Search Results (133)

We present a theoretical model of the hydrogenation and amination of a primal carbon cluster of the tangled polycyclic type. Hydrogen atoms were introduced via H₂, while the nitrogen source was NH₃. The initial chemical processes were modeled using Born–Oppenheimer Molecular Dynamics. Metadynamics was employed to accelerate the saturation. The reactions were characterized in terms of barriers, topology, and intricate changes in the electronic structure. All transition states were identified. Multiple mechanisms for each type of reaction were discovered. Occasional unbiased changes in the carbon skeleton, induced by the guided processes, were observed. The initial addition reactions had no barriers due to the instability and high reactivity of the carbon structure. The final product of barrierless hydrogen saturation was C₂₅H₂₆. This molecule included multiple isolated double bonds, a medium-sized conjugated π system, and no triple bonds. Ammonia additions resulted in quaternary ammonium groups and primary amino groups. In the subsequent amination, a barrier appeared in fewer steps than in repetitive hydrogenation. The final product of barrierless saturation with NH₃ was C₂₅H₂(NH₃)₂NH₂. Further amination was characterized by a forward free-energy barrier of an order of magnitude larger than the reverse reaction, and the product was found to be unstable. Full article

We present a simple and cost-effective method for generating a dielectric barrier discharge (DBD) plasma using a commercially available ozone generator power supply. By coupling the plasma source to the extended ion transfer tube of an ambient mass spectrometer, we achieved stable plasma discharge, enabling the post-ionization of nonpolar compounds during the electrospray ionization process. Using this approach, we successfully detected polycyclic aromatic hydrocarbons (PAHs), halogenated PAHs (HPAHs), and other nonpolar pollutants in liquid mixtures, with detection limits on the order of 10 ng/mL. In fish exposed to HPAHs, both polar metabolites and lipids, as well as the nonpolar pollutant 1-chloronaphthalene, were simultaneously detected. Notably, 1-chloronaphthalene accumulated at the highest concentration in gill tissue. This straightforward plasma-assisted technique offers a reliable strategy for expanding the detection capabilities of electrospray mass spectrometry to include nonpolar molecules. Full article

The formation of polycyclic aromatic hydrocarbons (PAHs) during catagenesis does not exclusively lead to planar structures. The inclusion of five-ring elements increases the curvature of PAHs and yields bent molecules. These bowl-like configurations may end in the formation of spherical carbon allotropes as fullerenes or nanotubes, as recently shown. The presence of fullerenes in crude oil raises the question of why the reaction is feasible under catagenic conditions although the laboratory synthesis of fullerenes commonly requires high-energy environments. This study focuses on the feasibility of the simulation of catagenesis under laboratory conditions and the question of which building blocks may lead to spherical structures. Possible educts, reaction mechanisms, and conditions such as temperature are discussed and related to experimental outcomes. For the simulation under laboratory conditions, a light gas condensate was fractionated by distillation in order to reduce the number of compounds per fraction and make them distinguishable. The characterization of the resulting fractions was performed through GC-MS and GC-FID measurements before heat application in a closed reactor. High-resolution mass spectrometry (HRMS) measurements of the products indicated PAH growth and, more importantly, the formation of fullerenes. Interestingly, the characterized fullerenes mostly comprised the range of non-IPR (isolated pentagon rule) fullerenes. Full article

The lower and middle Carboniferous shale sequences are one of the important potential hydrocarbon source rocks in the piedmont of the southwestern Tarim Basin, China (PSTB). Rock samples were collected from the lower and middle Carboniferous formations on the Kushanhe, Altash, and Aitegou outcrops in the PSTB with the intention of mapping the hydrocarbon molecules within these shale sources and disclosing the relevant geochemical implications. The ratios of Pr/Ph < 1.0 and DBT/P < 0.4 and the enrichment of C₂₃ tricyclic terpanoid indicate that the Carboniferous shale sources were deposited in a reducing and sulfate-poor marine setting with the contribution of terrestrial freshwater. Marine aquatic algae act as the major contributor, resulting in the formation of Type II₁ kerogen. The Carboniferous shale sequences contain abundant diamondoids with 2–4 cages with the predominance of methyldiamantanes, dimethyldiamantanes, and methyltriamantanes. Quantitative extended diamondoid analysis indicates the occurrence of carbonate-rich and carbonate-poor organic facies in the PSTB. Compared to the carbonate-poor facies, the carbonate-rich facies is relatively depleted in C₂₇ diasteranes and rich in gammacerane, C₂₇ regular steranes, and alkylated triamantanes. This indicates that it was deposited in the more salty and stratified water column but with less input of land higher plants. The clay catalysis effects are assumed to be responsible for the discrepancy in steranes and diamondoids. The Carboniferous shale sequences also contain abundant polycyclic aromatic hydrocarbons with 2–5 rings with the predominance of C_0–1-phenanthrenes, chrysenes, and benzofluoranthenes. Thermal maturity parameters associated with polycyclic aromatic hydrocarbons and diamondoids suggest that the Carboniferous shale sources have arrived at the late mature to highly mature stage. This study provides the detailed molecular fingerprints of the lower and middle Carboniferous shale source sequences and explores the underlying geochemical implications. This should be helpful for oil–oil and oil–source correlations and hence petroleum exploration activity in the PSTB. Full article

Imidazole is a five-membered heterocyclic system featuring two nitrogen heteroatoms at the 1- and 3-positions of the ring. The imidazole scaffold is particularly suited for kinase inhibition concepts. This further confirms that this scaffold is a privileged structure in the development of anticancer drugs. Considering these key factors and the recent focus of scientists on imidazole compounds, we discuss the anticancer activities of imidazole-containing hybrids and related compounds, highlighting articles published in 2023 that serve as a basis for medicinal chemistry leads. From a chemical perspective, the present review emphasizes hybrid molecules with an imidazole ring in the side chain, imidazole-centered hybrid molecules, condensed imidazole hybrids, hybrid compounds containing two or more imidazole rings, polycyclic imidazole hybrids, imidazole-containing metal complexes, and benzimidazole hybrids. Full article

The efficient utilization of heavy oil is of great significance to alleviating the global energy crisis. How to efficiently convert heavy oil into high-value-added light fuel oil has become a hot issue in the field of petrochemicals. As the residual part of crude oil processing, heavy oil has a complex composition and contains polycyclic aromatic hydrocarbons, long-chain alkanes, and heteroatom compounds, which makes it difficult to process directly. Zeolite, as an important type of solid acid catalyst, has a unique pore structure, adjustable acidity, and good thermal stability. It can promote the efficient cracking and conversion of heavy oil molecules, reduce coke formation, and improve the yield and quality of light oil products. This paper systematically reviews the development status of heavy oil cracking technology, focusing on the structural characteristics, acidity regulation of zeolite catalysts, and their applications in heavy oil cracking and hydrocracking. The mechanism of the cracking reaction of polycyclic aromatic hydrocarbons and long-chain alkanes is analyzed in detail, and the catalytic characteristics and modification methods of zeolite in the reaction process are explained. In addition, this paper summarizes the main challenges faced by zeolite catalysts in practical applications, including uneven acidity distribution, limited pore diffusion, and easy catalyst deactivation, and proposes targeted development strategies. Finally, this paper looks forward to the future development direction of zeolite catalysts in the field of heavy oil cracking and upgrading reactions, emphasizes the importance of structural optimization and multi-scale characterization, and provides theoretical support and practical reference for the design and industrial application of efficient zeolite catalysts. Full article

Pyridazin-3(2H)one-based molecules have always attracted the attention of medicinal chemists due to their different pharmacological properties. The incorporation of such nuclei in therapeutically active molecules either as monocyclic units or as fused bi- or tricyclic scaffolds results in a wide range of pharmacological effects such as anti-inflammatory, analgesic, anticancer, antimicrobial, antiviral, cardiovascular-protective, antiulcer, and many other useful pharmacological activities. In accordance with our consolidated experience gained over the years in the chemistry and biology of tricyclic pyridazin-3(2H)ones, this review summarizes SAR studies of such pyridazinone-based polycyclic compounds endowed with various biological and therapeutic properties. Full article

The synthesis of three biaryl systems containing the benzo[1,2-b:4,3-b’] framework was accomplished through the Suzuki–Miyaura cross-coupling reaction between 1-bromobenzo[1,2-b:4,3-b’]dithiophene and easily available polycyclic aromatic hydrocarbon boronic acid pinacol esters containing pyrene, fluorene, and fluorenone. The spectroscopic characterization of these molecules was carried out by means of NMR experiments and high-resolution mass spectrometry. UV-vis absorption measurements at different concentrations of the newly synthesized compounds were also performed. Full article

Azulene-based polycyclic hydrocarbons have garnered much attention as potential materials for organic optoelectronic devices and as molecular models for graphene nanosheets with structural defects. Although various methods for ring fusions to an azulene core have been established for ring fusions to an azulene core, efficient synthetic methodologies for ortho- and peri-fusion to an azulene core are still lacking, which hinders the investigation of the effect of the ortho- and peri-fusion on the electronic properties of the embedded azulene core. Herein, we describe the synthesis and characterization of quinoxaline-fused cyclopenta[cd]azulene 4 as a new ortho- and peri-fused azulene derivative. The target molecule 4 was successfully synthesized in four steps from 4-methylazulene. The ring annulation decreased the lowest excitation energy compared with that of azulene and its structural isomer 5 and led to multiple reversible reduction processes. Characterization of the molecular geometry and optoelectronic properties of 4 revealed that the embedded azulene core preserves its original aromaticity, while the fused quinoxaline acts as a nucleophilic and basic site. These features suggest that 4 could serve as a metal ligand, a near-infrared absorber, and a component in organic functional devices. Full article

Bioremediation induced by bacteria offers a promising alternative for the contamination of aromatic hydrocarbons due to their metabolic processes suitable for the removal of these pollutants, as many of them are carcinogenic molecules and dangerous to human health. Our research focused on isolating a bacterium from the rhizosphere of the tara tree with the ability to degrade polycyclic aromatic hydrocarbons, using draft genomic sequencing and computational analysis. Enterobacter sp. strain UNJFSC 003 possesses 4460 protein-coding genes, two rRNA genes, 77 tRNA genes, and a GC content of 54.38%. A taxonomic analysis of our strain revealed that it has an average nucleotide identity (ANI) of 87.8%, indicating that it is a new native Enterobacteria. Additionally, a pangenomic analysis with 15 strains demonstrated that our strain has a phylogenetic relationship with strain FDAARGOS 1428 (Enterobacter cancerogenus), with a total of 381 core genes and 4778 accessory genes. Orthologous methods predicted that strain UNJFSC 003 possesses genes with potential for use in hydrocarbon bioremediation. Genes were predicted in the sub-pathways for the degradation of homoprotocatechuate and phenylacetate, primarily located in the cytoplasm. Studies conducted through molecular modeling and docking revealed the affinity of the predicted proteins in the degradation of benzo[a]pyrene in the homoprotocatechuate sub-pathway, specifically hpcB, which has enzymatic activity as a dioxygenase, and hpcC, which functions as an aldehyde dehydrogenase. This study provides information on native strains from Lomas de Lachay with capabilities for the bioremediation of aromatic hydrocarbons and other compounds. Full article

Antimicrobial resistance (AMR) poses a critical global health threat, driving the search for alternative treatments to conventional antibiotics. In this study, the antibacterial properties of honeybee venom (BV) and fungal Monascus purpureus red dye (RD) were evaluated against three multidrug-resistant bacterial pathogens. Extracts of BV and RD exhibited dose-dependent antibacterial activity against the three tested bacteria, with their strongest effectiveness against S. aureus (minimum inhibitory concentrations [MIC] = 3.18 and 6.315 μg·mL⁻¹, respectively). Although the three bacterial strains were resistant to the antibiotic ampicillin-sulbactam (10/10 µg), both extracts exhibited superior antibacterial activity against the three bacterial strains compared to five standard antibiotics, especially RD extract, which produced the largest inhibition zone (20 ± 0.20 mm) against S. aureus. The larger inhibition zones against S. aureus suggest its high sensitivity, whereas E. coli and E. faecalis exhibited smaller inhibition zones, indicating less sensitivity to BV and RD extracts. Differences in the inhibition zones suggest the variations in antimicrobial activity between the two extracts and their strain-specific effectiveness. Scanning electron microscopy (SEM) revealed that BV and RD extracts disrupted the bacterial plasma membrane, suggesting that the bioactive compounds penetrate the bacterial cell wall and alter its integrity. Furthermore, GC–MS-based analysis revealed that the chemical composition of BV and RD extracts exhibited highly diverse structures, including complex polycyclic systems, porphyrins, steroids, and esters. For instance, 42 metabolites were identified in the BV extract, which mainly were organic and metal–organic compounds; however, only 23 molecules were identified in RD extract, which mainly were fatty acids and their derivatives. The diversity in the chemical compositions of both extracts highlights their potential applications in pharmaceuticals, materials, and biochemistry fields. Collectively, these findings indicate that honeybee venom and the red dye from M. purpureus have promising antibacterial properties and warrant further investigation as potential alternatives to conventional antibiotics. Further multi-ligand docking-based virtual screening studies are required to identify the most promising detected metabolite(s) within both BV and RD extracts. Full article

Alkynylallenes offer the varied reactivity patterns of two different multiple bond linkages either separately or in concert. Initially, a short overview of their syntheses, structures, rearrangement mechanisms and synthetic utility, especially when treated with transition metal reagents such as gold(I), silver(I), platinum metals or metal carbonyls, is presented. Subsequently, we focus on the particular case of 1,2-dien-5-ynes (propargylallenes), whereby the shortness of the single atom bridge, and the consequent proximity of the allenyl and alkynyl moieties, facilitates metal-mediated interactions between them. It is shown how these metals can coordinate to either the alkyne or the allene fragment, thus leading to different cyclisation or rearrangement products, dependent also on whether it is the proximal or the distal double bond of the allene that participates in the reaction. Dimerisation of bromo-substituted fluorenylideneallenes bearing silyl or ferrocenyl substituents can occur in either head-to-head or head-to-tail fashion, thereby yielding propargylallene derivatives that undergo unexpected and novel rearrangements, including the formation of molecules possessing unusually long carbon–carbon single bonds. Fluorenyl-bearing propargylallenes react with silver nitrate or iron carbonyl to form novel organic polycyclic systems. Finally, suggestions are offered for future advances in the area. Full article

Xanthione is a sulfated polycyclic aromatic hydrocarbon which exhibits unique anti-Kasha properties and substantial sensitivity to its medium. Due to this sensitivity however, this makes xanthione-based systems very difficult to simulate. Further, xanthione’s is understood to be come more photostable in the presence of a highly polar medium, however whether these photophysical properties could be taken advantage of for certain applications remains to be seen. In clarifying long-held beliefs of specific solvent effects, we apply a rigorous theoretical solvent analysis in both implicit and explicit solvent mediums to elucidate a more complete description of solvent polarity sensitivity in xanthione using both quantum chemical and molecular dynamics techniques. Not only was it found that explicit solvation methods are vital in an accurate description of the system, only a handful of explicit solvent molecules in the simulation are required to yield an appropriate electronic description. This short work is vital to devising future applications for xanthione-based and other quantum technologies, and is an important foundation stone on this journey. Full article

Recently, polycyclic arenes with positive curvature have gained increasing significance in the field of material chemistry. This study specifically explores the inversion barriers of a series of positively curved circulenes by using five-membered heterocycles integrated into the backbone of primitive [5]circulenes and [6]circulenes. For hetero[5]circulenes, where one benzenoid ring is replaced by a heterocycle, the inversion barriers exhibit a strong correlation with the rotary angles of the heterocycles, and larger rotary angles result in lower inversion barriers. Additionally, the aromaticity of the circulene undergoes a significant reduction during the inversion process. As the number n of replaced rings increases, the inversion barriers can be adjusted, demonstrating an almost linear relationship with n. In the case of hetero[6]circulenes, molecules bearing heterocycles with small rotary angles also show positive curvatures. Furthermore, we examine the relationship between the radii of the fitted sphere for the circulenes and the inversion barriers, revealing an intriguing inverse proportionality between the fourth power of the radius and the inversion barrier. We anticipate that this research will offer a fresh perspective on studies related to positively curved polycyclic arenes. Full article

Background/Objectives: In connection with previous work on V-shaped polycyclic thiazolo[5,4-f]quinazolin-9-one and [5,4-f]quinazoline derivatives that can modulate the activity of various kinases, the synthesis of straight thiazole-fused [4,5-g] or [5,4-g]quinazolin-8-ones and quinazoline derivatives hitherto undescribed was envisioned. Methods: An innovative protocol allowed to obtain the target structures. The synthesis of inverted thiazolo[4,5-h] and [5,4-h]quinazolin-8-one derivatives was also explored with the aim of comparing biological results. The compounds obtained were tested against a representative panel of eight mammalian protein kinases of human origin: CDK9/CyclinT, Haspin, Pim-1, GSK-3β, CK-1ε, JAK3, CLK1 and DYRK1A. Results and Conclusions: The results obtained show that the novel linear thiazoloquinazolines are not kinase inhibitors. The cytotoxicity of these newly synthesized compounds was assessed against seven representative tumor cell lines (human cancers: Huh7-D12, Caco-2, HCT-116, MCF-7, MDA-MB-231, MDA-MB-468 and PC-3). The majority of these novel molecules proved capable of inhibiting the growth of the tested cells. The 7-Benzyl-8-oxo-7,8-dihydrothiazolo[5,4-g]quinazolinones 5b and 6b are the most potent, with IC₅₀ values in the micromolar range. None of these compounds showed toxicity against normal cells. A larger program of investigations will be launched to investigate the real potential interest of such compounds in anticancer applications. Full article