ^{2 2} D perturber, and strong cancellation effects in the radiative decay are observed both theoretically and experimentally.     

The influence of iodide ions on the radiative and radiationless decay of the triplet state of aromatic hydrocarbons

An analysis of the influence of I^? ions on radiative and radiationless transitions from the lowest triplet state of aromatic hydrocarbons is presented. The distance dependence in the external heavy atom effects and the dependence of the enhancement of the T₁→S₀ radiative transition on the triplet energy is discussed in terms of perturbation theory.     

Measurement of excitation functions and radiative lifetimes of oxygen ions

Oxygen ions from a 2 MV tandem accelerator have been used in beam-foil spectroscopic studies of O II, O III and O IV in the wavelength region 2000–5000 Å. Excitation functions for relative level populations in O II, O III and O IV in the incident energy range of 1.2–3.75 MeV have been measured and interpreted in terms of the independent electron model. Mean radiative lifetime measurements for a number of levels including cascades 4631 Å feeding to 2450 Å and 4344 Å feeding to 2385 Å in O IV have resulted in consistent values. Lifetime measurements for some of the O II levels of astrophysical interest have been reinvestigated and significant deviations from earlier values were observed.     

Microheterogeneity evaluation of polycyclic aromatic hydrocarbons in particulate standard reference materials

With the emergence of highly sensitive analytical techniques, the microanalysis of natural-matrix materials employing smaller sample sizes is increasingly more common, which subsequently warrants a homogeneity assessment for the individual components at the appropriate sampling level. Pressurized liquid extraction (PLE) in combination with gas chromatography/mass spectrometry (GC/MS) has been used to determine the sampling constants and evaluate the relative homogeneity of trace levels of polycyclic aromatic hydrocarbons (PAHs) for two previously certified particulate standard reference materials, SRM 1649a Urban Dust and SRM 1650b Diesel Particulate Matter, in the milligram sampling range. Fluoranthene, pyrene, benz[a]anthracene and benzo[e]pyrene within SRM 1650b Diesel Particulate Matter were deemed to be homogeneous, based on relatively small sampling constants (K _S<100 mg), whereas the larger sampling constants (K _S>100 mg) obtained for all PAHs in SRM 1649a Urban Dust suggest more material heterogeneity. The material heterogeneity of ten individual PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene) was also described via nonlinear relationships (i.e., power law) between subsampling error S _s (%) and sample mass, which are used to predict analyte-specific minimum sample masses that result in a specific level of analytical uncertainty. Electronic supplementary material Supplementary material is available for this article at and is accessible for authorized users.     

Electronic structure of saturated hydrocarbons in the semiempirical equivalent orbital method

The problem of matrix elements of the Hartree-Fock Hamiltonian for saturated hydrocarbons in the EO method is considered. It is stated, that all the proposed scales of such parameters are incomplete or lead to an incorrect band structure of diamond. It is shown that the data on the band structure of diamond may be useful to obtain the full scale of the parameters for the calculations of the electronic structure of hydrocarbons.     

Natural radiative lifetimes in the 5snd 1 D 2 series of SrI

Natural radiative lifetimes have been measured for the 5snd ¹ D ₂ series in SrI for the previously not measuredn=10, 11 and 12 states. The measurements connect earlier measurements in lower and higher states in this heavily perturbed series. The lifetimes were determined using pulsed laser excitation and time-resolved detection.     

Oxidative polymerization of aromatic hydrocarbons: A study of kinetics and mechanism

Aromatic hydrocarbons were homopolymerized by means of an oxidative polymerization reaction with the use of the catalyst system anhydrous aluminum chloride–cupric chloride. The kinetics of the benzene homopolymerization carried out under different experimental conditions was followed by the determination of the amounts of cuprous ion and polymeric product formed in the reaction. Cuprous ion was spectrophotometrically titrated in the form of its complex with 2,2′-biquinolyl (cuproine). The experimental results do not agree with cationic mechanism for this reaction previously proposed in the literature. Ethylbenzene was kinetically studied under the same experimental conditions. In view of the experimental evidences obtained in this work and on some literature data, a mechanism based on formation of cation-radicals is proposed for the oxidative polymerization reaction when carried out under the studied conditions.     

Aliphatic and aromatic hydrocarbons in the mediterranean aerosol

The atmospheric transport of organic pollutants over long distances and their effect on the biological cycles of the sea are two major questions of concern in environmental chemistry. These processes are of particular importance in the Mediterranean Sea because of its semi-enclosed characteristics, which determine the accumulation of the pollutants entering into the system. In order to get some insight into these processes a project (PHYCEMED), was developed for the evaluation of the atmospheric budget of organic and inorganic substances in the Western Mediterranean and for the investigation of the exchange mechanisms of these materials across the air/sea interface. A high volume air sampling system including a cascade impactor was placed on board of the R/V le Suroit for collecting the aerosols along several transects parallel to the French, Spanish and North-African coasts, facing areas of different population densities and industrial activities. The cruise was realised on October 1983 and the particulate material was fractionated into the following sizes: 7.2, 3.0, 1.5, 0.96, and 0.03 micron. Quantitative and qualitative analyses of the aliphatic and the aromatic hydrocarbons present in these fractions were performed by high resolution gas chromatography and gas chromatography-mass spectrometry.     

Theoretical and experimental studies of radiative lifetimes of excited electronic states in CO

The electronic dipole transition moment functions of the A ²Π-X ²Σ⁺, B ²Σ⁺-X ²Σ⁺ and B ²Σ⁺-A ²Π transitions and the dipole moment function of the X ²Σ⁺ state of CO⁺ have been calculated using large contracted CI wavefunctions. The computed transition moment functions together with experimental potential energy curves were used to obtain radiative lifetimes of the excited electronic states B ²Σ⁺ and A ²Π. Radiative lifetimes of vibrational levels of the X ²Σ⁺ state were derived from the calculated dipole moment function. The high-frequency deflection technique was used to obtain radiative lifetimes of the ν′ = 0, 1,2 and 3 vibrational levels of the B ²Σ⁺ state and also radiative lifetimes of individual rotational levels of ν′ =0. The calculated radiative lifetimes are shorter than the measured ones by about 10%. The experimental ν′ dependence is reproduced by theoretical calculation. The calculated radiative lifetimes for the A ²Π state are in excellent agreement with lifetimes measured with an ion trap technique.     

Quenching of anthracene fluorescence by dialkylanilines in saturated hydrocarbons

The bimolecular quenching constants of anthracene fluorescence by dialkylanilines in saturated hydrocarbons depend on the solvent viscosity and may exceed theoretical diffusion controlled limit in viscous hydrocarbons.     

On the determination of radiative lifetimes of excited Mn I and Mn II levels

Time-resolved laser-induced fluorescence spectroscopy has been used to measure the lifetimes of 46 Mn I and 7 Mn II levels. A high-current hollow cathode produces an effusive beam of manganese atoms and ions in the ground states and in metastable states. Selected states are populated with tunable dye laser pulses. The following fluorescence is measured by means of a Tektronix 1 GHz transient digitizer. Including the separately measured response function of the system in the evaluation procedure the full decay curve can be applied for a determination of the lifetimes. All measurements are performed with linearly polarized laser beams adjusted to the magic angle in order to exclude systematic error sources. A comparison with literature data is given.     

Residential wood combustion: A source of atmospheric polycyclic aromatic hydrocarbons

Samples were taken of the atmospheric particulate matter over Fairbanks Alaska in the winter of 1985, and from wood stoves burning the major wood types locally available. These samples were then analyzed for polycyclic aromatic hydrocarbon (PAH). A PAH emission profile was determined from the wood stove samples and applied to the atmospheric samples to determine the residential wood combustion contribution to the local atmospheric particulate burden. Emission profiles for coal burning and automobile emissions for PAH were also used to estimate their relative contributions.     

Investigations of radiative lifetimes in the 3p5p configuration of neutral silicon

Lifetimes for the³ S ₁,³ P _{0, 1, 2} and³ D _{1, 2, 3} states in the 3s ²3p5p configuration of silicon have been determined using stepwise dye laser excitation and time resolved detection. A comparison is made with theoretical values, calculated using multi-configuration Hartree-Fock wavefunctions. Laser-evaporation was used to produce free silicon atoms by focusing a Nd: YAG laser on a rotating silicon target.     

Polycyclic aromatic hydrocarbons in the graphene era

Polycyclic aromatic hydrocarbons(PAHs) have been the subject of interdisciplinary research in the fields of chemistry, physics,materials science, and biology. Notably, PAHs have drawn increasing attention since the discovery of graphene, which has been regarded as the "wonder" material in the 21 st century. Different from semimetallic graphene, nanoscale graphenes, such as graphene nanoribbons and graphene quantum dots, exhibit finite band gaps owing to the quantum confinement, making them attractive semiconductors for next-generation electronic applications. Researches based on PAHs and graphenes have expanded rapidly over the past decade, thereby posing a challenge in conducting a comprehensive review. This study aims to interconnect the fields of PAHs and graphenes, which have mainly been discussed separately. In particular, by selecting representative examples, we explain how these two domains can stimulate each other. We hope that this integrated approach can offer new opportunities and further promote synergistic developments in these fields.     

Programming package for semiempirical determination of vibronic radiative transition probabilities in diatomic molecules

Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 2, pp. 188–189, March–April, 1989.     

Application of semiempirical MO calculations to the interaction of hydrocarbons with zeolites

In order to support previous spectral studies and normal coordinate analysis data, the semiempirical SCC-Xα method has been applied to the interaction of propene and cyclopropane with Ca²⁺ ions in front of the sixford windows connecting the sodalite units and the supercages in faujasites and A-type zeolites. From preliminary results, the ion can be approached by propene in a geometry intermediate between parallel or perpendicular orientation of its molecular plane normal to the double bond, while in case of cyclopropane an edge-on interaction seems to be favoured.