Fused Benzene Rings Research Articles

Involvement of the ligninolytic system of white-rot and litter-decomposing fungi in the degradation of polycyclic aromatic hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs) are natural and anthropogenic aromatic hydrocarbons with two or more fused benzene rings. Because of their ubiquitous occurrence, recalcitrance, bioaccumulation potential and carcinogenic activity, PAHs are a significant environmental concern. Ligninolytic fungi, such as Phanerochaete chrysosporium, Bjerkandera adusta, and Pleurotus ostreatus, have the capacity of PAH degradation. The enzymes involved in the degradation of PAHs are ligninolytic and include lignin peroxidase, versatile peroxidase, Mn-peroxidase, and laccase. This paper summarizes the data available on PAH degradation by fungi belonging to different ecophysiological groups (white-rot and litter-decomposing fungi) under submerged cultivation and during mycoremediation of PAH-contaminated soils. The role of the ligninolytic enzymes of these fungi in PAH degradation is discussed.

Fused Arene Ring Construction Around Pyrrole To Form 4,7‐Disubstitued Indole

AbstractA method for synthesizing 4,7‐diarylindoles and 4,7‐di(thien‐2‐yl)indole by applying a strategy where the fused benzene ring was built on an existing pyrrole in an acid‐catalyzed rearrangement of 1,4‐diaryl‐1,4‐di(pyrrol‐2‐yl)but‐2‐yne and 1,4‐di(pyrrol‐2‐yl)‐1,4‐di(thien‐2‐yl)but‐2‐yne, respectively, is presented. In the presence of TFA (30 equiv.), 4,7‐diarylindoles undergo thermodynamically equilibrated dimerization at 240 K as determined by 1H NMR spectroscopy and substantiated by DFT calculations.

S-wave superconductivity in barium-doped phenanthrene as revealed by specific-heat measurements

We report specific-heat studies on high-quality Ba-doped phenanthrene, one of the organic superconductors with fused benzene rings, with 100$%$ shielding fraction. The specific-heat data indicate that Ba-doped phenanthrene is a single-gap $s$-wave superconductor with moderate coupling, and this sets constraints on theoretical models for the understanding of superconductivity in these hydrocarbon superconductors.

1-Ethyl-4-[1-(1-phenylethylidene)hydrazin-2-ylidene]-3,4-dihydro-1H-2λ6,1-benzothiazine-2,2-dione

In the title compound, C18H19N3O2S, the thia­zine ring adopts an envelope conformation, with the S atom displaced by 0.732 (1) Å from the other atoms of the ring. The phenyl ring is oriented at a dihedral angle of 79.33 (7)° with respect to the fused benzene ring. The conformations about the two double bonds in the R 2C=N—N=C(CH3)Ar grouping are Z and E, respectively. In the crystal, inversion dimers linked by pairs of C—H⋯O inter­actions generate R 2 2(8) and R 2 2(12) loops, as parts of infinite chains along the a-axis direction.

Aromaticity of five- and six-membered heterocycles present in crude oils – An electronic description for hydrotreatment process

The present work is focused on attempt to understand the importance of aromaticity in the elimination of N, O and S atoms from five-membered heterocycles and catalyst poisoning by basic nitrogen six-membered heterocyclic compounds in the hydrotreatment (HDT) process. Pyrrole, furan, thiophene and pyridine, and their fused benzene ring derivatives have been studied by means of density functional theory (DFT). Proton affinities (PAs) were calculated for all these compounds, geometrical modifications were observed during protonation. Five-membered aromatic compounds break planarity due to proton interaction of the heteroatom, while pyridine-type compounds do not. Aromatic stabilization energy (ASE) was calculated by homodesmotic chemical reactions for all heterocyclic compounds. The energetic trends for protonated and unprotonated compounds confirm the less reactivity of dibenzo-compounds in the HDT process and catalyst’s poisoning by pyridine derivatives present in crude oils.

Superconductivity above 30 K in alkali-metal-doped hydrocarbon

The recent discovery of superconductivity with a transition temperature (Tc) at 18 K in Kxpicene has extended the possibility of high-Tc superconductors in organic materials. Previous experience based on similar hydrocarbons, like alkali-metal doped phenanthrene, suggested that even higher transition temperatures might be achieved in alkali-metals or alkali-earth-metals doped such polycyclic-aromatic-hydrocarbons (PAHs), a large family of molecules composed of fused benzene rings. Here we report the discovery of high-Tc superconductivity at 33 K in K-doped 1,2:8,9-dibenzopentacene (C30H18). To our best knowledge, it is higher than any Tc reported previously for an organic superconductor under ambient pressure. This finding provides an indication that superconductivity at much higher temperature may be possible in such PAHs system and is worthy of further exploration.

N-Benzylisatin

In the title compound, C15H11NO2, two C—H⋯O hydrogen bonds are observed in the crystal structure, as well as π–π stacking with a centroid–centroid distance of 3.623 (2) Å. The planarity of the two ring systems is illustrated by very small deviations of all the atoms from these planes [largest deviations = 0.003 (3) and 0.010 (3) Å for the phenyl and fused-benzene rings, respectively]. The dihedral angle between these two planes is 77.65 (9)°.

Reactivity of acenes: mechanisms and dependence on acene length

Acenes are polycyclic aromatic hydrocarbons consisting of linearly fused benzene rings. These compounds are currently the subject of great interest from both fundamental and applied perspectives, particularly for use in organic electronics. This review highlights the computational studies carried out to understand acene reactivity, their reaction mechanisms, and the relationship of the latter to acene length. Generally, as acene length increases, the reactivity of acenes increases, and a greater tendency towards a biradical mechanism is observed. For example, an interesting change in mechanism (from concerted to biradical) is observed for the reaction of acenes (benzene through pentacene) with molecular oxygen. A computational study of the addition of HCl (which behaves as an electrophile) and water (which behaves mostly as a nucleophile) to acenes revealed that acene reactivity increases along the series up to hexacene and remains constant from hexacene and above because of the biradical character of the ground state of higher acenes. Although the exothermicity of the addition of water and HCl to acene is similar, the activation barrier for the addition of water is significantly higher than that for HCl. There is a substantial substituent effect on the energy barriers for electrophilic and nucleophilic reactions. Phenyl substitution at the most reactive meso‐carbon atoms of the central ring of acene blocks dimerization through this ring but does not efficiently prevent dimerization through other rings. With respect to the self‐reactivity (such as dimerization, etc.) of acenes, a computational study showed that the preferred pathways are the formation of acene dimers via a central benzene ring and the formation of acene‐based polymers. Interestingly, longer acenes are predicted to self‐react to form polymers, rather than acene dimers, as the thermodynamically preferred product. These findings invite experimentalists to reinvestigate the dimerization of long unsubstituted acenes. Given that computational studies directly relate to the gas phase reactivity of acenes, whereas long acenes find application in organic semiconductor devices as solids, the next research challenge is to obtain an understanding of the solid state reactivity of long acenes. Copyright © 2012 John Wiley & Sons, Ltd.

Terpyridine-fused polyaromatic hydrocarbons generated via cyclodehydrogenation and used as ligands in Ru(ii) complexes

A series of novel fused 4'-substituted 2,2' : 6',2''-terpyridine ligands and their ruthenium(II) complexes were prepared. The unusual 4'-substituents comprised 2,3,4,5-pentaphenylbenzene and its tert-butyl derivative (1 and 2) and the products from oxidative cyclodehydrogenation, i.e. polyaromatic fragments consisting of ten or thirteen fused benzene rings (3 and 4). The syntheses of all the ligands are discussed in terms of the demands and limitations of the Scholl reaction. The optical properties of the ligands, along with the single-crystal X-ray structures of 1 and 2, are presented. The latter show that the pentaphenylbenzene and terpyridine appendages of 1 and 2 are perpendicular in the solid state. Despite the inclusion of the large organic chromophore the absorption and emission properties of the Ru(II) bis-terpy complexes (of ligands 1, 2 and 3) were found to be comparable to those of [Ru(terpy)(2)](2+). They are non-emissive at room temperature but emit at 77 K with excited state lifetimes of 11-12 μs.

π‐Electron currents in larger fully aromatic benzenoids

AbstractRecently, we have reported on calculation of π‐electron ring currents in several smaller fully benzenoid hydrocarbons having up to eight fused benzene rings and five Clar π‐aromatic sextets. In contrast to early HMO ring current calculations and more recent ab initio calculations of π‐electron density, our current calculations are based on a graph theoretical model in which contributions to ring currents comes from currents associated with individual conjugated circuits. In this contribution, we consider several larger fully benzenoid hydrocarbons having from 9 to 13 fused rings and from six or seven π‐aromatic sextets. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

5-Acetyl-3-hydroxy-4-phenyl-4,5-dihydro-1H-1,5-benzodiazepin-2(3H)-one

In the title compound, C17H16N2O3, the seven-membered diazepine ring adopts a boat conformation with the hy­droxy-substituted C atom at the prow and fused benzene ring C atoms at the stern. The phenyl substituent occupies an equatorial position. The amino group of the ring system is a hydrogen-bond donor to the oxo O atom of an inversion-related mol­ecule, and the hy­droxy group is a hydrogen-bond donor to the acetyl O atom of another inversion-related mol­ecule. The two hydrogen bonds generate a ribbon motif parallel to [10] in the crystal structure.

16]Cloverphene: a Clover‐Shaped cata‐Condensed Nanographene with Sixteen Fused Benzene Rings

Living in clover: Sequential [4+2] and [2+2+2] aryne cycloadditions allow the isolation of cloverlike and archlike nanographenes (see picture). This approach led to the synthesis of the largest cata-condensed aromatic hydrocarbon that has been obtained to date, a system formed by 16 fused benzene rings (22 benzene rings in total) and 102 sp2 carbon atoms.

16]Cloverphene: a Clover‐Shaped cata‐Condensed Nanographene with Sixteen Fused Benzene Rings

16]Cloverphene: a Clover‐Shaped <i>cata</i>‐Condensed Nanographene with Sixteen Fused Benzene Rings

Design of Covalent Organic Frameworks for Methane Storage

We designed 14 new covalent organic frameworks (COFs), which are expected to adsorb large amounts of methane (CH(4)) at 298 K and up to 300 bar. We have calculated their delivery uptake using grand canonical Monte Carlo (GCMC) simulations. We also report their thermodynamic stability based on 7.5 ns molecular dynamics simulations. Two new frameworks, COF-103-Eth-trans and COF-102-Ant, are found to exceed the DOE target of 180 v(STP)/v at 35 bar for methane storage. Their performance is comparable to the best previously reported materials: PCN-14 and Ni-MOF-74. Our results indicate that using thin vinyl bridging groups aid performance by minimizing the interaction methane-COF at low pressure. This is a new feature that can be used to enhance loading in addition to the common practice of adding extra fused benzene rings. Most importantly, this report shows that pure nonbonding interactions, van der Waals (vdW) and electrostatic forces in light elements (C, O, B, H, and Si), can rival the enhancement in uptake obtained for microporous materials derived from early transition metals.

7′-Phenyl-5′,6′,7′,7a′-tetrahydrodipiro[indan-2,5′-pyrrolo[1,2-c][1,3]thiazole-6′,2′′-indan]-1,3,1′′-trione

The asymmetric unit of the title compound, C28H21NO3S, contains two mol­ecules with similar geometries. The thia­zolidine rings adopt half-chair conformations while the pyrrolidine and the diketo-substituted five-membered carbocyclic rings are in envelope conformations with the spiro C atoms at the flaps. In one mol­ecule, the phenyl ring forms dihedral angles of 57.76 (12) and 71.79 (12)° with the fused benzene rings and the fused benzene rings form a dihedral angle of 57.75 (13)°. The corresponding dihedral angles in the other mol­ecule are 60.04 (12), 72.93 (12) and 54.51 (13)°. The mol­ecular structure is stabilized by intra­molecular C—H⋯O hydrogen bonds, which generate S(6) ring motifs. In the crystal, mol­ecules are linked via C—H⋯O and C—H⋯N hydrogen bonds into layers lying parallel to the ab plane.

ChemInform Abstract: The Chemistry of Pyrido[1,2‐a]azepines and Their Hydro Derivatives

AbstractReview: ca. 200 refs.

(1R,2S)-Methyl 1-(4-chlorophenyl)-3-oxo-1,2,3,4-tetrahydrocyclopenta[b]indole-2-carboxylate 0.2-hydrate

The title compound, C19H14ClNO3·0.2H2O, crystallizes with five mol­ecules and a disordered water mol­ecule in the asymmetric unit. Four of the five mol­ecules form hydrogen-bonded dimers via N—H⋯O hydrogen bonds towards another symmetry-independent mol­ecule, whereas the fifth mol­ecule forms a hydrogen-bonded dimer with its symmetry equivalent, also via N—H⋯O hydrogen bonds. The dihedral angle between the planes of the fused benzene ring and the five-membered ring to which it is attached is 79.45 (13), 49.00 (15), 72.49 (16), 81.91 (18) and 76.38 (16)° for the five mol­ecules in the asymmetric unit.

Inhibitive Effect ofArgemone mexicanaPlant Extract on Acid Corrosion of Mild Steel

The effect of plant extract of Papaveraceae family Argemone mexicana is studied for use as a low cost and efficient corrosion inhibitor for mild steel in acidic environment. This plant extract is selected for the study of corrosion inhibition in view of its rich source of organic inhibiting molecules as proteins, amino acids, tannins, phenolic compounds, saponins, and flavonoids and nonalkaloids organic compounds such as fused benzene rings, hetero N atom rings, −OCH3, and −OH groups. A simple extraction method is adopted to obtain water-based plant extract. Argemone mexicana extract is for the first time used as an efficient inhibitor for mild steel in 1 M HCl. Weight loss and electrochemical methods are used to study the corrosion. Nearly 80% corrosion inhibition is observed at around 200 mg L–1 inhibitor concentration and maximum (92.5%) for 500 mg L–1 extract concentration in 1 M HCl. Inhibition mechanism is studied using UV–vis, electrochemical, and surface imaging techniques.

Conjugated di- and trinuclear phthalocyanines and their analogs

Extended π-electron delocalization is the most important property of phthalocyanines and structurally related systems. The position of the longest wavelength absorption (Q-band) is influenced by the kind of substituents and by additional fused benzene rings at the ligand. Very large wavelength shifts are obtained with planar annulated di- and trinuclear phthalocyanine analogs sharing a common benzene ring which are the main point of this review. In addition, condensed di- and trinuclear phthalocyanines, and di- and trinuclear phthalocyanines linked via one or two carbon atoms of the macrocycles are discussed for comparison.

9,9-Dimethyl-9,10-dihydroanthracene

In the title compound, C16H16, the central benzene ring adopts a boat conformation, with a dihedral angle of 34.7 (9)° between the mean planes of the two fused benzene rings. The two methyl groups at the apex of the central benzene ring are in axial and equatorial conformations. The crystal packing is stabilized by weak C—H⋯π inter­molecular inter­actions.