Polycyclic Hydrocarbons Research Articles

Identification of local benzenoid aromaticity and global aromaticity of polycyclic aromatic hydrocarbons (PAHs) via the corresponding ring current effects in 1H NMR spectroscopy

Identification of local benzenoid aromaticity and global aromaticity of polycyclic aromatic hydrocarbons (PAHs) via the corresponding ring current effects in 1H NMR spectroscopy

Highly Selective On‐Surface Dehydrogenative Aromatization of n‐Hexyl to Phenyl Substituents

AbstractDehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl‐substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on‐surface thermal aromatization of n‐hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl‐substituted analogues under mild conditions. After depositing two representative precursor molecules, n‐hexyl‐substituted hexaphenylbenzene (HPB‐Hex) and bianthryl octacarboxylic tetraimide (BATI‐Hex), onto a pre‐heated Au(111) substrate, dehydroaromatization of the peripheral n‐hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C−C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl‐substituted hexabenzocoronene (HBC‐Ph) and bisanthene octacarboxylic tetraimides (BSTI‐Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond‐resolved non‐contact atomic force microscopy (nc‐AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n‐hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).

First data on concentrations and composition of polycyclic aromatic hydrocarbons in soil, bottom sediments and suspended matter of water throughout the whole Fatala River Basin (Republic of Guinea)

First data on concentrations and composition of polycyclic aromatic hydrocarbons in soil, bottom sediments and suspended matter of water throughout the whole Fatala River Basin (Republic of Guinea)

Characterization, source profiles and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in urban dust of 14 Chinese cities

ABSTRACT Data for 16 USEPA priority PAHs were collected in urban dust from 14 cities in China between 2008 and 2022, and concentration, profile composition, and human health risk were investigated. The mean concentration of PAHs was 6.60 mg kg−1, ranging from 2.88 mg kg−1 to 13.88 mg kg−1, and it was higher than other important cities in neighboring countries of China. Among different individual PAHs, mean fluoranthene (Flr) was dominant, accounting for 15.04%, and low molecular weight PAH (LMW) was almost a third of high molecular weight PAH (HMW). The results of PAH composition profiles suggested that the proportion of different rings of PAHs increased in order: 2-ring PAHs (4.40%)< 6-ring PAHs (15.73%)< 3-ring PAHs (17.77%)< 5-ring PAHs (22.54%)< 4-ring PAHs (39.56%). The results of the source appointment suggested that pyrogenic sources and mixed sources, particularly wood, grass, coal, and diesel combustion, were the main sources of PAHs in urban dust. The results of the health risk assessment illustrated that children were more vulnerable to PAHs, and ingestion was the dominant exposure pathway to PAHs (78.152%, 67.519%, 73.206%, and 72.957% of children, adolescents, adults, and the total lifetime cancer risk (TLCR)). PAH pollution in urban dust from different cities in China was a commonly existing phenomenon, but the mean and maximum of TLCR were acceptable according to the standard established by USEPA (10−4). Based on Monte Carlo simulations, body weight (BW) was the most important uncertain input in three age groups (60.75%-91.22% contribution).

The Effects of Phenanthrene on Electrical Activity in Ventricular Cardiomyocytes of Atlantic Cod (&lt;i&gt;Gadus morhua&lt;/i&gt;)

The production of oil on the Arctic shelf and its transport along the Northern Sea Route increase risks of pollution of the ecosystems in the Arctic seas with oil and oil products. Today, polyaromatic hydrocarbons are known as the most toxic oil components, and phenanthrene is predominant in terms of its concentration in oil and physiological effects. Phenanthrene affects the electrical activity of fish heart, but its effects are species-specific. At the same time, the effects of phenanthrene on cardiac function in Arctic fishes, including economically important commercial species, are studied not enough. This study examines the effects of phenanthrene on electrical activity and ionic currents in ventricular myocardium of Atlantic cod (Gadus morhua). The major ionic currents in cod myocardium were IKr, IK1, INa and ICa. Phenanthrene (1 μM) did not affect the duration of action potentials (APs) recorded in isolated cod ventricular cardiomyocytes using patch clamp method. Meanwhile, phenanthrene suppressed rapid delayed rectifier current IKr by 61.33 ± 3.94%, decreasing the repolarization reserve of the myocardium. Phenanthrene did not affect nor the level of resting membrane potential, not background inward rectifier current IK1. Also, application of phenanthrene decreased AP upstroke velocity in cod myocytes, which was due to the suppression of fast sodium current INa. Finally, phenanthrene slightly reduced the amplitude of calcium current ICa and accelerated its inactivation, which overall led to the decrease in ICa charge transfer. Thus, the effects of phenanthrene on cod myocardium at cellular level can be described as potentially proarrhythmic, which makes the populations of cod in Arctic seas vulnerable to pollution of the aquatic environment by oil components after oil spills due to technological disasters.

Toxicity, mutagenicity, and source identification of polycyclic aromatic hydrocarbons in ambient atmosphere and flue gas.

This study aimed to assess the characteristics of particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) from various stationary and mobile emission sources in Taiwan, with a focus on source apportionment and associated health risks. The northern power plant, equipped with bag filters operating at 150°C, had significantly lower FPM and CPM levels (0.44 and 0.13mg/m3, respectively) compared to the central and southern power plants, which used electrostatic precipitators operating at 250°C (FPM, 1.45-8.35mg/m3; CPM, 2.37-3.73mg/m3). Additionally, emissions from diesel vehicles under both idle and high-speed conditions exhibited higher FPM levels (3.46-4.67mg/m3) than gasoline vehicles (0.19-0.40mg/m3). In terms of PAH toxicity, diesel vehicle emissions had significantly higher BaP-TEQ (87.3ng/m3) and BaP-MEQ (25.9ng/m3) levels compared to power plants (BaP-TEQ, 5.49ng/m3; BaP-MEQ, 2.65ng/m3). The highest ambient concentrations of PM2.5, BaP-TEQ, and BaP-MEQ were recorded at traffic sites, with values of 48 ± 36µg/m3, 0.29ng/m3, and 0.11ng/m3, respectively. Differences in PAH distributions between stationary and mobile sources were influenced by factors such as pollution control technologies, combustion temperatures, and fuel types. Diesel vehicle emissions were dominated by benzo[g,h,i]perylene (BghiP), indeno[1,2,3-cd]pyrene (IND), benzo[a]pyrene (BaP), and benzo[b]fluoranthene (BbF) under idle conditions, while phenanthrene (PA), pyrene (Pyr), and BghiP were prevalent under high-speed conditions. Source apportionment conducted using principal component analysis (PCA) and positive matrix factorization (PMF) identified diesel and gasoline vehicles as the dominant contributors to atmospheric PAHs in Taiwan, accounting for 38% of the total, followed by coal-fired power plants at 35%. The highest lifetime excess cancer risk (ECR) of 2.5 × 10⁻5 was observed in traffic-dense areas, emphasizing the public health implications of vehicle emissions. The study adds credibility to the source apportionment findings, and the health risk analysis highlights variations across different regions, including traffic, urban, rural, and background zones.

DFT and Model Hamiltonian Study of Optoelectronic Properties of Some Low-Symmetry Graphene Quantum Dots.

We have studied the electronic and optical properties of three low-symmetry graphene quantum dots (GQDs), with point-group symmetries C2v and C2h. For the calculations of linear optical absorption spectra, we employed both first-principles time-dependent density-functional theory (TDDFT) and the electron-correlated Pariser-Parr-Pople (PPP) model coupled with the configuration-interaction (CI) approach. In the PPP-CI approach, calculations were performed using both screened and standard parameters, along with efficiently incorporating electron correlation effects using multireference singles-doubles CI for both ground and excited states. We assume that the GQDs are saturated by hydrogen atoms at the edges, making them effectively polycyclic aromatic hydrocarbons (PAHs) dibenzo[bc,ef]coronene (also known as benzo(1,14)bisanthene, C30H14) and two isomeric compounds, dinaphtho[8,1,2abc;2',1',8'klm]coronene and dinaphtho[8,1,2abc;2',1',8'jkl]coronene with the chemical formula C36H16. The two isomers have different point group symmetries; therefore, this study will also help us understand the influence of symmetry on the optical properties. A common feature of the absorption spectra of the three GQDs is that the first peak representing the optical gap is of low to moderate intensity, while the intense peaks appear at higher energies. For each GQD, PPP model calculations performed with the screened parameters agree well with the experimental results of the corresponding PAH and also with the TDDFT calculations. To further quantify the influence of electron-correlation effects, we also computed the singlet-triplet gap (spin gap) of the three GQDs, and we found them to be significant.

Battle of the CH motions: aliphatic vs. aromatic contributions to astronomical PAH emission and exploration of the aliphatic, aromatic, and ethynyl CH stretches

Abstract Strong anharmonic coupling between vibrational states in polycyclic aromatic hydrocarbons (PAH) produces highly mixed vibrational transitions that challenge the current understanding of the nature of the astronomical mid-infrared PAH emission bands. Traditionally, PAH emission bands have been characterized as either aromatic or aliphatic, and this assignment is used to determine the fraction of aliphatic carbon in astronomical sources. In reality, each of the transitions previously utilized for such an attribution is highly mixed with contributions from both aliphatic and aromatic CH motions as well as non-CH motions such as CC stretches. High-resolution gas-phase IR absorption measurements of the spectra of the aromatic molecules indene and 2-ethynyltoluene at the Canadian Light Source combined with high-level anharmonic quantum chemical computations reveal the complex nature of these transitions, implying that the use of these features as a marker for the aliphatic fraction in astronomical sources is not uniquely true or actually predictive. Further, the presence of aliphatic, aromatic, and ethynyl CH groups in 2-ethynyltoluene provides an internally consistent opportunity to simultaneously study the spectroscopy of all three astronomically important groups. Finally, this study makes an explicit connection between fundamental quantum mechanical principles and macroscopic astronomical chemical physics, an important link necessary to untangle the lifecycle of stellar and planetary systems.

Detectability of polycyclic aromatic hydrocarbons in the atmosphere of WASP-6 b with JWST NIRSpec PRISM

Abstract Polycyclic Aromatic Hydrocarbons (PAHs) have been detected throughout the universe where they play essential roles in the evolution of their environments. For example, they are believed to affect atmospheric loss rates of close-in planets and might contribute to the pre-biotic chemistry and emergence of life. Despite their importance, the study of PAHs in exoplanet atmospheres has been limited. We aim to evaluate the possibility of detecting PAHs on exoplanets considering future observations using JWST’s NIRSpec PRISM mode. The hot Saturn WASP-6 b shows properties that are consistent with a potential PAH presence and is thus used as a case study for this work. Here, we compare the likelihoods of various synthetic haze species and their combinations with the influence of PAHs on the transmission spectrum of WASP-6 b. This is possible by applying the atmospheric retrieval code petitRADTRANS to a collection of data from previous observations. Subsequently, by exploring synthetic, single transit JWST spectra of this planet that include PAHs, we assess if these molecules can be detected in the near future. Previous observations support the presence of cloud/haze species in the spectrum of WASP-6 b. While this may include PAHs, the current data do not confirm their existence unambiguously. Our research suggests that utilizing the JWST for future observations could lead to a notable advancement in the study of PAHs. Employing this telescope, we find that a PAH abundance of approximately 0.1percnt of the ISM value could be robustly detectable.

Characteristics, prediction, and risk assessment of phthalates, organophosphate esters, and polycyclic aromatic hydrocarbons in vegetables from plastic greenhouses of Northeast China.

We investigated the contaminations of phthalates (PAEs), organophosphate esters (OPEs), and polycyclic aromatic hydrocarbons (PAHs) in the vegetables and their corresponding soils from 26 plastic greenhouses of Northeast China. PAEs, OPEs, and PAHs in the edible portion of vegetables were in the range of 2620-21800, 115-852, and 32.4-602 ng/g, while the levels of these chemicals in the greenhouse soils were 5770-18800, 196-935, and 109-1600 ng/g, respectively. PAEs are the main organic pollutants in greenhouses, which were 1-2 orders of magnitude higher than that of OPEs and PAHs. Leafy vegetables showed the highest contamination level, which is ∼1-3 times that of root and fruit vegetables. Bioaccumulation factors (BAFs) of chemicals are significantly negatively correlated with their physicochemical properties, e.g., octanol-water partition coefficient and organic carbon partition coefficient. The partition-limited model can accurately predict the contamination level of greenhouse vegetables to a certain extent based on the chemical's concentration in the corresponding soil. We assessed the hazard quotients of target compounds through daily intake of greenhouse vegetables, and found a low risk for di(2-ethylhexyl) phthalate. This research emphasized the potential dietary exposure risks caused by greenhouse leafy vegetables, and proposed a method for evaluating the risk of greenhouse vegetables through soil monitoring.

Seasonality, sources apportionment, human health risks assessments, and potential implications on the atmospheric chemistry of polycyclic aromatic hydrocarbons in size-segregated aerosols from a Romanian metropolitan area.

Urbanization and industrialization are important transformations shaping the current statement of the society, enhancing significantly the combustion emissions which are threatening the global climate system, air quality, and human health. These emissions contain polycyclic aromatic hydrocarbons (PAHs) which are well known for their high toxicity. The present study is the first assessing the seasonal variation of 17 PAHs in size segregated fractions of atmospheric aerosol particles from a Romanian metropolitan area. In addition to sources apportionment and health risks, the potential role of PAHs on the atmospheric chemistry in the area was also addressed. Higher PAHs concentrations were determined in winter season, the highest values being quantified for benzo[b]fluoranthene, benzo[a]pyrene, and indeno[1,2,3-cd]pyrene. Each analyzed PAH exhibited a dominant peak in the accumulation mode (0.1-1.0 μm), with maxima at 381 nm. Gasoline combustion was identified as a significant contributor to the PAHs levels in the atmospheric aerosols from the area. Biomass-burning contributions were highlighted during the winter and autumn seasons. The positive matrix factorization (PMF) model apportioned four PAHs sources, as follows: vehicular (31%), mixed combustion (33%), biomass and wood burning (19%), and coal and natural gas combustion (18%) sources. Concentration-weighted trajectory (CWT) analysis method revealed clear contributions to PAHs abundances from local and regional air masses. Alveolar region of adults seems to have the highest susceptibility for PAHs deposition. Values exceeding acceptable limits for carcinogenic risk throughout the year are associated with benzo[a]pyrene, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, benzo[a]anthracene etc. The present study can be considered as a reference in the region in order measures of mitigation and control for PAHs emission sources to be introduced.

Synthesis of Regular Ladder-Type Fluorenylidene-Xanthene Oligomers via Nucleophilic Aromatic Substitution Reaction.

Fluorenylidene-xanthene and related polycyclic systems are typical examples of bistricyclic aromatic enes (BAEs); however, polycyclic systems of fluorenylidene-xanthene are relatively scarce. Here we synthesized a series of novel ladder-type polycyclic systems containing fluorenylidene-xanthene units, differing from the classic Barton's two-fold extrusion reaction. In the new synthetic scheme, the very popular Suzuki reaction was first used to couple the corresponding precursors, then a catalyst-free nucleophilic aromatic substitution reaction between Ar-F and Ar-OH groups in the backbone afforded ladder-type O-heteroarenes. Moreover, the new synthetic strategy is also suitable for the synthesis of other heterocyclic and polycyclic aromatic hydrocarbons. Some of these products showed reversible mechanochromism properties.

Air pollution and skin aging

Air pollution is a leading environmental health risk worldwide, with detrimental effects not only on human health but also on skin aging. This review explores the link between air pollution and skin aging, focusing on the harmful effects of particulate matter (PM) and other pollutants such as polycyclic aromatic hydrocarbons (PAHs), nitrogen oxides (NO2), and ozone (O3). These pollutants penetrate the skin, inducing oxidative stress and inflammation, which accelerates the degradation of collagen and elastin in the extracellular matrix. This contributes to premature aging, wrinkles, hyperpigmentation, and inflammatory skin conditions. The smallest fractions of PM, particularly PM2.5, are the most harmful, causing significant cellular damage. Long-term exposure to these pollutants also disrupts the skin's microbiome, leading to dysbiosis and further weakening the skin's protective barrier. Current therapeutic strategies focus on protecting the skin using antioxidants, such as Vitamin C and Vitamin E, as well as probiotics and moisturizers that support the skin's natural defenses. Sunscreens also play a vital role in protecting the skin from UV-induced oxidative stress, further mitigating pollution-related damage. This review highlights the importance of developing comprehensive skincare regimens that target both pollution-induced oxidative stress and the maintenance of a healthy skin barrier. It also emphasizes the need for further research into personalized approaches to counteract the aging effects of air pollution on the skin.

Screening of municipal effluents with the peroxidase toxicity assay

AbstractThe peroxidase (Per) reaction is a quick and inexpensive biosensor for the screening of environmental contaminants and wastewaters. The purpose of this study was to screen various municipal wastewaters before and after 7 different types of treatment processes using this sensor to identify potential sites under stress by urban pollution. The following wastewater samples before (influent) and after the commonly applied treatments (effluent) were tested using the Per activity test: advanced biofiltration, biofiltration, aerated lagoons, secondary aeration sludge, trickling filter, secondary membrane filtration, and primary. The influents and effluents were collected for 3 days and concentrated to 500 X on a reverse-phase (C18) extraction cartridge. The ethanol extracts were examined for dissolved organic carbon, plastic-like materials, polyaromatic hydrocarbons and polystyrene nanoplastics. The samples were then tested using the Per reaction alone and in the presence of DNA to detect DNA binding agents. The results show that population size tended to increase Per activity and 60% of the effluents decreased Per activity leading to H2O2 persistence and toxicity. More advanced treatments (biofiltration, membrane biofiltration, secondary aeration) produced stronger changes from the corresponding untreated influents corroborating their performance in reducing toxicity. The addition of DNA during the Per reaction revealed that population size had no influence and that 60% of treated effluents restored Per activity suggesting release of genotoxic compounds in the aquatic environment from treated wastewaters. The toxic implications of the continuous release of wastewaters in aquatic ecosystems are discussed in the light of emerging contaminants such as nanoplastics.

Inhibition of Polycyclic Aromatic Hydrocarbons Formation During Supercritical Water Gasification of Sewage Sludge by H2O2 Combined with Catalyst

This work evaluated the alterations in the levels and types of polycyclic aromatic hydrocarbons (PAHs) within both liquid and solid products throughout the process of the catalytic supercritical water gasification of dewatered sewage sludge to examine the catalytic effect of various catalysts and the inhibit reaction pathways. The addition of Ni, NaOH, Na2CO3, H2O2, and KMnO4 reduced the concentrations of PAHs, with Ni and H2O2 showing the best performance. The concentrations of PAHs, especially higher-molecular-weight compounds in the residues, decreased sharply as the H2O2 amount increased. At a 10 wt% H2O2 addition, the levels of PAHs in the liquid and solid products were reduced by 91% and 88%, respectively. High-ring PAHs were not detected in the residues as the H2O2 amount increased to an 8 wt%. H2O2 addition evidently inhibits PAH formation by promoting the ring-opening reactions of initial aromatic compounds in raw sludge and inhibiting the polymerization of open-chain intermediate products. The addition of NaOH + H2O2 or Ni + H2O2 as combined catalysts significantly lowered PAH concentrations while increasing the H2 yield. The addition of 5 wt% Ni + H2O2 reduced PAH concentrations in the liquid and solid residues by 70% and 44%, respectively, while the H2 yield escalated from 0.13 mol/kg OM to 3.88 mol/kg OM. Possible mechanisms associated with the reaction pathways of these combined catalysts are proposed.

Exploring the possibility of polycyclic aromatic hydrocarbons and fulleranes as the carrier of the 21 micron emission feature

IntroductionThe 21 μm emission feature discovered in a small sample of carbon-rich protoplanetary nebulae has remained unidentified for over 30 years. A dozen of different molecular species (both organics and inorganics) have been proposed as the carrier candidates of this important feature, among which polycyclic aromatic hydrocarbons (PAHs) and fulleranes (hydrogenated fullerenes) have yet to be sufficiently examined.MethodIn this study, we attempt to fit the 21 μm features in observed spectra of the above-mentioned astronomical sources via theoretically simulated spectra of various PAHs and fulleranes, aiming to investigate whether the two hydrocarbon families can reproduce the 21 μm feature.Results and DiscussionBased on the fitting outcomes we conclude that fulleranes can provide a more plausible explanation for the origin of 21 μm feature than PAHs.

Unraveling the enigma: chronic kidney disease of unknown etiology and its causative factors with a specific focus ondissolved organic compounds in groundwater-reviews and future prospects.

Chronic kidney disease is globally recognized as a highly impactful non-communicable disease. The inability of early identification contributes to its high mortality rate and financial burden on affected individuals. Chronic kidney disease of uncertain etiology (CKDu) constitutes a significant global public health concern. This condition does not arise from traditional risk factors such as diabetes, hypertension, or glomerulonephritis. More than 150 articles were analysed to understand risk factors of CKDu. This study aimed to investigate the potential association between dissolved organic compounds, such as Polycyclic Aromatic Hydrocarbons and Humic Acid, and the incidence of CKDu. Through a comprehensive literature review, we identified CKDu clusters worldwide, including notable nephropathies, and explored their potential links with organic compounds. Our analysis revealed that organic compounds can leach from sediments and low-rank lignite deposits into groundwater, subsequently contaminating water supplies and food. These compounds have been implicated in the development of diabetes and increased heavy metal mobility, both of which are risk factors for kidney disease. Our findings suggest that exposure to organic compounds may contribute to the etiology of CKDu, underscoring the need for regular monitoring and establishment of baseline and threshold values in water and soil. We also emphasize the importance of analyzing organic compounds in groundwater in CKDu hotspots and establishing distinct registries for CKD and CKDu implementation.

Recent Advances in the Cascade Cyclization of Alkyne Units for the Construction of Benzofluorenes

AbstractBenzofluorenes are an important class of polycyclic aromatic hydrocarbons (PAHs), which are widely used in materials science for light‐sensitive electronic components. In addition, the benzofluorene skeleton also serves as a key structural unit in various natural products. Therefore, the development of synthetic strategies for the construction of benzofluorenes has been a prominent research topic in synthetic chemistry. Over the past few decades, numerous efforts have been made for the construction of benzofluorenes via cascade cyclization of alkyne units. This review aims to summarize recent advances in the cascade cyclization of alkyne units for the construction of Based on the different reaction mechanisms underlying these transformations, this review can be divided into four categories: (1) thermal‐induced cascade cyclization of alkyne units for the construction of benzofluorenes, (2) metal‐catalyzed cascade cyclization of alkyne units for the construction of benzofluorenes, (3) acid‐promoted/catalyzed cyclization of alkyne units for the construction of benzofluorenes, and (4) base‐promoted cascade cyclization of alkyne units for the construction of benzofluorenes.

Recent Findings on the Pollution Levels in the Romanian Black Sea Ecosystem: Implications for Achieving Good Environmental Status (GES) Under the Marine Strategy Framework Directive (Directive 2008/56/EC)

This study provides a comprehensive evaluation of contamination levels in the Romanian Black Sea within the framework of the Marine Strategy Framework Directive (MSFD). Over the course of five oceanographic expeditions between 2020 and 2022, data were gathered from 70 stations in transitional, coastal, shelf, and offshore waters of the Black Sea. Analyses were conducted on water, sediment, and biota samples for key contaminants: heavy metals (HMs), polycyclic aromatic hydrocarbons (PAHs), and persistent organic pollutants (POPs) such as organochlorinated pesticides (OCPs) and polychlorinated biphenyls (PCBs). The assessment identified contamination hotspots near riverine inputs, urban runoff, harbor activities, and industrial discharges. Offshore waters also showed measurable pollutant levels, likely from diffuse sources and atmospheric deposition. The key findings reveal the widespread contamination of HMs, PAHs, and POPs across the Romanian Black Sea, with concentrations in certain areas exceeding acceptable environmental thresholds, highlighting ongoing challenges for regional pollution management. PAHs were prevalent in both nearshore and offshore regions, while OCPs and PCBs were detected across various matrices, with significant concentrations observed in water and biota samples. The study emphasizes the importance of integrated assessments within the MSFD framework, suggesting that future evaluations should complement the “one out-all out” (OOAO) approach with multi-metric tools, to enhance the robustness of pollution status reporting. Despite improvements in some areas, contamination remains a critical challenge, requiring strengthened regulations, improved waste management, and increased regional cooperation to mitigate the ongoing risks to marine ecosystems. The findings provide valuable data for the upcoming national MSFD assessment cycle (2018–2023) and highlight the need for sustained monitoring and coordinated efforts to ensure long-term marine sustainability.

Highly Selective On-Surface Dehydrogenative Aromatization of n-Hexyl to Phenyl Substituents.

Dehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl-substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on-surface thermal aromatization of n-hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl-substituted analogues under mild conditions. After depositing two representative precursor molecules, n-hexyl-substituted hexaphenylbenzene (HPB-Hex) and bianthryl octacarboxylic tetraimide (BATI-Hex), onto a pre-heated Au(111) substrate, dehydroaromatization of the peripheral n-hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C-C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl-substituted hexabenzocoronene (HBC-Ph) and bisanthene octacarboxylic tetraimides (BSTI-Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond-resolved non-contact atomic force microscopy (nc-AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n-hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).