Aromatic Heterocycles Research Articles

Biomarker characteristics of the heterocyclic and polycyclic aromatic hydrocarbons in the crude oils from West Siberian Basin, Russia: an implication for correlation with organic matter input, depositional environment and maturity

The distribution of aromatic hydrocarbon in sediments and oils is known to be affected by thermal maturity, source input and depositional conditions. Hence, the aromatic hydrocarbon fraction of four oil samples from different wells of the West Siberian Basin (central Russia) was investigated to determine the source of organic matter (OM), depositional environment and maturity of their source rocks. Biomarker ratios and parameters of aromatic compounds indicate that the studied oils were generated from clay-rich source rocks containing a mixed organic matter of marine and terrestrial origin, which were deposited in freshwater/deltaic to marine environmental settings under suboxic to relatively oxic conditions. Furthermore, the maturity-sensitive aromatic hydrocarbon parameters indicate that the source rocks are thermally mature, and in the peak to late maturity stage of the oil generation window. Oil–oil correlation results of various established aromatic biomarker proxies for organic matter origin, depositional environment and lithology suggests that the analyzed west Siberian Basin’s oils were generated from a variety of geological sources and can be grouped into two distinct oil families. The first oil family (group I) was generated from clay-rich source rock containing mixed organic matter with relatively high amounts of terrestrial plant input and deposited in a non-marine (freshwater/deltaic) environment under relatively oxic conditions, while the second oil family (group II) was derived from mixed organic matter with high marine OM input that was deposited in marine environment under suboxic conditions. The findings of the heterocyclic and polycyclic aromatics highlighted in this study can help for better understanding of the genetic ties between oils and their sources and have an impact on traditional hydrocarbon development in the Basin.

Multivariate optimization of a green procedure for determination of emerging polycyclic aromatic nitrogen heterocycles in PM2.5 from sites with different characteristics.

Emerging polycyclic aromatic nitrogen heterocycles (PANHs) contributes significantly to the health risk associated with inhaling polluted air. However, there is a lack of analytical methods with the needed performance to their determination. This study presents the optimization and validation for the first time of a green microscale extraction procedure for the determination of twenty-one PANHs, including carbazole, indole, and quinolone classes, in particulate matter (PM2.5) samples by gas chromatography-mass spectrometry. A simplex-centroid mixture design and full factorial design (23) were employed to optimize the following extraction parameters: type and volume of solvent, sample size, extraction time, and necessity of a cleanup step. Low limits of detection and quantification (LOD < 0.97pgm-3 and LOQ < 3.24pgm-3, respectively) were obtained in terms of matrix-matched calibration. The accuracy and precision of the method were adequate, with recoveries in three levels between 73 to 120% and intraday and interday relative standard deviations from 2.0 to 12.9% and 7.3 to 18.9%, respectively. The green character of the method was evaluated using the Analytical Greenness (AGREE) tool, where a score of 0.69 was obtained, indicating a great green procedure. The method was applied to PM2.5 samples collected from sites with different characteristics; the concentrations ranged from 69.3pgm-3 (2-methylcarbazole) to 11,874pgm-3 (carbazole) for individual PANHs and from 2306 to 24,530pgm-3 for ∑21PANHs. Principal component analysis (PCA) and hierarchical clustering enabled discrimination of the sampling sites according to the PANHs concentrations. The score plots formed two distinct groups, one with samples containing higher concentrations of PANHs, corresponding to sites with a major influence from diesel emissions, and another group with minor PANH contents, corresponding to sites impacted by emissions from urban traffic and industrial activities.

Emission of water soluble brown carbon from different combustion sources: optical properties and functional group characterisation

Brown carbon (BrC) has a large impact on the Earth’s radiative balance. This study examined BrC’s optical characteristics, chemical functional groups, and total organic carbon (TOC) in deposited particulate matter from combustion of biomass, fossil fuels, and mosquito coil. A UV–vis spectrophotometer was used to assess BrC’s optical properties, a TOC analyzer was used to quantify TOC, and attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR) was used to identify functional group. The light absorption properties (absorption coefficient (babs-BrC), mass absorption efficiency (MAE365), absorption angstrom exponent (AAE), and refractive index (kabs-BrC)) were determined. Among biomasses, wheat straw exhibited the greatest value of babs-BrC (27.26 × 103 ± 4.09 × 103 Mm−1) whereas maize straw had the lowest value of babs-BrC (7.38 × 103 ± 1.11 × 103 Mm−1). A higher light absorption coefficient at 365 nm suggested that chromophores contributed more to the process. AAE followed this sequence - mosquito coil (5.46 ± 0.82) > biomass (5.13 ± 1.45) > fossil fuels (2.85 ± 0.32). The highest value of MAE365 (0.99 ± 0.15 m2 gC−1) and kabs-BrC (0.028 ± 0.004) was obtained in wheat straw, whereas the lowest value of MAE365 (0.07 ± 0.011 m2 gC−1) and kabs-BrC (0.002) was identified in octane. Biomasses samples showed a strong peak at ∼850, ∼1368, ∼1370, ∼1306, and near 1640 cm−1, indicating that the major component of BrC was organic nitrate R-ONO2 which is responsible to increase the light absorption properties. It also contains complex heterocyclic aromatic ring compounds, carbonyl group (C=O), and nitrogen-containing groups such as −NO 2, C≡N. The projected substantial contribution of BrC to overall light absorption is one illustration of the probable climatic effect of biomasses and fossil fuel burning in Southeast Asian region.

Back Cover

The cover picture shows a domino ring opening and coupling reaction of aromatic tricyclic heterocycles with O2 at solvothermal condition, leading to 1,2‐diamidoalkenes derivatives. A series of techniques have been applied to track the reaction process in this gas‐liquid black‐box like system. A seven‐step domino sequence involving a peroxide intermediate has been proposed. This work may provide a unique strategy to develop and design domino reactions starting from heterocycles. More details are discussed in the article by Zeng et al. on page 2089—2094.image

Comparative analysis of organic chemical compositions in airborne particulate matter from Ulaanbaatar, Beijing, and Seoul using UPLC-FT-ICR-MS and artificial neural network

This paper presents comparative study on the composition and sources of PM2.5 in Ulaanbaatar, Beijing, and Seoul. Ultrahigh performance liquid chromatography (UPLC) combined with ultrahigh resolution mass spectrometry (UHR-MS) were employed to analyze 85 samples collected in winter. The obtained 340 spectra were interpreted with artificial neural network (ANN). PM2.5 mass concentrations in Ulaanbaatar were significantly higher than those in Beijing and Seoul. ANN based interpretation of UPLC UHR-MS data showed that aliphatic/lipid derived organo‑sulfur compounds, polycyclic aromatic and organo‑oxygen compounds were characteristic to Ulaanbaatar. Whereas, aliphatic/lipid-derived organo‑oxygen compounds were major components in Beijing and Seoul. Aromatic organo‑nitrogen compounds were the main contributors to differentiating the spectra obtained from Beijing from the other cities. Based on two-dimensional gas chromatography/high resolution mass spectrometric (GCxGC/HRMS) data, it was determined that the concentrations of the polycyclic aromatic hydrocarbon (PAH) and polycyclic aromatic sulfur heterocycle (PASH) containing sulfur were highest in Ulaanbaatar, followed by Beijing and Seoul. Coal/biomass combustion was identified as the primary source of contamination in Ulaanbaatar, while petroleum combustion was the main contributor to PM2.5 in Beijing and Seoul. The conclusion that diesel-powered heavy-duty trucks and buses are the main contributors to NOx emissions in Beijing is consistent with previous reports. This study provides a more comprehensive understanding of the composition and sources of PM2.5 in the three cities, with a focus on the differences in their atmospheric pollution profiles based on the UPLC UHR-MS and ANN analysis. It is notable that this study is the first to utilize this method on a large-scale sample set, providing a more detailed and molecular-level understanding of the compositional differences among PM2.5. Overall, the study contributes to a better understanding of the sources and composition of PM2.5 in Northeast Asia, which is essential for developing effective strategies to reduce air pollution and improve public health.

Dibenzothiophene removal by environmental bacteria with differential accumulation of intracellular inorganic polyphosphate

Dibenzothiophene (DBT), which belongs to the group of polycyclic aromatic heterocycles of sulfur, is a model substance to study the removal of sulfur compounds from oil due to its recalcitrance to traditional and specific removal processes. The aim of this work was to evaluate DBT bioremoval by environmental bacteria and its relationship with polyphosphate (polyP) accumulation, cell surface characteristics and bioemulsifying activity. Pseudomonas sp. P26 achieved the highest DBT removal percentage (48%) after 7 days of incubation. Moreover, positive correlations were estimated between DBT removal and bioemulsifying activity and biofilm formation. A strain-dependent relationship between the content of intracellular polyP and the presence of DBT in the culture medium was also demonstrated. The study of these bacterial characteristics, which could promote DBT transformation, is a first approach to select DBT-removing bacteria, in order to develop bioformulations that are able to contribute to desulfurization processes of petroleum-derived pollutants in the future.

Adsorptive desulphurization of fuels by hypercrosslinked nanoporous polymers derived from polycyclic aromatic hydrocarbons

A sustainable method is employed to remove polycyclic aromatic sulphur heterocycles (PASHs) from fuels by using a series of high surface area nanoporous adsorbents synthesized from polycyclic aromatic hydrocarbons (PAHs). The hypercrosslinking of PAHs has been used to synthesize high surface area (SABET of 620–1565 m2 g−1) nanoporous polymeric materials via a microwave assisted method. The adsorbent poly-naph (highest SABET, i.e., 1565 m2 g−1) display best performance for desulphurization of fuels from batch to fixed bed column mode. In batch mode, the adsorption capacity of 12.1 (up to 9 ppm sulphur) and 8.9 mgS g−1 (up to 43 ppm sulphur), has been estimated for model (100 ppm sulphur) and real fuels (110 ppm sulphur), respectively. Furthermore, from ultra-low sulphur model (10 ppm sulphur) and real fuel (9 ppm sulphur), the adsorption capacity of 16.1 (up to 0.3 ppm sulphur) and 10 mgS g−1 (up to 3 ppm sulphur) has been estimated. In fixed-bed column mode, the high concentrated model and real fuel have been desulphurized to final concentration of 1 and 12 ppm, respectively. While, at low concentrations, the final concentration of 100 ppb and 1 ppm is achieved for model and real fuels, respectively. The adsorption mechanism revealed that π-electron density in the polymeric framework plays prominent role in the adsorption process apart from high surface area. This approach to control carcinogenic aromatic pollutants like PAHs and PASHs can be sustained over time through technological advancement, financial assistance and governmental regulation.

Preparation of chitosan derivatives containing aromatic five-membered heterocycles for efficient antimicrobial and antioxidant activities

In this study, nine chitosan derivatives containing aromatic five-membered heterocycles were prepared and the effects of different grafting methods on the biological activities of chitosan derivatives were investigated. The structures of all the compounds were characterized by Fourier Transform Infrared (FT-IR) spectroscopy and Nuclear Magnetic Resonance (NMR) spectroscopy, while the antioxidant, antifungal and antibacterial activities of the chitosan derivatives were tested. The experimental data suggested that the chitosan derivatives had outstanding inhibitory ability against Fusarium graminearum, Fusarium oxysporum f.sp.cucumbrum, Staphylococcus aureus and Escherichia coli. At the same time, some of the compounds showed strong scavenging ability against DPPH radical and superoxide radical. Cytotoxicity experiments have demonstrated that some chitosan derivatives are non-toxic to L929 cells. More importantly, compared to chitosan, these chitosan derivatives have good water solubility and can be used as potential polymers for antifungal and antibacterial biomaterials in agriculture.

Quantification of polycyclic aromatic sulfur heterocycles in fine airborne urban particles (PM2.5) after multivariate optimization of a green procedure

Polycyclic aromatic sulfur heterocycles (PASHs), such as benzothiophenes (BT), dibenzothiophenes (DBT) and benzonapthothiophenes (BNT), can be emitted from vehicular traffic and deposited in fine particles matter (PM2.5). The presence of these compounds in PM2.5 is an environmental concern due to air pollution and its toxic properties. In this study, a green microscale solid–liquid extraction method was developed to determine twenty-three PASHs in PM2.5. A simplex-centroid mixture design was applied to optimize the extraction solvent. A full factorial design was used for preliminary evaluation of the factors that influence the extraction process (extraction time, sample size, and solvent volume) and then a Doehlert design for the significant parameters. The optimal extraction conditions based on the experimental design were: sample size, 4.15 cm2; 450 μL of toluene:dichloromethane (80:20,v/v); and extraction duration, 24 min. High sensitivity (LOD < 0.66pg m−3 and LOQ < 2.21 pg m−3) and acceptable recovery (82.8–120 %), and precision (RSD 3.6–14.0 %) were obtained. The greenness of the method was demonstrated using the Analytical GREEnness (AGREE) tool. The method was applied for analyzing PASHs in PM2.5 samples collected in three time intervals per day from years with different sulfur contents in the diesel: S-500 (≤500 ppm sulfur) and S-50 (≤50 ppm sulfur). Fourteen PASHs were quantified with the highest concentrations observed for 2,8-DMDBT and 4,6-DMDBT, which are recalcitrant compounds. The ANOVA test indicated significant differences between sampling periods during the day. The reduction of diesel S-500 to S-50 corresponded to a 28 % decrease in the total sum of PASHs (∑PASHs) evaluated. Spearman's rank correlations allowed for verifying that BTs and DBTs were highly correlated, suggesting that they were derived from similar sources. A weak correlation of 2,1-BNT and 2,3-BNT with BTs and DBTs indicates that these compounds are a chemical proxy for the emission of diesel engines during the combustion process.

Overcoming shielding in mass detection via isolation of sulfur heterocycles using green silver nanoparticles

AbstractSilver nanoparticles (nano‐Ag0) fixed on supports or in colloidal solution exhibit surface plasmon resonance, but there have been few attempts at surface plasmon resonance‐based liquid chromatographic separation. Here, for the first time, a capped Ag(I) green tea colloidal solution was used as a precursor to anchor nano‐Ag0 on silica. Nano‐Ag0 supported on silica was confirmed by spectroscopy and microscopy, and nano‐Ag0 particles (average diameter 20 nm) were scattered on the silica surface. This ecologically friendly approach for doping nanoparticles on solid supports was as efficient as chemical methods and could be used to separate polycyclic aromatic sulfur heterocycles from a heavy aromatic fraction. Using a nano‐Ag‐silica ligand exchanger, parts‐per‐million concentrations of sulfur heterocycles were probed by surface plasmon resonance nano‐Ag0 on a solid substrate. Using this approach, mass detection shielding can be eliminated to isolate polycyclic aromatic sulfur heterocycles from aromatic fractions. This study presents an innovative approach to producing dispersed silver nanoparticles on a solid substrate.

A sustainable management of polycyclic aromatic hydrocarbons to synthesize microporous organic polymers for adsorptive desulphurization of fuels

A sustainable management of carcinogenic polycyclic aromatic hydrocarbons (PAHs) to synthesize a series of high surface area (SABET of 563–1553 m2 g−1) microporous polymeric adsorbents is reported. The products with high yield (>90%) were obtained within only 30 min at a low temperature of 50 °C using a microwave-assisted approach with 400 W microwave power followed by 30 min of ageing by raising the temperature to 80 °C. The synthesized adsorbents are used for removing another category of carcinogenic pollutants i.e., polycyclic aromatic sulphur heterocycles (PASHs) from model and real fuels. Adsorptive desulphurization experiment in batch mode could reduce the sulphur from high concentrated model (100 ppm) and real (102 ppm) fuels to 8 ppm and 45 ppm respectively. Similarly, desulphurization of model and real fuels with ultralow sulphur concentrations of 10 and 9 ppm, respectively, reduced the final concentration of sulphur to 0.2 and 3 ppm, respectively. Adsorption isotherms, kinetics, and thermodynamic studies have been conducted using batch mode experiments. Adsorptive desulphurization using fixed bed column studies show the breakthrough capacities of 18.6 and 8.2 mgS g−1, for the same high concentrated model and real fuels, respectively. The breakthrough capacities of 1.1 and 0.6 mgS g−1 are estimated for the ultralow sulphur model and real fuels, respectively. The adsorption mechanism, based on the spectroscopic analysis (FTIR and XPS) demonstrates the role of π-π interactions between the adsorbate and adsorbent. The adsorptive desulphurization studies of model and real fuels from batch to fixed bed column mode would offer an in-depth understanding to demonstrate the lab-scale findings for industrial applications. Thus, the present sustainable strategy could manage two classes of carcinogenic petrochemical pollutants, PAHs and PASHs, simultaneously.

Turning the Imidazole Core into Three-Dimensional Ring Systems: Mild Organocatalytic Entry to Enantiopure 6,7-Dihydrobenzimidazoles.

Organocatalytic asymmetric transformation of common aromatic heterocycles via in situ formation of highly reactive dearomatized ortho-quinodimethane diene species and subsequent [4+2] cycloaddition with suitable dienophiles has become a powerful tool to enter cyclohexane-fused heterocycles. Most of these reactions were previously applied to benzo-fused heterocycles or poorly aromatic rings. Herein, we disclose how previously intractable aromatic imidazole rings, equipped with removable methylidene malononitrile activating handle, could be involved as competent cycloaddends with β-aryl enals in efficient eliminative [4+2] cycloadditions under mild organocatalytic conditions. This method allowed the efficient and direct preparation of scantly represented 6,7-dihydrobenzo[d]imidazoles with optimal enantio- and regioselectivities. Post-cycloaddition chemical editing provided imidazole-based ring systems with diverse oxidation state and functional groups.

Excited State Dynamics of Dibenzothiophene Derivatives.

Polycyclic aromatic sulfur heterocycles are environmental pollutants formed from incomplete combustion processes and crude oil spills. Their excited state dynamics are not understood. Herein, femtosecond transient absorption is combined with steady-state spectroscopy and computational methods to elucidate the relaxation mechanisms of three dibenzothiophene derivatives. The low-energy singlet and triplet states all have ππ* character in the Franck-Condon region, and two minima were located in the S1 surface. Excitation at 320 nm populates their S1 state directly, which relaxes with lifetimes ranging from 4 to 13 ps. Most of the S1 population undergoes efficient intersystem crossing to the triplet state with lifetimes ranging from 820 ± 50 to 900 ± 30 ps. The compounds exhibit negligible nonradiative internal conversion, low fluorescence yields of 1.2 to 1.6%, and triplet yields of ca. 98%. Linear interpolation of internal coordinates reveals the chemical basis for relaxing the spin-forbidden intersystem crossing in these π-aromatic systems.

Nanographene-Based Decoration as a Panchromatic Antenna for Metalloporphyrin Conjugates.

Porphyrins, a type of heterocyclic aromatic compounds consisting of tetrapyrroles connected by four substituted methine groups, are appealing building blocks for solar energy applications. However, their photosensitization capability is limited by their large optical energy gap, which results in a mismatch in absorption toward efficient harvesting of the solar spectrum. Porphyrin π-extension by edge-fusing with nanographenes can be employed for narrowing their optical energy gap from 2.35 to 1.08eV, enabling the development of porphyrin-based panchromatic dyes with an optimized energy onset for solar energy conversion in dye-sensitized solar fuel and solar cell configurations. By combining time-dependent density functional theory with fs transient absorption spectroscopy, it is found that the primary singlets, which are delocalized across the entire aromatic part, are transferred into metal centred triplets in only 1.2ps; and subsequently, relax toward ligand-delocalized triplets. This observation implies that the decoration of the porphyrin moiety with nanographenes, while having a large impact on the absorption onset of the novel dye, promotes the formation of a ligand-centred lowest triplet state of large spatial extension, potentially interesting for boosting interactions with electron scavengers. These results reveal a design strategy for broadening the applicability of porphyrin-based dyes in optoelectronics.

ON-OFF Fluorescent Cyanine Dye Based on a Benzothiophenyl Rotor Enables Selective Illumination of G-Quadruplexes in Mitochondria.

Conventional cyanine dyes exist as "always-on" fluorescent probes leading to inevitable background signals which often limit their performance and scope of applications. To develop specific fluorescent probes with high sensitivity and robust OFF/ON switching for targeting G4s, we introduced aromatic heterocycles through conjugation with polymethine chains to construct a rotor-π system. Here, a universal strategy is presented to synthesize pentamethine cyanines with different aromatic heterocycle substituents on the meso-polymethine chain. In these probes, SN-Cy5-S is self-quenched in aqueous solution due to H-aggregation. The structure indicates that SN-Cy5-S with a flexible meso-benzothiophenyl rotor conjugated to the cyanine backbone matches adaptively with G-tetrad planes, enhancing π-π stacking and resulting in triggered fluorescence. This allows recognition of G-quadruplexes due to the synergy of disaggregation-induced emission (DIE) and inhibited twisted intramolecular charge-transfer effects. This combination leads to a robust lighting-up fluorescence response for c-myc G4 with superior fluorescence enhancement (98-fold), allowing for a low detection limit of 1.51 nM, which is much more sensitive than the previously reported DIE-based G4 probes (22-83.5 nM). In addition, the superior imaging properties and rapid internalization time (5 min) in mitochondria allow SN-Cy5-S to also have a high potential for mitochondrially targeting anti-cancer therapy.

An Insight into the Recent Synthetic Approaches of Benzimidazole Motifs Based on Divergent Substrate Scope

Abstract: Simple heterocyclic moieties are quite famous in synthetic organic chemistry due to their bioavailability, ease of laboratory synthesis, and variety of applications in multidisciplinary fields. Benzimidazole is an N-containing benzofused chemical compound with the formula C7H6N2 and belongs to the family of heterocyclic aromatic organic compounds. It is a potent bioactive molecule with prominent therapeutic activities and found to have prior importance in medicinal chemistry. Several advanced investigations in this area also proved that benzimidazole and its derivatives have significant antimicrobial, antiparasitic, antifungal, and anti-carcinogenic activities. It has also gained popularity in material science as well. Because of its versatile applications, numerous research groups paid considerable attention towards the synthesis of benzimidazoles. o-Phenylenediamine (OPD) is considered as the traditional substrate for benzimidazole synthesis. In this review, we discussed the synthetic approaches of benzimidazoles from OPD as a primary reactant with diverse substrates like aldehydes, alcohols, carboxylic acids/esters, etc. We have also briefed up reactions which uses the primary substrates such as o-nitroanilines and o-dinitro benzenes. This review report covers research findings which are published from 2016 till date and describes numerous practical and greener methods of synthesis. It also narrates innovative biocatalysts, photocatalysts and nano-catalysts, which are used for the synthesis of benzimidazoles.

Metabolomics-Based Analyses of Dynamic Changes in Flavonoid Profiles in the Black Mulberry Winemaking Process.

To overcome the fruit's perishability, mulberry wine has been developed as a method of preservation. However, dynamic changes in metabolites during mulberry wine fermentation have not been reported yet. In the present investigation, UHPLC-QE-MS/MS coupled with multivariate statistical analyses was employed to scrutinize the metabolic profiles, particularly the flavonoid profiles, throughout the process of vinification. In general, the major differential metabolites encompassed organic heterocyclic compounds, amino acids, phenylpropanoids, aromatic compounds, and carbohydrates. The contents of total sugar and alcohol play a primary role that drove the composition of amino acids, polyphenol, aromatic compound, and organic acid metabolites based on the Mantel test. Importantly, among the flavonoids, abundant in mulberry fruit, luteolin, luteolin-7-O-glucoside, (-)-epiafzelechin, eriodictyol, kaempferol, and quercetin were identified as the differential metabolic markers during blackberry wine fermentation and ripening. Flavonoid, flavone and flavonol biosynthesis were also identified to be the major metabolic pathways of flavonoids in 96 metabolic pathways. These results will provide new information on the dynamic changes in flavonoid profiles during black mulberry winemaking.

Chemical structure and thermal maturation of the vitrinite-like maceral in the Lower Paleozoic shales: Insights from Raman spectroscopy of artificial pyrolysis residues

Vitrinite-like macerals (VLM) are ubiquitous in many pre-Devonian marine shales. The thermal maturity of these sediments, which are devoid of classical vitrinite, has been commonly evaluated using the reflectance of VLM as a substitute for vitrinite reflectance, but the molecular structure of VLM itself has seldom been examined. In this study, the immature VLM-rich Cambrian Alum shales from Scandinavia were selected and pyrolyzed at 300–550 ℃ to acquire a series of artificial pyrolysis samples with different ranks. The molecular structures and thermal evolution of VLM in natural and artificial shales were investigated by Raman spectroscopy. These Raman spectra and optical properties were compared with those of vitrinite, graptolite, and solid bitumen. The Raman spectra of VLM in natural samples of variable thermal maturities and immature samples altered by pyrolysis were generally comparable. The reduction of WD (D band position) and FWHM-G (full width at half maximum of the G band) and the increase of WG (G band position) and AD/AG (area ratio) in VLM spectra, which parallels the increasing thermal maturity of the samples, indicated an increased degree of aromatic conjugation and more structurally ordered carbon moieties. The increase in wavenumber difference between the D and G bands positions in Raman spectra (Raman band separation, RBS) demonstrated the gradual removal of oxygen-containing functional groups, the loss of aliphatic side chains, and the increased degree of aromatic ring condensation. In this way, with progressing maturity, the molecular structure of VLM gradually evolved from heterocyclic aromatic compounds and amorphous carbon structures at low maturity levels to structurally better-ordered, larger, aromatic fused-ring units characteristic of post-to-over mature samples. These molecular structures and their changes associated with thermal maturation were similar to those known from classical vitrinite. Aside from its reflectance, the thermal maturity of VLM-rich sediments could be assessed by Raman spectroscopy, notably through the RBS parameter of VLM Raman spectra, which closely correlated with VLM random reflectance throughout the reflectance interval between 0.5% and 5.5%.

The Significant Contribution of Polycyclic Aromatic Nitrogen Heterocycles to Light Absorption in the Winter North China Plain

By quantifying the absorption of black carbon (BC), brown carbon (BrC) and the lensing effect, we found that BrC dominates the total absorption at 450 nm, and the largest absorption contribution proportion of BrC could reach 78.3% during heavy pollution. The average absorption enhancement (Eabs) at 530 nm was only 1.38, indicating that BC is not coated well here. The average value of the absorption Ångstrom exponent (AAE) between 450 nm and 530 nm was 5.3, suggesting a high concentration of BrC in Wangdu. CHN+ was the greatest contributor to the light absorption of molecules detected in MSOC with a proportion of 12.2–22.4%, in which the polycyclic aromatic nitrogen heterocycles (PANHs) were the dominant compounds. The C6H5NO3 and its homologous series accounted for 3.0–11.3%, and the C15H9N and its homologous series, including one C16H11N and three C17H13N compounds, accounted for 5.1–12.3%. The absorption of these PANHs is comparable to that of nitro–aromatics, which should attract more attention to the impact of climate radiative forcing.

Synthesis, DFT, solvent effect and biological attributes of NLO active 4-bromo-2-((2-(2,4-Dinitrophenyl) hydrazono)methyl) phenol -Potent drug anti-brain cancer

The agrochemical and pharmaceutical sectors have relied heavily on heterocyclic aromatic compounds. This work comprises the synthesis and investigation of a hydrazine derivative using density functional theory (DFT). Vibrational wavenumbers have been calculated, scaled down, and compared with the experimental interpretations. The molecule's stability was evaluated utilising natural bond orbital (NBO) analysis. The standard prototype substance urea has been utilised as a reference for non-linear optical (NLO) behaviour analysis. Acetonitrile, an aprotic solvent, has a significant energy band gap of 3.122 eV and the least softness (0.329 eV), and DMSO (aprotic) has the least 2.635 eV spectral band gap. Solvents substantially influenced the comprehensive parameters and molecular reactivity of the molecule. Electron hole distribution analysis for the excitation states has been discussed. Topological studies such as ELF, LOL, and RDG (with solvents) analyses have been used to elucidate the bonding zones and weakest interactions and to access the energy density of electrons. Furthermore, it is observed that the polarity of solvents has a strong correlation with the electrical characteristics. The title compound, 4-bromo-2-((2-(2,4-Dinitrophenyl)hydrazono)methyl) phenol, adheres to Lipinski's rule of five, which implies that in practice using an oral dose of such chemicals shouldn't be harmful. The bio-activity of the composite was further assessed via molecular docking with cancer cell protein targets. Moreover, Ramachandran plots have been used to determine the stability of targeted proteins. Brain cancer cell proliferation protein (6ETJ) has the highest binding energy of -10.37 kcal/mol with the most non-covalent interactions.