Heteroaromatic Structures Research Articles

Constructing a gradient modulus interface layer on the surface of carbon fibers to enhance the mechanical properties of carbon fiber/epoxy composites at different temperatures

A gradient modulus interface layer was designed between the carbon fiber and the epoxy by grafting the rigid polymer PPENK and the flexible polymer PEI. The influence of the interfacial modulus on the mechanical performance of carbon fiber/epoxy composite at different temperatures was analyzed. At room temperature, compared with the desized CF composite, the mechanical properties (interfacial shear, interlaminar shear, flexural strength, flexural modulus, and impact strength) of CF-PPENK-PEI composites were increased by 32.2 %, 11.4 %, 34.8 %, 24.2 % and 20.3 %, respectively. This improvement was attributed to the interfacial phase PPENK-PEI, which improved the roughness and polarity of the CF surface, increased wettability with the matrix, and buffered and balanced the modulus discrepancy between the CF and the epoxy. Atomic force microscopy (AFM) was confirmed the existence of a gradient modulus interface layer in CF-PPENK-PEI/epoxy composites. Notably, at 180 °C, the interlaminar shear strength (ILSS), flexural strength and flexural modulus of the CF-PPENK composite increased by 86.7 %, 92.5 % and 113.0 %, respectively, compared with the commercial CF composite, indicating better thermomechanical stability due to PPENK rigid heteroaromatic structures, which can maintain a high modulus at elevated temperature. Additionally, the dynamic thermomechanical properties of the composites were demonstrated the outstanding thermomechanical stability of the CF-PPENK/epoxy composites interface. Overall, this work provides a theoretical basis for preparing CF composites for use in high-temperature fields.

DFT Meets Wave-Function Methods for Accurate Structures and Rotational Constants of Histidine, Tryptophan, and Proline.

A new computational strategy has been applied to the conformational and spectroscopic properties in the gas phase of amino acids with very distinctive features, ranging from different tautomeric forms (histidine) to ring puckering (proline), and heteroaromatic structures with non-equivalent rings (tryptophan). The integration of modern double-hybrid functionals and wave-function composite methods has allowed us to obtain accurate results for a large panel of conformers with reasonable computer times. The remarkable agreement between computations and microwave experiments allows an unbiased interpretation of the latter in terms of stereoelectronic effects.

High‐Performance Aqueous Zinc‐Organic Battery Achieved by Reasonable Molecular Design

AbstractAqueous zinc‐organic batteries are considered as a promising candidate for the large‐scale energy storage systems. However, there are some challenges, involving inferior cycle stability (<3000 cycles) and low working potential, which restrain their extensive applications. Therefore, reasonable molecular design of organics is highly required to construct high‐performance zinc batteries. Herein, chalcogen atoms are introduced into the 9,10‐anthraquinone (AQ) molecule, and the anthraquinone analogues with fused heteroaromatic structures are obtained with increased working potentials and energy densities. In particular, the benzo[1,2‐b : 4,5‐b’]dithiophene‐4,8‐dione (BDTD) is proposed as the promising cathode with a long‐term lifespan of up to 12000 cycles and outstanding rate performance. Its operation mechanism involves the reversible co‐coordination reaction of hydrated Zn2+and H+with carbonyl groups. Moreover, the good rate and cycle performance can be retained even with a high mass loading cathode (10 mg cm−2), which is close to the commercial level. This work will guide the exploration of zinc‐organic battery.

A Visible Light Ru-Catalyzed Photoredox Access to Substituted Dihydrofurans.

An efficient, visible light Ru(bpy)3Cl2-catalyzed method for the preparation of 2,3-dihydrofurans is reported. This approach employs 2-bromoketoesters as radical precursors and alkyl enol ethers as acceptors. The photoredox cycle furnishes an oxonium ion that is captured by an internal nucleophile to render the corresponding dihydrofurans. Moreover, the obtained products contain a versatile acetal moiety at C-2, allowing its transformation into a diverse variety of heteroaromatic and nonaromatic compounds. This method could serve as an important tool in the synthesis of complex tetrahydro- and dihydrofurans as well as heteroaromatic structures.

Effects of temperature and carrier gas on physico-chemical properties of biochar derived from biosolids

This study investigated the influence of temperature (400 ºC, 500 ºC and 600 ºC) and –carrier gas (N2 and CO2) on biochar yields, physicochemical, and structural attributes. Higher temperatures resulted in less functional groups, higher surface area and lower H/C and O/C ratios. The biochar produced under N2 environment was more alkaline and showed higher salinity whereas the biochar produced under CO2 environment had higher surface area. The FTIR spectra of biochar produced in CO2 atmosphere indicated the decrease of functional groups such as –OH, CO, –CONH– and CC with increasing pyrolysis temperature. However, the band intensity for Si–O–Si or Si–O–C and aromatic and hetero-aromatic structures were more prominent in biochar obtained in CO2 environment than N2 environment. The presence of calcium carbonate (CaCO3), quartz (SiO2) and magnesium calcite (MgCO3) in biosolids and their biochars was confirmed by XRD spectrum. The outcomes from this research, particularly the stark contrast in biochar characteristics due to the variation in production conditions, inform the tailoring of biochars prepared under different conditions to environmental applications.

Palladium‐Catalyzed Direct Diarylation of 2‐Benzyl‐1,2,3‐triazole: a Simple Access to 4‐Aryl‐ or 4,5‐Diaryl‐2‐benzyl‐1,2,3‐triazoles and Phenanthro[9,10‐d][1,2,3]triazoles

AbstractThe reactivity of 2‐benzyl‐1,2,3‐triazole in palladium‐catalyzed direct arylation was studied. The reaction conditions for the selective synthesis of 2‐benzyl‐4‐aryl‐1,2,3‐triazoles in moderate to high yields using phosphine‐free Pd(OAc)2 catalyst and inexpensive KOAc base have been found. Then, from these 4‐aryl‐1,2,3‐triazoles, the palladium‐catalyzed C−H bond functionalization of the C5‐position allowed the synthesis of the corresponding 4,5‐diarylated 2‐benzyl‐1,2,3‐triazoles. This selective 4,5‐diarylation of 2‐benzyl‐1,2,3‐triazole was successfully applied for the straightforward building of the π‐extended polycyclic heteroaromatic structures phenanthro[9,10‐d][1,2,3]triazoles through Pd‐catalyzed C4‐ and C5‐intermolecular arylations followed by Pd‐catalyzed C−H intramolecular arylation.

Light-induced in situ chemical activation of a fluorescent probe for monitoring intracellular G-quadruplex structures.

Light-activated functional materials capable of remote control over duplex and G-quadruplex (G4) nucleic acids formation at the cellular level are still very rare. Herein, we report on the photoinduced macrocyclisation of a helicenoid quinoline derivative of binaphthol that selectively provides easy access to an unprecedented class of extended heteroaromatic structures with remarkable photophysical and DNA/RNA binding properties. Thus, while the native bisquinoline precursor shows no DNA binding activity, the new in situ photochemically generated probe features high association constants to DNA and RNA G4s. The latter inhibits DNA synthesis by selectively stabilizing G4 structures associated with oncogenic promoters and telomere repeat units. Finally, the light sensitive compound is capable of in cellulo photoconversion, localizes primarily in the G4-rich sites of cancer cells, competes with a well-known G4 binder and shows a clear nuclear co-localization with the quadruplex specific antibody BG4. This work provides a benchmark for the future design and development of a brand-new generation of light-activated target-selective G4-binders.

Fused Heterocyclic Molecule-Functionalized N-Doped Reduced Graphene Oxide by Non-Covalent Bonds for High-Performance Supercapacitors.

Indole molecules with fused heteroaromatic structures can be adsorbed on the N-doped graphene surface through the π-π interaction. Therefore, the indole-functionalized N-doped graphene (InFGN) with mesopores is successfully fabricated by a simple hydrothermal method and subsequent vacuum freeze-drying process. The microstructure, thickness, element composition, pore structure, and electrochemical performance of InFGN are analyzed via SEM, TEM, AFM, BET, UV-vis, FT-IR, XPS, Raman, XRD, and electrochemical technologies. Since the five-membered aromatic heterocycles are electron-rich, the indole molecules fixed on the N-doped graphene surface can repair the structural defects generated by N doping. Electrochemical measurements show that the InFGN electrode highlights an excellent capacitance of 622.3 F g-1 at 2 A g-1 and a durable cycling life of 100.5% after 5000 charging/discharging cycle times. For further practical application, a symmetric device has been assembled by using InFGN electrodes, which realizes high-power and energy densities (18.8-20.6 Wh kg-1 at 800-8000 W kg-1). This study provides a shortcut for building green supercapacitors with enhanced energy storage performance.

Establishing a phthalocyanine-based crosslinking interphase enhances the interfacial performances of carbon fiber/epoxy composites at elevated temperatures

A novel phthalocyanine-based interphase with a higher crosslinking density and glass transition temperature (Tg) was designed to enhance the interfacial properties of the carbon fiber/epoxy composite at elevated temperatures. The crosslinking density and the Tg of the interphase were tailored by tetraaminophthalocyanine (TAPc) with abundant amine groups and rigid heteroaromatic structures coated on the surface of the carbon fibers. Characterizations of the fiber surface properties were performed before and after coating, including topography, surface chemistry and surface energy. A sharp improvement in the interfacial shear strength for TAPc-coated carbon fibers (CF-TAPc) of 127.3% was obtained compared to that of the commercial carbon fibers (CF-commercial) at 150 °C. The modulus of the carbon fiber composite at the interface was investigated by force-mode atomic force microscopy (AFM), which indicated that the interphase of the CF-TAPc was stiffer than that of CF-commercial at 180 °C. Following the experimental observations, the dynamic mechanical thermal properties were investigated to confirm the better thermomechanical stability of the CF-TAPc interphase. This strategy is based on multireactive sites and the stiff structures of TAPc that generate higher Tg and act as a buffer between the fiber and matrix to counteract the generation of stress in the interphase, resulting in increased interfacial shear strength at elevated temperatures.

Characterization of feedstock and biochar from energetic tobacco seed waste pyrolysis and potential application of biochar as an adsorbent

In this study, a material with great adsorption potential was obtained from the residual cake from the extraction of energetic tobacco seeds. This residual cake seed was characterized and subjected to pyrolysis in nitrogen flow, resulting in bio-oil and biochar. The biochar and the feedstock (waste cake of tobacco seeds) were characterized by several techniques (thermogravimetric analysis (TGA), elemental analysis infrared spectroscopy, scanning electron microscopy, inductively coupled plasma optical emission spectrometry (ICP-OES), the Brunauer Emmet Teller (BET) method, the Barret, Joyner, and Halenda (BJH) method and functional density theory (DFT)) for comparison and subsequent possible application of the biochar. The results of the ICP-OES analyses indicate that nitrogen, potassium and phosphorus are the most abundant elements in the biomass and biochar. The metals analysis indicated no toxicological effects for animal feed. IR analysis results show that the pyrolysis led to conversion and/or removal of the vast majority of functional biomass groups, resulting in inorganic matter and inert carbon. The XPS analysis of the biochar indicates nitrogenous heteroaromatic structures which are formed during the pyrolysis process. In this way, can contribute to the cation exchange capacity in soils and adsorption of contaminants. Lastly, this biochar has great potential for use as an adsorbent for small molecules (due to the presence of micropores) after its activation, with a specific area of 1800 m2 g−1, surprisingly high compared with other solids of this type. Thus, a high value-added material can be obtained from the residue.

On non-equilibrium thermodynamics approach for the analysis of membrane processes: a case study of pervaporation

A brief review of the application of non-equilibrium thermodynamics (NET) is presented and advantages of some results of NET for the analysis of membrane processes are discussed. The case study of evaporation through a membrane (pervaporation) is considered on the basis of simplest approach in the framework of linear NET. A few examples are presented for membranes on the basis of polymers of heteroaromatic structures (polyheteroarylenes).

Introduction of Trifluoroethylamine as Amide Isostere by C-H Functionalization of Heteroarenes.

A direct and efficient introduction of a trifluoroethylamine motif into various heteroaromatic structures, using a readily available xanthate S-[1-(N-acetylamino)-2,2,2-trifluoroethyl]-O-ethyl dithiocarbonate (5), is reported. Medicinally relevant trifluoroethylaminated heteroarenes containing a wide range of functional groups were successfully synthesized under mild conditions. This amide isostere could be introduced into both electron-rich and -poor heteroarenes to give the desired products in one step. The beneficial effect of camphorsulfonic acid (CSA) was also demonstrated with electron-deficient heteroarenes.

A new approach to improving flame retardancy, smoke suppression and anti-dripping of PET: Via arylene-ether units rearrangement reactions at high temperature

In order to avoid the serious melt-dripping problems caused by conventional phosphorus flame retardants, a new arylene-ether containing monomer named 2,2′-(4,4′-(1,4-phenylenebis(oxy))bis(4,1-phenylene))bis(oxy) diethanol (PBPBD) was synthesized and introduced into the PET main-chain via condensation polymerization. With the incorporation of arylene-ether units, the thermal stability and the char residue from combustion of flame-retardant-element-free copolyesters containing PBPBD (BDxPETs) increased dramatically. However, the crystallinity and melting temperature of these copolymers were lower than the same quantities for PET. Thermal degradation kinetic was investigated using the Ozawa-Flynn-Wall method, which illustrated that the apparent activation energy for decomposition of the copolyesters was enhanced with increasing the conversion and the content of PBPBD. Py-GC/MS results showed that the PBBPD structural units undergo rearrangement reactions at high temperature, and ultimately form conjugated heteroaromatic structures, which lead to the formation of stable char residues with unique “stick-shaped” micro-morphology. Due to these rearrangement reactions, BDxPETs showed an expected flame retardant performance and a reduction in smoke generation during combustion. For example, the LOI value for BD10PET was 28.4, and the total smoke production (TSP) was 10.4 m2, much smaller than that for PET, 18.8 m2. Moreover, melt-dripping was restricted.

Structure and Gas Transport Properties of Polybenzoxazinoneimides with Biquinoline Units in the Backbone

SummaryFour polymers with heteroaromatic structures were synthesized starting from dichloroanhydride of 2,2/‐biquinoline‐7,7/‐dicarboxylic acid. These are imide‐containing polyamic acid and product of its cyclization polybenzoxazinoneimide as well as complexes of these two polymers with Cu(I). Dense film membranes prepared from the four polymers were characterized in terms of their density and free volume. The gas permeabilities to H2, O2, N2, CO2, and CH4 of the four films and the selectivities in separations of industrially important gas pairs were determined. Polymer chemical structures, polymer free volumes, diffusion coefficients and the sizes of gas molecules were correlated with polymer permeabilities. The prepared and investigated polymers show very good separation properties located near the upper bound lines in Robeson's diagrams.

Bioinspired Oxidative Aromatizations: One-Pot Syntheses of 2-Substituted Benzothiazoles and Pyridines by Aerobic Organocatalysis

Heteroaromatic structures are abundant in bioactive natural products, medicines, and other functional materials. Oxidative aromatization is a common method for preparing heteroaromatic species from simple building blocks. A bioinspired method was developed using robust flavin mimics as organocatalysts that perform O2-fueled oxidations of 1,4-dihydropyridines to pyridines and benzothiazolines to benzothiazoles in high yields (>95%) and purity at ambient temperature in methanol. The efficient oxidative aromatizations facilitated one-pot multicomponent syntheses of pyridines (from various aldehydes, dicarbonyl compounds, and ammonium acetate, in yields ranging from 35 to 95%) and benzothiazoles (from 2-aminothiophenol and various aldehydes, in 78–95% yield) without metals or reactive stoichiometric oxidants. For most substrates, neutral conditions were effective. Hindered 4-substituted dihydropyridines that oxidized slowly were accelerated by selection of more electrophilic flavin catalysts and the addition ...

Fused Heteroaromatic Dihydrosiloles: Synthesis and Double-Fold Modification

An efficient method for the synthesis of fused heteroaromatic dihydrosiloles via Ni-catalyzed hydrosilylation/intramolecular Ir-catalyzed dehydrogenative coupling of the Si-H bond with the heteroaromatic C-H bond has been developed. The method is efficient for both electron-deficient and -rich heterocycles. It exhibits high functional group tolerance and good regioselectivity. Fused heteroaromatic dihydrosiloles can be smoothly halogenated and then oxidized or arylated. Application of these transformations allows obtaining highly functionalized heteroaromatic structures. A gram-scale synthesis of dihydropyridinosilole has also been accomplished using reduced amounts of Ni- and Ir-catalysts.

Fused Heteroaromatic Organic Compounds for High‐Power Electrodes of Rechargeable Lithium Batteries

AbstractOrganic redox compounds are emerging electrode materials for rechargeable lithium batteries. However, their electrically insulating nature plagues efficient charge transport within the electroactive bulk. Alternative to the popular solution of elaborating nanocomposite materials, herein we report on a molecular‐level engineering strategy towards high‐power organic electrode materials with multi‐electron reactions. Systematic comparisons of anthraquinone analogues incorporating fused heteroaromatic structures as cathode materials in rechargeable lithium batteries reveal that the judicious incorporation of heteroaromatics improves the cell performance in terms of specific gravimetric capacity, working potential, rate capability, and cyclability. Combination studies with morphological observation, electrochemical impedance characterization, and theoretical modeling provide insight into the advantage of heteroaromatic building blocks. In particular, benzofuro[5,6‐b]furan‐4,8‐dione (BFFD) bearing furan moeities shows a reversible capacity of 181 mAh g−1 when charged/discharged at 100C, corresponding to a power density of 29.8 kW kg−1. These results have pointed to a general design route of high‐rate organic electrode materials by rational functionalization of redox compounds with appropriate heteroaromatic units as versatile structural tools.

ChemInform Abstract: A Unified Access to Diverse Heteroaromatic Scaffolds Using the Radical Chemistry of Xanthates

AbstractReview: 50 refs.

A unified access to diverse heteroaromatic scaffolds using the radical chemistry of xanthates

The degenerate transfer of xanthates allows generally difficult radical transformations, such as intermolecular additions to unactivated alkenes and cyclisations onto aromatic and heteroaromatic rings, to be accomplished under very practical experimental conditions. This translates into numerous approaches for the construction or modification of heteroaromatic structures. The present report aims to provide a brief overview of the various synthetic possibilities, with particular emphasis on medicinally interesting families of compounds.

Radical Migration of Substituents of Aryl Groups on Quinazolinones Derived from N-Acyl Cyanamides

A newly designed radical cascade involving N-acyl cyanamides is reported. It builds on aromatic homolytic substitutions as intermediate events and leads to complex heteroaromatic structures via an unprecedented radical migration of a substituent on aryl groups of quinazolinones (hydrogen or alkyl). Mechanistic considerations are detailed, which allowed us to devise fine control over the domino processes. The latter could be predictably stopped at several stages, depending on the reaction conditions. Finally, a surgical introduction of a trifluoromethyl substituent on a quinazolinone was achieved via the reported migration.