Benzene Moiety Research Articles

Tris(3,4‐dimethylenecyclobuteno)benzene Derivatives with Enhanced Carbon–Carbon Bond‐Length Alternation in Annelated Benzene

Computational analyses of the tris(3,4‐dimethylenecyclobuteno)benzene molecule indicate that the absence of the equivalent of a HOMO of an etheno group between the internal carbon atoms of the annelating butadieno groups is mainly responsible for the relatively weak cyclohexatriene‐like fixation in the central benzene ring. To increase the extent of C–C bond‐length alternation in the benzene moiety, two strategies of modification of the annelating groups are proposed to make the presence of the equivalent of a HOMO of an etheno group between the internal carbon atoms of the annelating butadieno groups. The first is to introduce a π‐electron‐donating heteroatom/group to form a five‐membered ring with the annelating butadieno groups (model I). The extent of bond‐length alternation could be tuned by the choice of the heteroatom/group in model I. The second is to coordinate with transition‐metal groups, such as the irontricarbonyl groups, for the annelating butadieno groups (model II). Computational results predict that molecules generated by using these two strategies could form strong cyclohexatriene‐like fixation of the double bonds in the central benzene ring.

Chiral benzo-fused Aza-BODIPYs with optical activity extending into the NIR range

Chiral benzo-fused aza-BODIPYs, namely N,N-difluoroboryl-[(dinaphtho[1,2-e:1′,2′-g]-1,4-dioxocine)-1-[N-(3-phenyl-2H-isoindole-1-yl)methylene]-3-phenyl-1H-isoindol-1-ylidene)amine] (1) and N,N-difluoroboryl-[(dinaphtho[1,2-e:1′,2′-g]-1,4-dioxocine)-1-[(dinaphtho[1,2-e:1′,2′-g]-1,4-dioxocine)-N-(3-phenyl-2H-isoindole-1-yl)methylene]-3-phenyl-1H-isoindol-1-ylidene)amine] (2), have been synthesized and spectroscopically characterized. Fusion of benzene moieties onto the BODIPY periphery in combination with the introduction of peripheral chiral binaphthyl substituents renders the extension of optical activity of resulting chiral benzo-fused aza-BODIPYs into the near-IR (NIR) range, representing the first chiral BODIPYs with NIR optically activity. For comparative study, N,N-difluoroboryl-[N-(3-phenyl-2H-isoindol-1-yl)-N-(3-phenyl-1H-isoindol-1-ylidene)amine] (0) was also prepared and characterized in a similar manner.

Electron density analysis of bent aromatic molecules: intramolecular interactions in small paracyclophanes

The electron distribution of molecules with distorted aromatic rings was analyzed using theoretical methods. The molecular geometries of Dewar benzene, the series of [n]paracyclophanes (n = 2, \(\ldots\), 6), and [1.1] and [2.2]paracyclophane were optimized at the QCISD/6-31++G(d,p) approximation. The partition of three-dimensional space provided by the quantum theory of atoms in molecules was applied using the electron densities obtained at this highly correlated level of theory. The analysis shows that Dewar benzene and [2]paracyclophane belong in a separate family. In the other cases, the distortion of the benzene moiety provokes a charge transfer to the phenylene group and induces a moderate single bond–double bond alternation that yields some decrease in the aromaticity of the carbon backbone. The charge concentrations accounted for by the Laplacian of the electron density and the quadrupole polarization of the ipso C atoms provide an explanation for their reactivity in electrophilic substitution reactions. The steric strain in paracyclophanes was analyzed in terms of the forces exerted on the electron density, the Ehrenfest forces. This analysis did not provide any evidence of repulsive forces taking place in the molecules. In particular, the aromatic rings in [2.2]paracyclophane are highly aromatic, with an important electron delocalization between aromatic rings and forces that are always attractive.

Stimuli-responsive brush-shaped conjugated polymers with pendant well-defined poly(vinyl ether)s

For the synthesis of brush-shaped conjugated polymers consisting of a poly(phenylene butadiynylene) backbone and well-defined poly(vinyl ether) (polyVE) side chains, we designed polyVE-based macromonomers bearing a diethynyl benzene group at the terminus and applied them to the grafting through synthesis. The macromonomer (DE-PIBVE) was synthesized by living cationic polymerization of isobutyl VE (IBVE) using a functionalized initiator (TMS-DEVE-TFA) having a TMS protected diethynyl benzene moiety, followed by deprotection of the TMS groups. As a result, we succeeded in the synthesis of the target brush-shaped conjugated polymers [poly(DE-PIBVE)] by oxidative coupling reaction of the diethynyl benzene groups. We found that the solution of poly(DE-PIBVE) with a specific side chain length exhibited solvatochromism and thermochromism depending on the polarity of the media employed. This phenomenon was attributed to self-assembly in polar media due to the intermolecular π–π interaction between neighboring conjugated polymer backbones, where the self-assembly behavior would be closely related to the pendant polyVE structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3318–3325

Molecular structure of gaseous isatin as studied by electron diffraction and quantum chemical calculations

The molecular structure of isatin, indole-2,3-dione, was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (M062X and MP2 methods with aug-cc-pVTZ basis set). The best fit of the experimental scattering intensities (R-factor = 4.4%) was obtained for a molecular model of Cs symmetry. The structure of the benzene ring deviates from a regular hexagon due to the adjacent pyrrole heterocycle. The small differences between similar geometric parameters were constrained at the values calculated at the M062X level. The experimental structural parameters agree well with the results of theoretical calculations. The bonds in the benzene moiety are in agreement with their standard values. The (O)CC(O) carbon-carbon bond of the pyrrole moiety (1.573(7) Å) is remarkably lengthened in comparison with standard C(sp2)C(sp2) value, 1.425(11) Å for N-methylpyrrole. According to NBO analysis of isatin, glyoxal and pyrrole-2,3-dione molecules this lengthening cannot be attributed to the steric interactions of CO bonds alone and is, mainly, due to the electrostatic repulsion and hyperconjugation that is delocalization of oxygen lone pairs of π-type into the corresponding carbon-carbon antibonding orbital, nπ(O) → σ∗(CC). Deletion of σ∗(CC) orbital followed by subsequent geometry optimization led to shortening of the corresponding CC bond by 0.06 Å. According to different aromaticity descriptors, aromaticity of benzene moiety of isatin is smaller in comparison with benzene molecule. External magnetic field induces diatropic ring current in benzene moiety of isatin.

Ultraviolet fluorescence of coelenteramide and coelenteramide-containing fluorescent proteins. Experimental and theoretical study

Coelenteramide-containing fluorescent proteins are products of bioluminescent reactions of marine coelenterates. They are called ‘discharged photoproteins’. Their light-induced fluorescence spectra are variable, depending considerably on external conditions. Current work studies a dependence of light-induced fluorescence spectra of discharged photoproteins obelin, aequorin, and clytin on excitation energy. It was demonstrated that photoexcitation to the upper electron-excited states (260–300nm) of the discharged photoproteins initiates a fluorescence peak in the near UV region, in addition to the blue-green emission. To characterize the UV fluorescence, the light-induced fluorescence spectra of coelenteramide (CLM), fluorophore of the discharged photoproteins, were studied in methanol solution. Similar to photoproteins, the CLM spectra depended on photoexcitation energy; the additional peak (330nm) in the near UV region was observed in CLM fluorescence at higher excitation energy (260–300nm). Quantum chemical calculations by time depending method with B3LYP/cc-pVDZ showed that the conjugated pyrazine-phenolic fragment and benzene moiety of CLM molecule are responsible for the additional UV fluorescence peak. Quantum yields of CLM fluorescence in methanol were 0.028±0.005 at 270–340nm photoexcitation. A conclusion was made that the UV emission of CLM might contribute to the UV fluorescence of the discharged photoproteins. The study develops knowledge on internal energy transfer in biological structures – complexes of proteins with low-weight aromatic molecules.

Intramolecular π–π Interactions in Diethanodihydronaphthalene and Derivatives: Dynamic and Static Behavior of the Interactions Elucidated by QTAIM Dual Functional Analysis

AbstractDynamic and static behavior of the intramolecular π–π interactions between ethylene moieties in diethanodihydronaphthalene (1 a) and the derivatives (2 a–12 a) are elucidated by employing QTAIM‐DFA (QTAIM dual functional analysis), which we proposed recently. Total electron energy densities Hb(rc) are plotted versus Hb(rc) – Vb(rc)/2 at bond critical points (BCPs) for the interactions in question in QTAIM‐DFA, where Vb(rc) are potential energy densities at BCPs. After analysis of the plots, the π–π interactions in 1 a–12 a are all classified by the pure closed shell interactions and characterized to have the vdW nature with MP2/6‐311G(d), except for those in 10 a–12 a, where the ethylene moieties in 1 a are replaced by benzene moieties. The character in 10 a–12 a is predicted to have the typical‐HB (hydrogen bond) nature without covalency, although that in 10 a and 11 a seems close to the border area between the two. Indeed, the twisted structures were predicted for 1 a–4 a with MP2/6‐311G(d), but the observed non‐twisted structures of 1 a–3 a were better reproduced with MP2/6‐311G(3d). The typical‐HB nature without covalency was additionally predicted for the interactions between ethylene and benzene moieties in 9 a with MP2/6‐311G(3d), maybe due to somewhat shorter distances predicted for the interactions in question. The interaction in TS is also discussed exemplified by 10 a (C2v).

Dual Behavior of Iodine Species in Condensation of Anilines and Vinyl Ethers Affording 2-Methylquinolines.

A metal-free, mild and efficient method for the synthesis of 2-methylquinolines was successfully developed by condensation of anilines with vinyl ethers in the presence of catalytic amount of iodine. Modification of both pyridine and benzene moieties was easily achieved by changing only the vinyl ether and aniline. In this reaction, the iodine species was revealed to show dual behavior; molecular iodine serves as an oxidant, while its reduced form, hydrogen iodide, activates the vinyl ether. The redox reaction between these iodine species enables the use of a catalytic amount of iodine in this synthetic method.

Improving Performance and Stability of Flexible Planar‐Heterojunction Perovskite Solar Cells Using Polymeric Hole‐Transport Material

For realizing flexible perovskite solar cells (PSCs), it is important to develop low‐temperature processable interlayer materials with excellent charge transporting properties. Herein, a novel polymeric hole‐transport material based on 1,4‐bis(4‐sulfonatobutoxy)benzene and thiophene moieties (PhNa‐1T) and its application as a hole‐transport layer (HTL) material of high‐performance inverted‐type flexible PSCs are introduced. Compared with the conventionally used poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), the incorporation of PhNa‐1T into HTL of the PSC device is demonstrated to be more effective for improving charge extraction from the perovskite absorber to the HTL and suppressing charge recombination in the bulk perovskite and HTL/perovskite interface. As a result, the flexible PSC using PhNa‐1T achieves high photovoltaic performances with an impressive power conversion efficiency of 14.7%. This is, to the best of our knowledge, among the highest performances reported to date for inverted‐type flexible PSCs. Moreover, the PhNa‐1T‐based flexible PSC shows much improved stability under an ambient condition than PEDOT:PSS‐based PSC. It is believed that PhNa‐1T is a promising candidate as an HTL material for high‐performance flexible PSCs.

New series of N-aryl- and N-heteroaryl-d-glucuronamides as potential anticancer agents: synthesis and spectroscopic analysis

A series of structurally diverse d-glucuronic acid derivatives, comprising various aromatic scaffolds, was prepared and characterized with the aim of developing new prodrug candidates. The presented ultrasound-assisted protocol provides a convenient way for the synthesis of N-aryl- and N-heteroaryl-substituted d-glucuronamides with improved bioavailability. New conjugates containing benzene, naphthalene, indole, quinoxaline, and benzothiazole moieties were prepared in high yields (41–85%). Their structures were elucidated by various spectroscopic methods, including NMR, and their potential in the photoactivation of molecular oxygen was monitored by EPR spectroscopy. The application of the presented approach for the synthesis of potentially biologically active compounds makes the method attractive because of their potential use in biomedical and pharmaceutical chemistry.

Development of Self‐Doped Conjugated Polyelectrolytes with Controlled Work Functions and Application to Hole Transport Layer Materials for High‐Performance Organic Solar Cells

A series of anionic self‐doped conjugated polyelectrolytes (CPEs) by copolymerization of a 1,4‐bis(4‐sulfonatobutoxy)benzene moiety with different counter monomers of thiophene, bithiophene, and terthiophene is reported. The CPEs show high conductivity of ≈10−4 S cm−1 due to being self‐doped in a neutral state and exhibit excellent hole transporting property in the out‐of‐plane direction, compared with poly(3,4‐ethylenedioxythiophene):poly(styrene‐sulfonate) (PEDOT:PSS). Moreover, the CPE incorporating a less electron‐donating unit from terthiophene to thiophene exhibits a higher work function and therefore, PhNa‐1T incorporating thiophene shows a relatively high work function of 5.21 eV than 4.97 eV of PEDOT:PSS. This can induce a higher internal field in the solar cell device, facilitating efficient charge collection to the electrode. As a result, polymer solar cell devices incorporating the CPEs as a hole transporting layer achieve enhanced photovoltaic performances from those of the conventional PEDOT:PSS‐based devices. The solar cell efficiency reaches up to 9.89%, which is among the highest values demonstrated by PCE‐10‐based normal‐type organic solar cells.

Optically Active Cyclic Compounds Based on Planar Chiral [2.2]Paracyclophane with Naphthalene Units

AbstractTwo optically active cyclic compounds based on a planar chiral [2.2]paracyclophane core and containing either benzene or naphthalene moieties at the four corners of the structures were synthesized. Their optical and chiroptical properties were investigated by UV/vis absorption, photoluminescence (PL), circular dichroism, and circularly polarized luminescence (CPL) spectroscopy, as well as by density functional theory calculations. The circularly polarized luminescence (CPL) performance of the naphthalene‐containing cyclic compound was high with a large molar extinction coefficient, good photoluminescence efficiency, and a good CPL dissymmetry factor.

ChemInform Abstract: Palladium(II)‐Catalyzed C—H Acylation with Arylglycine Derivatives.

AbstractUsing the 2‐pyridyl group as directing group, novel regioselective ortho‐aryloylation of benzene moieties with arylglycins as acylation source has been developed.

Proton induced aggregation of water soluble isophthalic acid appended arylene diimides: justification with perylene derivative

We report the self-assembly behaviour of five water soluble arylene diimides based on benzene, naphthalene and perylene moieties, by utilizing the essentiality of two major reversible supramolecular interactions, π-stacking and hydrogen bonding.

Revealing the role of catechol moieties in the interactions between peptides and inorganic surfaces.

Catechol (1,2-dihydroxy benzene) moieties are being widely used today in new adhesive technologies. Understanding their mechanism of action is therefore of high importance for developing their applications in materials science. This paper describes a single-molecule study of the interactions between catechol-related amino acid residues and a well-defined titanium dioxide (TiO2) surface. It is the first quantified measurement of the adhesion of these residues with a well-defined TiO2 surface. Single-molecule force spectroscopy measurements with AFM determined the role of different substitutions of the catechol moiety on the aromatic ring in the adhesion to the surface. These results shed light on the nature of interactions between these residues and inorganic metal oxide surfaces. This information is important for the design and fabrication of catechol-based materials such as hydrogels, coatings, and composites. Specifically, the interaction with TiO2 is important for the development of solar cells.

Analysis of the magnetically induced current density of molecules consisting of annelated aromatic and antiaromatic hydrocarbon rings.

Magnetically induced current susceptibilities and current pathways have been calculated for molecules consisting of two pentalene groups annelated with a benzene (1) or naphthalene (2) moiety. Current strength susceptibilities have been obtained by numerically integrating separately the diatropic and paratropic contributions to the current flow passing planes through chosen bonds of the molecules. The current density calculations provide novel and unambiguous current pathways for the unusual molecules with annelated aromatic and antiaromatic hydrocarbon moieties. The calculations show that the benzene and naphthalene moieties annelated with two pentalene units as in molecules 1 and 2, respectively, are unexpectedly antiaromatic sustaining only a local paratropic ring current around the ring, whereas a weak diatropic current flows around the C-H moiety of the benzene ring. For 1 and 2, the individual five-membered rings of the pentalenes are antiaromatic and a slightly weaker semilocal paratropic current flows around the two pentalene rings. Molecules 1 and 2 do not sustain any net global ring current. The naphthalene moiety of the molecule consisting of a naphthalene annelated with two pentalene units (3) does not sustain any strong ring current that is typical for naphthalene. Instead, half of the diatropic current passing the naphthalene moiety forms a zig-zag pattern along the C-C bonds of the naphthalene moiety that are not shared with the pentalene moieties and one third of the current continues around the whole molecule partially cancelling the very strong paratropic semilocal ring current of the pentalenes. For molecule 3, the pentalene moieties and the individual five-membered rings of the pentalenes are more antiaromatic than for 1 and 2. The calculated current patterns elucidate why the compounds with formally [4n + 2] π-electrons have unusual aromatic properties violating the Hückel π-electron count rule. The current density calculations also provide valuable information for interpreting the measured (1)H NMR spectra.

The non-planarity of the benzene molecule in the X-ray structure of the chelated bismuth(III) heteroboroxine complex is not supported by quantum mechanical calculations.

The non-planarity of the benzene moiety in the crystal of a chelated bismuth(iii) heteroboroxine complex was not supported by DFT-D quantum chemical calculations. The observed bent structure of benzene is in fact a superimposition (thermal average) of the ensemble of thermally populated benzene structures in the complex studied.

In Search of the Antimicrobial Potential of Benzimidazole Derivatives.

A broad series of 4,5,6,7-tetrahalogenated benzimidazoles and 4-(1H-benzimidazol-2-yl)-benzene-1,3-diol derivatives was tested against selected bacteria and fungi. For this study three plant pathogens Colletotrichum sp., Fusarium sp., and Sclerotinia sp., as well as Staphylococcus sp., Enterococcus sp., Escherichia sp., Enterobacter sp., Klebsiella spp. , and Candida spp. as human pathogens were used. MIC values and/or area of growth reduction method were applied in order to compare the activity of the synthesized compounds. From the presented set of 22 compounds, only 8, 16, 18 and 19 showed moderate to good inhibition against bacterial strains. Against Candida strains only compound 19 with three hydroxyl substituted benzene moiety presented high inhibition at nystatin level or lower.

Donor–Acceptor-Type Semiconducting Polymers Consisting of Benzothiadiazole Derivatives as Electron-Acceptor Units for Organic Photovoltaic Cells

We synthesized two fused pentacyclic donor-acceptor structures, where the two different outer electron rich thiophene (DTPBT) and electron poor benzene (ICTh) moieties are covalently bonded to the central electron-deficient benzothiadiazole core by two nitrogen bridges. These new electron-acceptor DTPBT and ICTh building blocks were copolymerized with fluorene, as the electron donor group, via Suzuki coupling polymerization, to produce two new alternating copolymers, PFDTPBT and PFICTh, respectively. The average molecular weights of the synthesized polymers were determined by GPC. The number-average molecular weights of PFDTPBT and PFICTh were 19,000 (PDI = 2.5) and 20,000 (PDI = 4.0), respectively. The optical bandgap energies of the polymers were measured from their absorption onsets to be 2.15 and 2.55 eV, depending on the polymer structure. The HOMO energy levels of the polymers were determined, by measuring the oxidation onsets of the polymer films by cyclic voltammetry. The measured HOMO energy levels of PFDTPBT and PFICTh were -5.10 and -5.57 eV, respectively. When the polymers were blended with PC71BM, as the active layer for bulk-heterojunction photovoltaic devices, power conversion efficiencies were 2.08% and 0.34%, respectively, under AM 1.5 G (100 mW cm(-2)) conditions.

Synthesis and Electroluminescence Property of New Hexaphenyl Benzene Derivatives Including Emitting Core for OLED.

Three new emitting compounds of 5P-2TPA, 5P-2An and 5P-2Py for OLED based on hexaphenyl benzene moiety were synthesized. Physical properties were systematically examined by the change of the substitution groups of the synthesized materials. Photoluminescence (PL) spectrum of the synthesized materials showed maximum emitting wavelengths of about 437~488 nm in solution state and 457~516 nm in film state, indicating blue emission color. OLED devices were fabricated by the synthesized compounds using vacuum deposition process as an emitting layer. Device structure was ITO/2-TNATA 60 nm/NPB 15 nm/EML 35 nm/TPBi 20 nm/LiF 1 nm/Al 200 nm. External quantum efficiencies and CIE values of 5P-2TPA, 5P-2An and 5P-2Py were 3.34, 1.06 and 2.06% and (0.14, 0.12), (0.23, 0.45) and (0.24, 0.45), respectively. The three compounds exhibited thermal stablility with high Td of 426 °C, 449 °C and 467 °C.