Aromatic Skeleton Research Articles

Pre-biodrying treatment enhances lignin-related pathways with phenolic hydroxyls as reactive cores to accelerate humification during composting

The innovative biodrying-enhanced composting (BEC) process produces highly matured fertilizer within 10 d. To clarify the biodrying-accelerated humification mechanism, structural and molecular variations in humic acid (HA) during BEC were compared to those during 16-d bioaugmented mechanical composting without biodrying. Results showed that BEC produced HA with significantly higher aromaticity and molecular size (p < 0.01). More aromatic skeletons, mainly from biodrying-enhanced lignin decomposition (p < 0.05), contributed to HA aromatization. Reactive phenolic hydroxyls on these skeletons facilitated the binding of other humic precursors, promoting HA elongation. Microbial analysis indicated that Bacillus, Sinibacillus, and Issatchenkia, enriched by drastic heating and dehydration during days 0–3, participated in lignin decomposition. Saccharomonospora, Georgenia, Oceanobacillus, Nigrospora, Kluyveromyces, and Aspergillus contributed to HA elongation during the maturation phase (days 3–9). This study’s findings that biodrying enhanced lignin-related humification pathways by enriching functional microorganisms provides a theoretical foundation for further improving compost humification efficiency.

Formula Design of Hyperbranched Polyarylether‐Based Low Dielectric Photosensitive Resin and Study of UV‐Cured Films Properties

ABSTRACTFor large‐area electronic and high shape complexity structure applications, various solution‐processable materials are chosen as dielectric layer due to their simple molding process via spin‐coating, casting, or 3D printing at room temperature. Herein, the acrylic‐ended fluorinated hyperbranched polyaryletherketone (hb‐P6FAEK‐Ace) was used as the prepolymer and then, the composition of photosensitive resin formula was regulated by adjusting the addition ratio of hb‐P6FAEK‐Ace and diluents (acrylimorpholine [ACMO] 1,6‐Hexanediol diacrylate [HDDA]). These photosensitive resin solutions showed the relative low viscosities ranged ranging from 18 to 253 mPa S at 100°C which was in favor of the future 3D printing method and printing accuracy. Then, the obtained UV‐cured films show the maximum tensile strength up to 71.9 MPa and superior thermal properties with the Tg of 157°C–177°C and T5% of 314°C–351°C. Moreover, they also exhibited the good dielectric performance with dielectric constants of 2.43–2.20 and dielectric loss of 0.013–0.014 at 1 MHz–1 GHz. These abovementioned satisfactory performance could be ascribed to the aromatic skeleton of hb‐P6FAEK‐Ace, introduced polarizability‐CF3 groups and the inner cavities for the hyperbranched structures, also the precise control of formula composition. Additionally, the curing degree, shrinkage of solid, and moisture properties were also researched thoroughly. This work provides a simple formula design though to construct the high performance and low dielectric photosensitive resin for the requirements of microelectronic applications.

Interfacial oligomer splicing toward 3D silicon-centered polyimine nanofilm for rapid molecule/ion differentiation

3D porous organic polymers —renowned for rich interpenetrated, hierarchical pores and exceptional structural durability— showcase the potential for precise membrane-based separations. However, the challenge lies in processing these chemically stable polymers into a selective thin film under mild conditions. Herein, an interfacial oligomer splicing (IOS) approach via Schiff-base reactions is presented to create 3D silicon-centered porous polyimine (PPIn) nanofilms. The pre-synthesized oligomers from 4,4′,4″,4‴-silanetetrayltetrabenzaldehyde (TFS) and m-phenylenediamine (MPD) with high steric hindrance and hydrophobic character are precisely confined at the oil boundary, initiating IOS to yield an amorphous nanofilm on a Kevlar hydrogel surface. These silicon-centered 3D nanofilms exhibited an exceptional thermal and mechanical stability, while offering abundant low-resistance transport nanochannels. The nanofilm backbone, composed of rigid nonplanar aromatic skeleton and robust imine linkage, contributed to open and interpenetrated selective nanochannels, corroborated by both experimental and simulation and results. It was shown that 83-nm-thick PPIn nanofilms grown on the hydrogel achieved high-efficient molecule/ion differentiation, evident in excellent dye retention (>99.0 %), high NaCl permeation (92.8 %), and remarkable water permeability (74.3 L m−2 h−1 bar−1). This study establishes an innovative IOS approach for fabricating silicon-centered 3D-POP membranes and underscores their potential for efficient molecule/ion differentiation.

Exploring the graphitization transformation mechanism of deposited carbon in molten salt electrolysis: A novel insight from molecular structure models

Molten salt electrolysis graphitization is a novel method for the electrochemical graphitization, offering significant technological advantages. Researchers have shown keen interest in preparing graphite materials through molten salt strategies. However, there is still a lack of comprehensive research methodologies at the molecular scale for the removal of heteroatoms and rearrangement of carbon atoms in different amorphous carbon conversion systems. To address the above issue, the deposited carbon (DC, a coking byproduct) was converted into graphitized material (electrolysis products, EP) through the electrochemical method in this study. By processing Transmission Electron Microscope images with Python programming, aromatic skeleton structure information was quantitatively extracted. The evolution of the structure of DC was studied using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Based on information about elemental content, aromatic skeletal structure, and heteroatom functional groups, average chemical structure models were constructed for DC and EP, and relevant chemical bond parameters were statistically analyzed. Then, the influence of the electric field on the structural transformation of amorphous carbon in molten salts was investigated. The research results show that the electric field significantly affects the graphitization transformation process of amorphous carbon in molten salts, enhancing the interaction between calcium ions and DC molecules, increasing the diffusion coefficient of particles in the system, and promoting the formation of more sp2-hybridized carbon atoms, thus forming a more compact aromatic ring network. This study provides a new research method and molecular/atomic-level insights for a deeper understanding of the mechanism of graphitization transformation of amorphous carbon.

Combination of Cinnamaldehyde/β-cyclodextrin inclusion complex and L-phenylalanine effectively reduces the postharvest green mold in citrus fruit

The essential oil and β-cyclodextrin inclusion complex was able to inhibit the growth of Penicillium digitatum, a damaging pathogen that causes green mold in citrus fruit. In this study, cinnamaldehyde-β-cyclodextrin inclusion complex (β-CDCA) for controlling citrus green mold was synthesized by the co-precipitation method. Characterization of β-CDCA revealed that the aromatic ring skeleton of cinnamaldehyde (CA) was successfully embedded into the cavity of β-CD to form the inclusion complex. β-CDCA inhibited P. digitatum at a minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of 4.0 g/L. FT-IR spectroscopy analysis, calcofluor white staining, extracellular alkaline phosphatase (AKP) activity and propidium iodide (PI) staining of hyphae morphology showed that β-CDCA may damage the cell ultrastructure and membrane permeability of P. digitatum. The study further demonstrated that hydrogen peroxide (H2O2), malondialdehyde (MDA), and reactive oxygen species (ROS) markedly accumulated in 1/2 MIC β-CDCA treated hyphae. This implied that β-CDCA inhibited growth of P. digitatum by the triggering oxidative stress, which may have caused cell death by altering cell membrane permeability. In addition, in vivo results showed that β-CDCA alone or combined with L-phenylalanine (L-PHe) displayed a comparable level to that of prochloraz. Therefore, β-CDCA combined with L-PHe can thus be used as an eco-friendly preservative for the control green mold in postharvest citrus fruit.

Clypeasterol, a novel aromatic ergosterol skeleton from the mushroom Entoloma clypeatum

Chemical investigation of the wild mushroom Entoloma clypeatum led to the isolation of one new A-nor B-aromatic C28 steroid (1), along with eight known compounds (2–9) from this mushroom. As far as we know, compound 1 represents an unprecedented type of natural product. The structure of the new compound was elucidated based on extensive spectroscopic data analysis of HR-ESI-MS, 1D, and 2D NMR, while the relative configuration was confirmed by NOESY correlations. In addition, the anti-inflammatory activity of compound 1 was evaluated against LPS induced NO production in RAW 264.7 macrophages. Compound 1 exhibited a moderate anti-inflammatory activity with an IC50 value of 24.56 ± 1.72 μM.

Lignin Degradation by Klebsiella aerogenes TL3 under Anaerobic Conditions.

Lignin, the largest non-carbohydrate component of lignocellulosic biomass, is also a recalcitrant component of the plant cell wall. While the aerobic degradation mechanism of lignin has been well-documented, the anaerobic degradation mechanism is still largely elusive. In this work, a versatile facultative anaerobic lignin-degrading bacterium, Klebsiella aerogenes TL3, was isolated from a termite gut, and was found to metabolize a variety of carbon sources and produce a single kind or multiple kinds of acids. The percent degradation of alkali lignin reached 14.8% under anaerobic conditions, and could reach 17.4% in the presence of glucose within 72 h. Based on the results of infrared spectroscopy and 2D nuclear magnetic resonance analysis, it can be inferred that the anaerobic degradation of lignin may undergo the cleavage of the C-O bond (β-O-4), as well as the C-C bond (β-5 and β-β), and involve the oxidation of the side chain, demethylation, and the destruction of the aromatic ring skeleton. Although the anaerobic degradation of lignin by TL3 was slightly weaker than that under aerobic conditions, it could be further enhanced by adding glucose as an electron donor. These results may shed new light on the mechanisms of anaerobic lignin degradation.

Boron-, sulfur- and nitrogen-doped decacyclic multiple resonance emitters for narrowband deep blue electroluminescence

Two boron-, sulfur- and nitrogen-doped polycyclic aromatic hydrocarbon (PAH) multiple resonance (MR) emitters, namely mDBNS and mDBNStBu, are developed by introducing two pairs of boron (B) and sulfur (S) atoms at meta-positions of central benzene and one carbazole moiety in decacyclic aromatic skeletons. The resultant emitters exhibit efficient deep blue narrowband emission at 451–457 nm with full width at half maximum (FWHM) of 18–22 nm in toluene, together with PLQY of 70%–76% and reverse intersystem crossing rate (kRISC) of 1.1–1.2 × 105 s−1. Solution-processed organic light-emitting diodes (OLEDs) employing mDBNStBu as emitters exhibit deep blue electroluminescence at 462 nm with CIE coordinates of (0.13, 0.12), together with a maximum external quantum efficiency (EQEmax) of 10.4%.

All-Covalent Organic Framework Nanofilms Assembled Lithium-Ion Capacitor to Solve the Imbalanced Charge Storage Kinetics

HighlightsAn all-covalent organic framework (COF) nanofilm-structured lithium-ion capacitor (LIC) was developed by custom-made COF nanofilms as the anode/cathode.The COF nanofilm-structured LIC exhibits good electrochemical properties via the fast Li+ transport kinetics of the anodic COFBTMB-TP nanofilm and the high specific capacity of the cathodic COFTAPB-BPY nanofilm.This work can realize the charge storage kinetics and capacity balance of anode/cathode in COFTAPB-BPY//COFBTMB-TP LIC.

Fluorinated liquid crystals and their mixtures giving polar phases with enhanced low-temperature stability

ABSTRACT The fluid ferroelectrics, called ferroelectric nematics (NF), have recently become available by incorporating strong polarity into rod-shaped liquid crystal molecules. Its unprecedented electro-optic properties have created significant excitement in soft matter research. The further progression from the NF phase to the antiferroelectric smectic Z (SmZA) phase, and ultimately to the ferroelectric Smectic A (SmAF) phase, represents a remarkable journey in emerging polar liquid crystal states. Nevertheless, the limitation of NF liquid crystal materials remains one of the prominent obstacles to physical property optimization and optoelectronic device development. In this work, we synthesized a series of fluorinated liquid crystal molecules with large dipole moments and systematically investigated their phase behavior. We designed them with a similar fluorinated aromatic skeleton and varied the structures of the terminal group and bridging bond. We found that the dipole moment density and shape anisotropy significantly affect the phase behavior. Notably, diverse polar liquid crystal phases, including NF, SmZA, and SmAF were observed. Through a multi-component mixing strategy, we successfully achieved a much-expanded temperature window and improved low-temperature stability not only in the NF phase but also in the SmZA and SmAF phases.

Accessing Pyridines via a Nitrene Internalization Process

AbstractPyridines are valuable pharmacophores, and their access via direct and selective transmutation of carbon atom with desired nitrogen could become crucial in drug discovery processes. However, only scarce examples can be found when it comes C‐to‐N‐transmutation reactions of aromatics that could lead to the facile synthesis of pyridines or other azaarenes. In this context, Levin and co‐workers recently disclosed a process leading to pyridines from the corresponding aryl azides via the regioselective nitrene internalization process. Notably, the transformation did not lead to any further modification of the rest of the aromatic skeleton. This innovative work enabled selectively accessing various pyridine derivatives through direct nitrogen scan operations on benzene derivatives, which were otherwise not feasible.

Accessing Pyridines via a Nitrene Internalization Process.

Pyridines are valuable pharmacophores, and their access via direct and selective transmutation of carbon atom with desired nitrogen could become crucial in drug discovery processes. However, only scarce examples can be found when it comes C-to-N-transmutation reactions of aromatics that could lead to the facile synthesis of pyridines or other azaarenes. In this context, Levin and co-workers recently disclosed a process leading to pyridines from the corresponding aryl azides via the regioselective nitrene internalization process. Notably, the transformation did not lead to any further modification of the rest of the aromatic skeleton. This innovative work enabled selectively accessing various pyridine derivatives through direct nitrogen scan operations on benzene derivatives, which were otherwise not feasible.

Integration of covalent organic frameworks and molecularly imprinted polymers for selective extraction of flavonoid naringenin from grapefruit (Citrus × paradisi Macf.) peels

Grapefruit (Citrus × paradisi Macf.) peel, a by-product of the citrus-processing industry, possesses an important economic value due to the richness of bioactive compounds. In this study, boron-linked covalent organic frameworks integrated with molecularly imprinted polymers (CMIPs) were developed via a facile one-pot bulk polymerization approach for the selective extraction of naringenin from grapefruit peel extract. The obtained CMIPs possessed a three-dimensional network structure with uniform pore size distribution, large surface areas (476 m2/g), and high crystallinity. Benefiting from the hybrid functional monomer APTES-MAA, the acylamino group can coordinate with the boronate ligands of the boroxine-based framework to form B-N bands, facilitating the integration of imprinted cavities with the aromatic skeleton. The composite materials exhibited a high adsorption capacity of 153.65 mg/g, and a short adsorption equilibrium time of 30 min for naringenin, together with favorable selectivity towards other flavonoid analogues. Additionally, the CMIPs captured the template molecules through π–π* interaction and hydrogen bonding, as verified by FT-IR and XPS. Furthermore, they had good performance when employed to enrich naringenin in grapefruit peels extract compared with the common adsorbent materials including AB-8, D101, cationic exchange resin, and active carbon. This research highlights the potential of CMIPs composite materials as a promising alternative adsorbent for naringenin extraction from grapefruit peel.

Modified polyethyleneimine with abundant N/O/S-heteroatoms and aromatic segments: Convenient synthesis via sulfur-isocyanide-amine multicomponent reaction and application in high-performance iodine capture

With the continuous development of nuclear industry, the discharge of radioactive iodine (129I and 131I) become a potential danger to ecological environment. The development of high-performance iodine capture materials has important practical significance to reduce the harm of radioactive iodine. With the aim to construct new iodine-adsorbing polymer under the “bottom-up” structural designing guidance, using sulfur (S), branched polyethyleneimine (PEI) and 4,4’-oxybis(isocyanobenzene) (OBI) as starting substrates, a thiourea-modified PEI derivative (PEI-SIA) with abundant N/S/O-heteroatoms and aromatic molecular fragments was successfully prepared here via efficient sulfur-isocyanide-amine multicomponent polymerization (SIA-MCP). Characterization of PEI-SIA’s fundamental properties indicated that it is a new type of covalent organic polymer (COP). The iodine adsorption performance of PEI-SIA was systematically investigated. Experimental results showed that PEI-SIA can effectively adsorb iodine in steam (75 °C), cyclohexane, and aqueous phases, with the equilibrium adsorption capacities up to 6.48, 2.63, and 3.01 g g−1, respectively. The iodine adsorption mechanism of PEI-SIA was characterized by experimental investigation and Density Functional Theory (DFT) calculation. The results revealed that PEI-SIA’s high iodine adsorption performance can be attributed to the synergistic effect brought by N/S/O-containing segments and the electron rich aromatic skeletons in PEI-SIA.

Design of a bipolar organic small-molecule cathode with mesoporous nanospheres structure for long lifespan and high-rate Li-storage performance.

Organic small-molecule compounds have become promising cathode materials for high-performance lithium-ion batteries (LIBs) due to their high theoretical capacity, efficient utilization of active sites, low cost, and sustainability. However, severe dissolution and poor electronic conductivity limit their further practical applications. Herein, we have synthesized an insoluble organic small molecule, ferrocenyl-3-(λ1-azazyl) pyrazinyl [2,3-f] [1,10] phenanthrolino-2-amine (FCPD), by grafting ferrocene onto pyrazino[2,3-f] [1,10] phenanthroline-2,3-diamine (PPD). The combination of ferrocene (p-type Fe2+ moiety) and PPD (n-type C[double bond, length as m-dash]N groups) in a bipolar manner endows the target FCPD cathode with an increased theoretical capacity and a wide voltage window. The highly conjugated π-π aromatic skeleton inside enhances FCPD's electron delocalization and promotes strong interaction between FCPD units. Additionally, the mesoporous structure within the FCPD can provide numerous electroactive sites, contact area, and ion diffusion channels. Benefiting from the bipolar feature, aromatic, and mesoporous structure, the FCPD cathode demonstrates a large capacity of 250 mA h g-1 at 0.1 A g-1, a long lifespan of 1000 cycles and a high-rate capability of 151 mA h g-1 at 5 A g-1 along with a wide voltage window (1.2-3.8 V). Additionally, in situ synchrotron FT-IR and ex situ XPS reveal its dual ion storage mechanism in depth. Our findings provide essential insights into exploring the molecular design of advanced organic small molecules.

Design and synthesis of fluorine aromatic scaffolds containing drugs approved by the US FDA from 2002 to 2022

There are totally 93 fluorine aromatic scaffolds containing drugs approved by U.S. Food and Drug Administration from 2002 to 2022. The proportion of drugs containing fluorinated aromatic skeleton in approved drugs is increasing in recent ten years, which indicates the unique and important attributes of the fluorine atom. The introduction of fluorinated fragments into molecules can influence structure conformation, intrinsic potency and selectivity and pharmacokinetic properties productively. Additionally, 18F has been applied as a significant and useful positron emission tomography isotope for in vivo imaging technology. This review is mainly concentrated on the application and synthesis methods of 93 fluorine aromatic scaffolds containing drugs approved by the US FDA from 2002 to 2022. We hoped that this deep insight perspective into the synthetic methods for the delivery of these fluorine aromatic scaffolds containing drugs could offer practical and creative inspirations for the application and development of fluorine atom in new drug discovery.

Study on pyrolysis behavior of agricultural and forestry wastes using thermogravimetric‐Fourier transform infrared spectrometer (TG‐FTIR)

AbstractTo investigate the effective utilization of agricultural and forestry wastes for mitigating the shortage of primary energy and environmental pollution, the pyrolysis behavior of corn straw (CS), wheat straw (WS), and poplar sawdust (PS) was studied using thermogravimetric–Fourier transform infrared (TG‐FTIR) analysis. The activation energies and pyrolysis mechanism functions of different biomass types were calculated. The results showed that the functional group structures of the gaseous products generated from the pyrolysis of different biomass types were similar, mainly including OH, aliphatic CH, CO, aromatic ring skeleton, aromatic CH, and CO groups. These functional group structures mainly existed in oxygen‐containing compounds such as phenols, ketones, aldehydes, acids, esters, alcohols, and ethers. The pyrolysis process of agricultural and forestry wastes exhibited certain differences, with the PS undergoing thermal decomposition more easily, while the thermal decomposition mechanism functions of the two agricultural wastes (CS and WS) were similar. PS had a later initial release time for volatile matter, and the oxygen compounds produced by its pyrolysis were the highest, followed by WS and CS.

Synergistic effect triggered by Fe2O3 and oxygen-induced hydroxyl radical enhances formation of amino-phenolic humic-like substance

Metal oxides play a promising role in the transformation of polyphenols and amino acids involved in naturally occurring humification. The objective of this study was to explore the synergistic interactions between Fe2O3 and O2 in the formation of humic substances under a controlled O2 atmosphere (0%, 21% and 40% O2 levels). The results indicate that an O2 level of 21% with Fe2O3 was optimal for humic acid (HA) production. Hydroxyl radicals (∙OH) formed and promoted the formation of HA in the presence of O2, and O2 improved the enhancing capacity of Fe2O3 by oxidizing Fe(II) to Fe(III). Moreover, the combination of these processes resulted in a synergistic improvement in humification. The evolution of functional groups in HA suggested that O2 promoted the formation of oxygen-containing groups such as lipids, and Fe2O3 was conducive to the formation of dark-coloured polymers during the darkening process of humification. Furthermore, the O2 level of 40% inhibited the formation of HA by reducing the transformation from Fe(III) to Fe(II). The XRD results showed few changes in the composition of Fe2O3 before and after humification, which indicated that Fe2O3 was a catalyst and an oxidant. The heterospectral UV–Vis/FTIR results suggested that ∙OH attacked phenolic rings to form the aromatic ring skeleton of HA and benefit the ring-opening copolymerization of humic precursors. In addition, structural equation modelling demonstrated that dissolved Fe was the key parameter affecting the HA yield. These findings provide new insights into the synergism of O2-mediated ∙OH production associated with metal oxide-facilitated humification.

Evolution of structure and pyrolysis characteristics of coal tar residue after extraction

Coal tar residue (CTR) is a type of hazardous waste with potential utilization value. Pyrolysis is a promising thermal conversion technology, and a comprehensive knowledge regarding the pyrolysis behavior of CTR is crucial. In this study, the extract fraction (ECTR) and solid residual fraction (RCTR) of CTR are separated by toluene Soxhlet extraction. The structure features and pyrolysis characteristics of raw CTR, ECTR, and RCTR are investigated. The results shows that the ECTR is primarily composed of small molecule aromatics, aliphatic and aromatics with long alkyl side chains, branched alkyl or alicyclic structures. The condensed macromolecular aromatic carbon skeleton is remained in RCTR with some of the oxygenated structures exposed. The low volatile content and high aromaticity results in high thermal stability of RCTR, while the high fixed carbon content and carbonization product yield demonstrates its potential for high value-added applications. When postulated by Z(α) master plot, the reaction-order model fit best with the pyrolysis experimental data of CTR and its isolates. Both the Coats-Redfern (CR) model and Arrhenius model validate the reaction-order mechanism. The kinetic analyses reveals that the reaction order, activation energy and pre-exponential factor for RCTR all increased after extraction.

One-Step Synthesis of 7-Bromobenzo[c]chromeno[4,3,2-gh]phenanthridines through a Sequential Bromination/Cyclization/Aromatization Reaction Using N-Bromosuccinimide (NBS).

Herein, metal- and oxidant-free synthesis of 7-bromobenzo[c]chromeno[4,3,2-gh]phenanthridines is reported using N-bromosuccinimide. Sequential regioselective bromination, intramolecular ring cyclization, and aromatization reactions occur in a single step through a successive radical-catalyzed pathway. The mechanistic pathway for the cyclization is supported by a DFT study. Selective bromination in the fully aromatic skeleton is accomplished without involving additional aromatic electrophilic ring bromination. As a synthetic application, the Suzuki coupling reaction of compound 5a with boronic acid is reported to get compound 8a. Aggregation-induced emission of one of the synthesized compounds (5h) is also investigated in THF/hexane solvent along with concentration-dependent emission spectroscopy.