Fused Benzene Rings Research Articles

Self-assembled multicolor nanoparticles based on functionalized twistacene dendrimer for cell fluorescent imaging

A series of twistacene-functionalized dendrimers were successfully synthesized and characterized. The model molecule DBPy has a twisted configuration with a torsional angle of 27.69° between pyrene and naphthalene units. The resulting compounds TPPh, TTPy, OTPy and TOPhP can self-assemble into organic nanoparticles through re-precipitation method and emit strong blue, cyan, green and red fluorescence in water, respectively. Additionally, the obtained multicolor nanoparticles showed low cytotoxicity and good photostability that selectively flow into the membrane and cytoplasm of HeLa cells, indicating the feasibility and efficiency in fluorescence imaging. This study might be a new avenue for the design of three-dimensional branched conjugated molecule and specific location imaging in living cell. Chinese researchers have developed a three-dimensional probe with tunable fluorescence emissions for improved imaging of living cells. Dendrimers are emerging polymer materials that grow into globular spheres through a branching process. Jinchong Xiao from the Hebei University and Shu Wang from the Beijing National Laboratory for Molecular Sciences and co-workers conjectured that combining the soft material properties of dendrimers with ‘twistacenes’ — a series of fused benzene rings that controllably emit light — could generate versatile imaging probes with greater affinity for intracellular positions. By tweaking molecular structures and self-assembling the dendrimers into larger organic nanoparticles in water, the researchers synthesized different probes with strong blue, cyan, green and red fluorescence emissions. Cell-based experiments revealed that the team's conjecture was correct: multicoloured nanoparticles were imaged as selectively entering HeLa cell membranes and cytoplasms while displaying minimal cytotoxic side-effects. A series of twistacene-functionalized dendrimers were successfully synthesized and characterized. They can self-assemble into organic nanoparticles through re-precipitation method and emit blue, cyan, green and red fluorescence in water. These multicolor nanoparticles showed low cytotoxicity and good photostability, which could be used for fluorescence imaging of living cells.

Crystal structure of (Z)-2-benzyl-idene-4-methyl-2H-benzo[b][1,4]thia-zin-3(4H)-one.

In the title compound, C16H13NOS, the 1,4-thia­zine ring displays a screw-boat conformation. The conformation about the ethene bond [1.344 (2) Å] is Z. The plane of the fused benzene ring makes a dihedral angle of 58.95 (9)° with the pendent phenyl ring, indicating a twisted conformation in the mol­ecule. In the crystal, mol­ecules are linked by pairs of C—H⋯O hydrogen bonds, forming inversion dimers.

A Simple Extraction Method for Determination of High Molecular Weight Polycyclic Aromatic Hydrocarbons in Sediments by Gas Chromatography–Mass Spectrometry

AbstractA simplified extraction method was developed for extracting high molecular weight polycyclic aromatic hydrocarbons (PAHs) from river sediments. The samples were extracted 3 times with 5 mL of solvent (toluene:methanol, 9 : 1, v/v) at 100 °C, 10 minutes for each extraction. After clean‐up and concentration, extracts were analyzed by gas chromatography coupled with mass spectrometer (GC‐MS). The extraction efficiency and accuracy was evaluated by the standard reference material (SRM‐1941b). Comparing to certified values, the average recoveries of high molecular weight PAHs with 3, 4, 5 and 6 fused benzene rings were 72.9∼113.2 % (R.S.D. 2.3∼6.3 %) except those of dibenz[a,h]anthracene (206.2±4.6 %). The average recoveries for PAHs spiked sediment samples were comparable with accelerated solvent extraction (ASE) and Soxhlet methods. The simple extraction method consumes less solvent, fewer amount of sample than those of conventional methods. The lowest quantitation limit of PAHs is 1.1 μg/kg.

Short Synthesis of [5]- and [7]Phenacenes with Silyl Groups at the Axis Positions.

[5]Phenacene with trimethylsilyl groups at the axis positions was synthesized by the ruthenium-catalyzed direct C-H arylation of a 1-formyl-7-phenanthrene-derived aldimine, followed by sequential Wittig olefination and bismuth-catalyzed cyclization of the resulting vinyl ethers. By using the same synthetic building blocks and sequential Wittig olefination and photocyclization, the number of fused benzene rings was readily increased to seven to afford 3,12-disilyl[7]phenacene. The introduction of silyl groups endowed the [n]phenacene frameworks with good solubility, as well as enabling further functionalization. The electronic structure of these new [n]phenacenes was determined by photophysical measurements and by density functional theory calculations, which clearly implied effective conjugation throughout the entire π framework.

Crystal structure of bis-[(phenyl-methanamine-κN)(phthalocyaninato-κ(4) N)zinc] phenyl-methan-amine tris-olvate.

The asymmetric unit of the title compound, 2[Zn(C32H16N8)(C7H9N)]·3C7H9N, comprises two independent complex mol-ecules and three benzyl-amine solvent mol-ecules. Each complex mol-ecule features a penta-coordinated Zn(2+) ion within a square-pyramidal geometry, whereby the N5 donor set is defined by four atoms of the phthalocyaninate dianion (PC) and an N-bound benzyl-amine mol-ecule; it is the relative orientations of the latter that differentiate between the independent complex mol-ecules. The uncoordinated benzyl-amine mol-ecules display different conformations in the structure, with syn-Car-Car-Cm-N (ar = aromatic, m = methyl-ene) torsion angles spanning the range -28.7 (10) to 35.1 (14)°. In the crystal, N-H⋯N and N-H⋯π inter-actions lead to supra-molecular layers in the ab plane. The layers have a zigzag topology, have the coordinating and non-coordinating benzyl-amine mol-ecules directed to the inside, and present the essentially flat PC resides to the outside. This arrangement enables adjacent layers to associate via π-π inter-actions [inter-centroid distance between pyrrolyl and fused-benzene rings = 3.593 (2) Å] so that a three-dimensional architecture is formed.

Effects of Temperature, Substrate Concentration and pH on the Polycyclic Aromatic Hydrocarbon Pyrene Biodegradation by Arthrobacter sp. NJ5 Strain

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the environment and may persist for extended periods of time. PAHs are one of the most important classes of persistent organic contaminants. High molecular weight (HMW) PAHs (compounds containing four or more fused benzene rings) are generally recalcitrant to microbial attack. Until recently, only a few genera of bacteria have been isolated with the ability to utilize four-ring PAHs as sole carbon and energy sources. Because of the toxic, mutagenic, and carcinogenic characteristics of some, PAHs have been studied extensively by many scientists around the word. This paper presents research results, where 10 microbial strains belonging to genus Arthrobacter sp. and obtained from culture collection of JSC "Biocentras"were tested for the best biodegradation of HMW PAH pyrene. Pyrene degradation experiments were conducted in liquid mineral medium. Pyrene concentration was 0. 2 mg/mL at the beginning of degradation experiments. After 72 h incubation with ten Arthrobacter sp. strains, gas chromatography analysis revealed that highest pyrene degradation (19%) was reached by Arthrobacter sp. NJ5 strain. The effect of medium pH, pyrene concentration and temperature on the intensity of the degradation by the most active strain Arthrobacter NJ5 was investigated.

Crystal structure of methyl 7-phenyl-6a,7,7a,8,9,10-hexa-hydro-6H,11aH-thio-chromeno[3,4-b]pyrrolizine-6a--carbox-ylate.

In the title compound, C22H23NO2S, the inner pyrrolidine ring (A) adopts an envelope conformation with the methine C atom opposite the fused C—N bond as the flap. The thio­pyran ring (C) has a half-chair conformation and its mean plane is inclined to the fused benzene ring by 1.74 (11)°, and by 60.52 (11)° to the mean plane of pyrrolidine ring A. In the outer pyrrolidine ring (B), the C atom opposite the fused C—N bond is disordered [site-occupancy ratio = 0.427 (13):0.573 (13)] and both rings have envelope conformations, with the disordered C atom as the flap. The planes of the phenyl ring and the benzene ring of the thio­chromane unit are inclined to one another by 65.52 (14)°. In the crystal, mol­ecules are linked by a pair of C—H⋯O hydrogen bonds forming inversion dimers.

Crystal structure of methyl 3-(3-fluoro-phen-yl)-1-methyl-1,3a,4,9b-tetra-hydro-3H-thio-chromeno[4,3-c]isoxazole-3a-carboxyl-ate.

In the title compound, C19H18FNO3S, the five-membered oxazolidine ring adopts an envelope conformation with the methine C atom of the fused bond as the flap. Its mean plane is oriented at a dihedral angle of 50.38 (1)° with respect to the fluoro­phenyl ring. The six-membered thio­pyran ring has a half-chair conformation and its mean plane is almost coplanar with the fused benzene ring, making a dihedral angle of 4.94 (10)°. The two aromatic rings are inclined to one another by 85.96 (11)°, and the mean planes of the oxazolidine and thio­pyran rings are inclined to one another by 57.64 (12)°. In the crystal, mol­ecules are linked by C—H⋯π inter­actions, forming a three-dimensional structure.

Crystal structure of diethyl 2-[(2-sulfan-yl-quinolin-3-yl)methyl-idene]malonate.

In the title compound, C17H17N O4S, the quinoline ring system is nearly planar, with a maximum deviation of 0.0496 (16) Å. A weak intra­molecular C—H⋯O inter­action is observed. In the crystal, C—H⋯O, S—H⋯N and π–π stacking inter­actions between the fused benzene ring of quinoline and the pyridine moieties [shortest centroid–centroid distance = 3.6754 (11) Å] are observed. Inversion-related weak C—H⋯O inter­molecular inter­actions diagonally along [010], with R 2 2(10) ring motifs, and S—H⋯N inter­molecular inter­actions diagonally along [100], with R 2 2(8) ring motifs, are present, forming a three-dimensional network structure. No classical hydrogen bonds are observed.

Effect of pyrolysis temperature on char structure and chemical speciation of alkali and alkaline earth metallic species in biochar

To investigate the effect of pyrolysis temperature on char structure and chemical speciation of alkali and alkaline earth metallic (AAEM) species in biochar, experiments were carried out in an entrained flow reactor with nitrogen to reduce volatile–char interactions. Pyrolysis was conducted at temperatures ranging from 500°C to 900°C. Raman, Fourier transform infrared and X-ray photoelectron spectroscopies were used to identify the char structure and functional groups. The assessment of the chemical speciation of AAEM species in the biochar was carried out by chemical fractionation analysis and inductively coupled plasma mass spectrometry. Pyrolysis between 500 and 900°C results in ring condensation, which produces large aromatic ring systems containing six or more fused benzene rings. In addition, C–O and C–C linkages form through thermal polycondensation and cyclization to produce stable aromatic rings, which shows CC stretching bands in the FTIR. Conjugated aromatic carbonyl/carboxyl CO groups disappear at temperatures higher than 700°C, and the relative concentration of carbonyl oxygen from quinines increases gradually with increasing temperature. More than 50% of K and Na in the sawdust and chars prepared at 500–900°C exists as ions, while most of the Ca (65%) and Mg (60%) are bound in organic compounds. The release of K and Na occurs mainly in the form of inorganic salts and hydrated ions, while volatilization is the main release mechanism for Ca and Mg in the organic compounds.

Crystal structure of (6-bromo-2-oxo-2H-chromen-4-yl)methyl morpholine-4-carbodi-thio-ate.

In the title compound, C15H14BrNO3S2, the 2H-chromene ring system is nearly planar, with a maximum deviation of 0.034 (2) Å, and the morpholine ring adopts a chair conformation. The dihedral angle between best plane through the 2H-chromene ring system and the morpholine ring is 86.32 (9)°. Intra­molecular C—H⋯S hydrogen bonds are observed. In the crystal, inversion-related C—H⋯S and C—H⋯O inter­actions generate R 2 2(10) and R 2 2(8) rings patterns, respectively. In addition, the crystal packing features π–π inter­actions between fused benzene rings [centroid–centroid distance = 3.7558 (12) Å].

ChemInform Abstract: Unconventional, Chemically Stable, and Soluble Two‐Dimensional Angular Polycyclic Aromatic Hydrocarbons: From Molecular Design to Device Applications

AbstractReview: 51 refs.

First-principles investigation on the electronic efficiency and binding energy of the contacts formed by graphene and poly-aromatic hydrocarbon anchoring groups.

The electronic efficiency and binding energy of contacts formed between graphene electrodes and poly-aromatic hydrocarbon (PAH) anchoring groups have been investigated by the non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that PAH molecules always bind in the interior and at the edge of graphene in the AB stacking manner, and that the binding energy increases following the increase of the number of carbon and hydrogen atoms constituting the PAH molecule. When we move to analyzing the electronic transport properties of molecular junctions with a six-carbon alkyne chain as the central molecule, the electronic efficiency of the graphene-PAH contacts is found to depend on the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the corresponding PAH anchoring group, rather than its size. To be specific, the smaller is the HOMO-LUMO gap of the PAH anchoring group, the higher is the electronic efficiency of the graphene-PAH contact. Although the HOMO-LUMO gap of a PAH molecule depends on its specific configuration, PAH molecules with similar atomic structures show a decreasing trend for their HOMO-LUMO gap as the number of fused benzene rings increases. Therefore, graphene-conjugated molecule-graphene junctions with high-binding and high-conducting graphene-PAH contacts can be realized by choosing appropriate PAH anchor groups with a large area and a small HOMO-LUMO gap.

Crystal structure of (7-chloro-2-oxo-2H-chromen-4-yl)methyl N,N-di-methyl-carbamodi-thio-ate.

In the title compound, C13H12Cl N O2S2, the 2H-chromene ring system is almost planar, with a maximum deviation of 0.005 (2) Å. The packing features C—H⋯S hydrogen bonds and π–π inter­actions between fused benzene rings of chromene [shortest centroid–centroid distances = 3.6553 (13) and 3.5551 (13) Å].

Explorations of the solubilizing effectiveness of CH3OCH2CH2O substituents in the photocyclizations of some 1,2-diarylethylenes to [n]phenacenes

We have previously published many photocyclizations of 1,2-diarylethylenes to produce zig-zag aromatic ring systems with n=5, 7, and 11 fused benzene rings. We invented the name [n]phenacenes for these compounds. To increase their solubilities we attached either various alkyl or phenyl substituents. We present here our recent explorations of the effectiveness of CH3OCH2CH2O substituents as solubilizing groups in three examples of diarylethylene photocyclizations that produced one [5]phenacene and two [7]phenacene systems.

English

The potential of Pleurotus pulmonarius and Pleurotus ostreatus on the degradation of PAHs in spent and fresh cutting fluids (SCF and FCF) contaminated soils was investigated. Different weights of soil samples were contaminated with varying composition (10, 20 or 30%) of spent and fresh cutting fluids separately then inoculated each sample with P. pulmonarius and P. ostreatus separately and incubated at 28 ± 2°C for two months. The samples were analyzed in triplicates for 16 priority polycyclic aromatic hydrocarbons (PAHs) by gas chromatography after extracting with hexane and dichloromethane (3:1). The initial PAHs in the cutting fluids were mainly composed of 2 to 6 fused benzene rings. Significant reductions in PAHs concentrations for SCF and FCF were observed after two months of incubation. The percentage total PAHs remaining in FCF soil ranged from 71.7 to 73.6% when inoculated with P. pulmonarius and 0.93 to 31.0% when inoculated with P. ostreatus. Similarly, the percentage total PAHs remaining in SCF soil ranged from 42.6 to 72.6% when inoculated with P. pulmonarius and 54.9 to 62.2% when inoculated with P. ostreatus. Overall range of PAHs degradation by P. pulmonarius inoculated on FCF contaminated soil was 17.3 to 27.3%, while for P. ostreatus inoculated soil was 69.0 to 99.07% at different contamination levels. In contrast, overall PAHs degradation for P. pulmonarius and P. ostreatus inoculated on SCF ranged from 27.4 to 57.4% and from 37.8 to 45.2%, respectively. Thus, P. ostreatus is found more effective as a biodegradation agent for PAHs in contaminated soils when compared with P. pulmonarius.   Key words: Biodegradation, polycyclic aromatic hydrocarbons (PAHs), cutting fluids, Pleurotus ostreatus, Pleurotus pulmonarius.

CHARACTERIZING THE INFRARED SPECTRA OF SMALL, NEUTRAL, FULLY DEHYDROGENATED POLYCYCLIC AROMATIC HYDROCARBONS

We present the results of a computational study to investigate the infrared spectroscopic properties of a large number of polycyclic aromatic hydrocarbon (PAH) molecules and their fully dehydrogenated counterparts. We constructed a database of fully optimized geometries for PAHs that is complete for eight or fewer fused benzene rings, thus containing 1550 PAHs and 805 fully dehydrogenated aromatics. A large fraction of the species in our database have clearly non-planar or curved geometries. For each species, we determined the frequencies and intensities of their normal modes using density functional theory calculations. Whereas most PAH spectra are fairly similar, the spectra of fully dehydrogenated aromatics are much more diverse. Nevertheless, these fully dehydrogenated species show characteristic emission features at 5.2$\mu$m, 5.5$\mu$m and 10.6$\mu$m; at longer wavelengths, there is a forest of emission features in the 16--30$\mu$m range that appears as a structured continuum, but with a clear peak centered around 19$\mu$m. We searched for these features in Spitzer-IRS spectra of various positions in the reflection nebula NGC 7023. We find a weak emission feature at 10.68$\mu$m in all positions except that closest to the central star. We also find evidence for a weak 19$\mu$m feature at all positions that is not likely due to C$_{60}$. We interpret these features as tentative evidence for the presence of a small population of fully dehydrogenated PAHs, and discuss our results in the framework of PAH photolysis and the formation of fullerenes.

Evaluation of Stretching Properties of [7]Thiaheterohelicene Framework Called “Molecular Spring” Using AFM Force Measurements and Electrostatic State Calculations

Abstract The stretching properties of a [7]thiaheterohelicene framework, what we call molecular spring, have not been investigated so far, despite a variety of [7]thiaheterohelicene derivatives having very interesting characteristics due to both the rigidity arising from fused benzene rings and the flexibility like a spring originating from helical structure. In this study, a novel [7]thiaheterohelicene derivative, which has a disulfide moiety for bonding to a gold-coated substrate and a carboxy group for reacting with an amino-modified probe tip at each of its end groups, was synthesized in order to elucidate the elasticity of the [7]thiaheterohelicene framework by atomic force microscopy (AFM). The AFM force measurements were carried out using two carboxy-terminated disulfide derivatives with or without a [7]thiaheterohelicene moiety, and the deviation between two kinds of force–extension curves was related to the stretching originating from the [7]thiaheterohelicene framework here. Furthermore, its elasticity was compared to that of biphenyl, which is generally known as a rigid framework, using electrostatic state calculations.

Mechanical tuning of conductance and thermopower in helicene molecular junctions.

Helicenes are inherently chiral polyaromatic molecules composed of all-ortho fused benzene rings possessing a spring-like structure. Here, using a combination of density functional theory and tight-binding calculations, it is demonstrated that controlling the length of the helicene molecule by mechanically stretching or compressing the molecular junction can dramatically change the electronic properties of the helicene, leading to a tunable switching behavior of the conductance and thermopower of the junction with on/off ratios of several orders of magnitude. Furthermore, control over the helicene length and number of rings is shown to lead to more than an order of magnitude increase in the thermopower and thermoelectric figure-of-merit over typical molecular junctions, presenting new possibilities of making efficient thermoelectric molecular devices. The physical origin of the strong dependence of the transport properties of the junction is investigated, and found to be related to a shift in the position of the molecular orbitals.

Optical limiting and singlet oxygen generation properties of phosphorus triazatetrabenzcorroles

Novel phosphorus triazatetrabenzcorrole (TBC) tetrasubstituted at the α- and β-positions of the peripheral fused benzene rings with t-butylphenoxy substituents have been prepared and characterized. The effect of the substituents on the electronic structures and optical properties is investigated with TD-DFT calculations and MCD spectroscopy. The optical limiting properties have been investigated to examine whether the lower symmetry that results from the direct pyrrole–pyrrole bond and hence the permanent dipole moment that is introduced result in higher safety thresholds, relative to the values that have been reported for phthalocyanines. The suitability of the compounds for singlet oxygen applications has also been examined.