Substituted Benzene Rings Research Articles

1-(2,4-Di-nitro-phen-yl)-2-[(E)-(3,4,5-tri-meth-oxy-benzyl-idene)]hydrazine.

Mol­ecules of the title compound, C16H16N4O7, are not planar with a dihedral angle of 5.50 (11)° between the substituted benzene rings. The two meta-meth­oxy groups of the 3,4,5-tri­meth­oxy­benzene moiety lie in the plane of the attached ring [Cmeth­yl–O–C–C torsion angles −0.1 (4)° and −3.7 (3)°] while the para-meth­oxy substituent lies out of the plane [Cmeth­yl—O—C—C, −86.0 (3)°]. An intra­molecular N—H⋯O hydrogen bond involving the 2-nitro substituent generates an S(6) ring motif. In the crystal structure, mol­ecules are linked by weak C—H⋯O inter­actions into screw chains, that are arranged into a sheet parallel to the bc plane. These sheets are connected by π–π stacking inter­actions between the nitro and meth­oxy substituted aromatic rings with a centroid–centroid separation of 3.9420 (13) Å. C—H⋯π contacts further stabilize the two-dimensional network.

Synthesis of New Thienylene Pyrrole Monomers and Their Electropolymerizations

In this study, four new 2,5-dithienylpyrroles (SNS) 1-(3-fluoro-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-FPTP), 1-(3-chloro-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-ClPTP),1-(3-bromo-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (m-BrPTP) and 1-(4-bromo-phenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole (p-BrPTP) containing meta and para substituted benzene ring at the nitrogen atom were synthesized via Paal-Knorr condensation of 1,4-di(2-thienyl)-1,4-butanedione with corresponding halo-substituted anilines. The monomers were polymerized via potential cycling in LiClO4-acetonitrile (ACN) electrolytic solution. The replacement effect of halogen atoms as a substituent from para- to meta-positions and different halogen units (F, Cl, Br) at only meta-/para-positions in the structure on the electrochemical and optical properties of synthesized monomers/polymers were investigated. Computational investigations (M06/TZVP) were also performed on the monomer structures to support the electrochemical behavior of the monomers and to get more insight about the conformation of the structures. Furthermore, the synthesized polymer films exhibited reversible redox behavior accompanied with a reversible electrochromic behavior. It was also observed that the optical contrast value (ΔT%) for polymers was significantly improved when compared with their analogs in the literature.

(E)-1-(2,4-Dinitrophenyl)-2-(3-ethoxy-4-hydroxybenzylidene)hydrazine

The mol­ecule of the title hydrazine derivative, C15H14N4O6, is essentially planar, the dihedral angle between the substituted benzene rings being 2.25 (9)°. The eth­oxy and hy­droxy groups are almost coplanar with their bound benzene ring [r.m.s. deviation = 0.0153 (2) Å for the ten non-H atoms]. Intra­molecular N—H⋯O and O—H⋯Oeth­oxy hydrogen bonds generate S(6) and S(5) ring motifs, respectively. In the crystal, mol­ecules are linked by O—H⋯Onitro hydrogen bonds into chains propagating in [010]. Weak aromatic π–π inter­actions, with centroid–centroid distances of 3.8192 (19) and 4.0491 (19) Å, are also observed.

(E)-2-[(2,4,6-Trimethoxybenzylidene)amino]phenol

There are two independent mol­ecules in the asymmetric unit of the title compound, C16H17NO4, with similar conformations but some differences in their bond angles. Each mol­ecule adopts a trans configuration with respect to the methyl­idene C=N bond and is twisted with a dihedral angle between the two substituted benzene rings of 80.52 (7)° in one mol­ecule and 83.53 (7)° in the other. All meth­oxy groups are approximately coplanar with the attached benzene rings, with Cmeth­yl—O—C—C torsion angles ranging from −6.7 (2) to 5.07 (19)°. In the crystal, independent mol­ecules are linked together by O—H⋯N and O—H⋯O hydrogen bonds and a π–π inter­action [centroid–centroid distance of 3.6030 (9) Å], forming a dimer. The dimers are further linked by weak C—H⋯O inter­actions and another π–π inter­action [centroid–centroid distance of 3.9452 (9) Å] into layers lying parallel to the ab plane.

3-(4-Aminophenyl)-5-(4-methoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbothioamide

In the mol­ecule of title pyrazoline derivative, C17H18N4OS, the pyrazole ring adopts an envelope conformation with the flap atom, which bears the meth­oxy­phenyl substituent, displaced by 0.0750 (12) Å from the plane through the other ring atoms. The two substituted benzene rings make a dihedral angle of 70.59 (6)°. The meth­oxy group is twisted slightly with respect to the attached benzene ring [Cmeth­yl—O—C—C torsion angle = −8.84 (15)°]. An intra­molecular N—H⋯N hydrogen bond occurs. In the crystal, the pyrazoline mol­ecules are linked by N—H⋯O and N—H⋯S hydrogen bonds into zigzag layers parallel to the bc plane and stacked along the a axis by π–π inter­actions with centroid–centroid distances of 3.4690 (7) and 3.5792 (7) Å. C—H⋯π inter­actions are also present.

Variational RRKM theory calculation of thermal rate constant for carbon—hydrogen bond fission reaction of nitro benzene

The present work provides quantitative results for the rate of unimolecular carbon-hydrogen bond fission reaction of benzene and nitro benzene at elevated temperatures up to 2000 K. The potential energy surface for each C-H (in the ortho, meta, and para sites) bond fission reaction of nitro benzene was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C-H bond fission channel is barrier less reaction, we have used variational RRKM theory to predict rate constants. By means of calculated rate constant at the different temperatures, the activation energy and exponential factor were determined. The Arrhenius expression for C-H bond fission reaction of nitro benzene on the ortho, meta and para sites are k(T) = 2.1 × 1017exp(−56575.98/T), k(T) = 2.1 × 1017exp(−57587.45/T), and k(T) = 3.3 × 1016exp(−57594.79/T) respectively. The Arrhenius expression for C-H bond fission reaction of benzene is k(T) = 2 × 1018exp(−59343.48.18/T). The effect of NO2 group, location of hydrogen atoms on the substituted benzene ring, reaction degeneracy, benzene ring resonance and tunneling effect on the rate expression have been discussed.

Further Investigations into the Regioselectivity of 6,7-Indole Aryne Cyclo­additions with 2-Substituted Furans: Remarkable Contrasteric Preference Depends­ on Pyrrole and Benzene Ring Substitution

A series of related 6,7-dibromoindole compounds were prepared to study the effects of pyrrole and benzene ring substitution patterns on the regioselectivity of 6,7-indole aryne cycloadditions with 2-<i>tert</i>-butylfuran. The arynes were generated by our metal–halogen exchange/elimination protocol. The results of this investigation reveal that substitution at the 3-position on the indole ring in particular results in remarkable regiocontrol that favored the contrasteric products. Aromatic conjugation at this site significantly enhanced this effect. However, the presence of most 4- or 5-substituents generally resulted in markedly reduced selectivity. Exceptions in this latter series included the 4-ethyl and 4-iodo cases both of which also gave predominantly contrasteric products even in the absence of a beneficial C-3 substituent.

A study of slow pyrolysis of one low rank coal via pyrolysis–GC/MS

This paper describes the study of one low rank coal (LRC). To investigate its molecular structure, a LRC was characterized by proximate and ultimate analyses, XRD, FTIR, Raman spectroscopy, and pyrolysis–GC/MS (py–GC/MS). The light volatile fraction of LRC was characterized via py–GC/MS. LRC's aromatic ring structures consist of 59% amorphous structures, 22% of highly ordered structures with no less than 6 rings, 16% of aromatic structures characterized by aliphatic and/or ether substitutions and 3% of substituted benzene rings. XRD results show that the crystalline unit of LRC contains 1.44 aromatic carbon atoms per aliphatic carbon atom. Aromatic cluster structures within LRC are interconnected via ether- and covalent CC bonds. Hydroxyl, ether and carbonyl functionalities give LRC its polar character. The slow pyrolysis of LRC resulted in a light volatile GC/MS detected fraction consisting of 20% aromatic ring compounds, 45% of phenolics, 30% of aliphatic hydrocarbons and 5% O-compounds, of which the concentration, evolution and nature were dependent on the heating rates and end temperatures. Generally, slow pyrolysis of LRC at 700°C yielded the highest concentrations of unsaturated acyclic hydrocarbons, aromatics and phenolics.

4-[(E)-(4-Ethoxybenzylidene)amino]phenol

The mol­ecule of the title compound, C15H15NO2, adopts a trans conformation with respect to the methyl­idene C=N bond and is twisted with a dihedral angle of 26.31 (5)° between the two substituted benzene rings. The eth­oxy group is almost coplanar with the bound benzene ring with a C—O—C—C torsion angle of −179.08 (9)°. In the crystal, mol­ecules are linked by O—H⋯N hydrogen bonds and weak C—H⋯O inter­actions into chains propagating in the [011] and [01-1] directions. C—H⋯π inter­actions are also present.

Efficient and Accurate Theoretical Methods To Investigate Anion-π Interactions in Protein Model Structures

Anion-π interactions are attractive interactions between electron-poor aromatic rings and electron-rich negative ions or groups. Predicted by theoretical studies in the late 1990s, the first experimental evidence of anion-π interactions was provided by two independent studies in 2004. Since then, the role of these interactions in chemical and in biochemical systems has been investigated. In this work we report benchmark interaction energies, estimated from the extrapolated MP2 basis set limit with CCSD(T) correction, for several model complexes. These are then used to assess faster, more approximate methods including MP2 and its local approximation, along with various forms of Density Functional Theory (DFT). The most promising of these are then used to describe the geometries and interaction energies of a series of complexes between electron-poor substituted benzene rings and anions as well as examples of such interactions in models of proteins.

Star-Shaped D–A Small Molecules Based on Diketopyrrolopyrrole and Triphenylamine for Efficient Solution-Processed Organic Solar Cells

Three star-shaped D-A small molecules, (P-DPP)(3)TPA, (4-FP-DPP)(3)TPA, and (4-BuP-DPP)(3)TPA were designed and synthesized with triphenylamine (TPA) as the core, diketopyrrolopyrrole (DPP) as the arm, and unsubstituted or substituted benzene rings (phenyl, P; 4-fluoro-phenyl, 4-FP; 4-n-butyl-phenyl, 4-BuP) as the end-group. All the three small molecules show relatively narrow optical band gaps (1.68-1.72 eV) and low-lying highest occupied molecular orbital (HOMO) energy levels (-5.09∼-5.13 eV), implying that they are potentially good electron donors for organic solar cells (OSCs). Then, photovoltaic properties of the small molecules blended with [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) as electron acceptor were investigated. Among three small molecules, the OSC based on (P-DPP)(3)TPA:PCBM blend exhibits a best power conversion efficiency (PCE) of 2.98% with an open-circuit voltage (V(oc)) of 0.72 V, a short-circuit current density (J(sc)) of 7.94 mA/cm(2), and a fill factor (FF) of 52.2%, which may be ascribed to the highest hole mobility of (P-DPP)(3)TPA.

Synthesis, Spectroscopic Investigations, Quantum Chemical Studies (&amp;lt;i&amp;gt;Ab-initio&amp;lt;/i&amp;gt; &amp;amp; DFT) and Antimicrobial Activities of 3-(3-Chloro-4,5-dimethoxy-phenyl)-1-(4, 5-dimethoxy-2-methyl-Phenyl) prop-2-en-1-one

The chalcones (1,3-diaryl-2-propenones) and their derivatives are important intermediates in organic synthesis and have widespread applications in medicinal industry. The title choloro chalcone derivative, 3-(3-chloro-4,5-dimethoxyphenyl)-1-(4,5-dimethoxy-2-methyl phenyl) prop-2-en-1-one, has been synthesized. It is characterized by FTIR, 1H NMR, 13C NMR and single crystal X-ray diffraction. Title compound crystallizes in monoclinic space group C2/c with a = 23.540(11) ?, b = 9.738(4) ?, c = 17.305(7) ?, β = 106.37 (3)°, V = 3806(3) ?3 and Z = 8. The mean plane of the two substituted benzene rings are twisted by 66.29 (12)° with respect to each other. Ab-initio and density functional Theory (DFT) calculations have been carried out for the title molecule using RHF/6-311G and B3LYP/6-311G basis set respectively. The calculated results show that the predicted geometry can well reproduce structural parameters. In addition, frontier molecular orbitals and Mullikan charge distributions are carried out by using RHF and B3LYP methods. The calculated HOMO and LUMO energies show that charge transfer occurs in the molecule. Numbers of weak but significant interactions like C-H···O, C-H···π and π-π are involved in the stability of the structure. The weak π-π stacked interaction involves the centroids of the methyl phenyl rings with Cg-Cg separation distance of 3.857(2) ?. Synthesized compound has been screened for its antimicrobial activity against different panels of organisms.

Structure-Activity Relationships of 3,3′-Phenylmethylene-bis-4-hydroxycoumarins: Selective and Potent Inhibitors of Gram-Positive Bacteria

Dicoumarols and coumarin derivatives have shown a variety of pharmaceutical activities and have been found to be potent inhibitor for the NAD(P)H-dependent flavoproteins. In this report, dicoumarol and its derivatives containing the substituted benzene ring at the methylenebis position were synthesized and evaluated for their antibacterial activity against gram-positive bacteria: Staphylococcus aureus and Bacillus subtilis, and gram-negative bacteria: Escherichia coli and Klebsiella sp. The results showed that the synthesized dicoumarols affect cell growth but are selective against gram-positive over gram-negative bacterial cells. However, for most derivatives, the substitution of steric bulky benzene group on the methylenebis position appears to decrease in the efficacy of antibacterial effect. This finding is roughly described by the predicted poorer docked structure of the derivatives to a homology model of S. aureus flavoprotein. 3D-QSAR study highlighted structural features around the substituted benzene ring of dicoumarols as the antibacterial activity. CoMFA and CoMSIA contour maps support the idea that steric repulsion at the para position could diminish the antibacterial activity. The results of this study provide a better understanding of the molecular basis for the antibacterial activity of dicoumarols.

Cis-Dichloridobis(2-isocyanophenyl 4-methoxybenzoate)palladium(II) chloroform monosolvate

In the title compound, [PdCl2(C15H11NO3)2]·CHCl3, the PdII atom adopts a slightly distorted square-planar coordination geometry composed of two Cl atoms in cis positions and two C atoms from isocyano­phenyl ligands. The mol­ecular conformation is stabilized by π–π stacking inter­actions [shortest centroid–centroid distance = 3.600 (1) Å] between substituted benzene rings of different ligands. The crystal packing is characterized by C—H⋯O and C—H⋯Cl inter­actions involving the chloro­form solvent mol­ecules.

3-(2-Chloro-3-hydroxy-4-methoxyphenyl)-1-(4,5-dimethoxy-2-methylphenyl)prop-2-en-1-one

The title compound, C19H19ClO5, is a chloro derivative of a biologically significant chalcone family. The mean plane of the two substituted benzene rings are twisted by 55.33 (8)° with respect to each other. An intra­molecular C—H⋯Cl hydrogen bond generates an S(5) graph-set motif. In the crystal, a bifurcated O—H⋯(O,O) hydrogen bond leads to an R 1 2(5) graph-set motif and to the formation of zigzag chains propagating along the c-axis direction. A weak π–π inter­action involving the methyl­phenyl rings [centroid–centroid distance = 3.8185 (10) Å] and C—H⋯π inter­actions also occur.

Structure–activity relationship study of thiosemicarbazones on an African trypanosome: Trypanosoma brucei brucei

To explore the structure–activity relationships of thiosemicarbazones on African trypanosome: Trypanosoma brucei brucei, a series of thirty-five thiosemicarbazones (1–35) have been synthesized and characterized by their 1H NMR, 13C NMR, and FT-IR spectra. All compounds were tested for trypanocidal activity using the method “Lilit alamar blue”. The comparison of trypanocidal power of thiosemicarbazones was performed considering their structures. This study that was done using acetophenone thiosemicarbazone (1) as basic model, showed that: (a) the presence of lipophilic substituents in para position on benzene ring, (b) substitution of benzene ring and (c) substitution of hydrogen of thioamide function by a phenyl, strongly influence trypanocidal activity. The various modifications to basic structure (1) allowed the synthesis of 1-(4-chlorophenyl) ethylidene-4-phenyl-thiosemicarbazide (34). With a trypanocidal activity of 3.97 μM, this compound is the most active of the series.

Raman and IR spectroscopic studies of fenamates – Conformational differences in polymorphs of flufenamic acid, mefenamic acid and tolfenamic acid

Solid-state Raman and IR spectra of two polymorphic forms of each of three fenamates (flufenamic acid, mefenamic acid and tolfenamic acid) display subtle but highly reproducible differences. Many of these spectral differences can be ascribed to different conformations of these molecules, involving two of four possible orientations of one substituted benzene ring with respect to the other. Interpretation of the vibrational spectra in terms of conformational differences has been facilitated by DFT calculations at the B3LYP/cc-pVDZ level for each conformer. The calculated spectra are compared with the experimental spectra in order to identify the conformers present in two polymorphic forms in each case, and detailed band assignments are obtained from the DFT calculations.

Aromatic Cations from Oxidative Carbon–Hydrogen Bond Cleavage in Bimolecular Carbon–Carbon Bond Forming Reactions

Chromenes and isochromenes react quickly with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to form persistent aromatic oxocarbenium ions through oxidative carbon-hydrogen cleavage. This process is tolerant of electron-donating and electron-withdrawing groups on the benzene ring and additional substitution on the pyran ring. A variety of nucleophiles can be added to these cations to generate a diverse set of structures.

Synthesis and antitumor activity of novel quinazoline derivatives containing thiosemicarbazide moiety

Series of novel derivatives of quinazoline containing thiosemicarbazide moiety 5 and 9 have been synthesized and tested for their antitumor activities in vitro against a panel of five human cancer cell lines. Bioassay results indicated that most of the prepared compounds exhibited cytotoxicity against various cancer cells. From the structure–activity relationships it was found that unsubstituted quinazoline ring and benzene ring or halogen substituted benzene ring in quinazoline derivatives 5 and 9 would be the most favorable for their antitumor activity.

{4,4′,6,6′-Tetrabromo-2,2′-[2,2-dimethylpropane-1,3-diylbis(nitrilomethanylylidene)]diphenolato}nickel(II)

The asymmetric unit of the title compound, [Ni(C19H16Br4N2O2)], comprises half of a Schiff base complex. The geometry around the NiII atom, located on a twofold rotation axis, is distorted square-planar, which is supported by the N2O2 donor atoms of the coordinated ligand. The dihedral angle between the substituted benzene rings is 23.19 (17)°. In the crystal, a short inter­molecular Br⋯Br [3.6475 (7) Å] inter­action is present.