Reduction of Thorium Tris(amido)arene Complexes: Reversible Double and Single C-C Couplings.

The reduction chemistry of thorium complexes is less explored compared to that of their uranium counterparts. Here, we report the synthesis, characterization, and reduction chemistry of two thorium(IV) complexes, (AdTPBN3)ThCl (1) and (DtbpTPBN3)ThCl(THF) (4) [RTPBN3 = 1,3,5-[2-(RN)C6H4]3C6H3; R = 1-adamantyl (Ad) or 3,5-di-tert-butylphenyl (Dtbp); THF = tetrahydrofuran], supported by tripodal tris(amido)arene ligands with different N-substituents. Reduction of 1 with excessive potassium in n-pentane yielded a double C-C coupling product, [(AdTPBN3)ThK(Et2O)2]2 (3), featuring a unique tetraanionic tricyclic core. On the other hand, reduction of 4 with 1 equiv of KC8 in hexanes/1,2-dimethoxyethane (DME) afforded a single C-C coupling product, [(DtbpTPBN3)Th(DME)]2 (5), with a dianionic bis(cyclohexadienyl) core. The solid- and solution-state structures of dinuclear thorium(IV) complexes 3 and 5 were established by X-ray crystallography and NMR spectroscopy. In addition, reactivity studies show that 3 and 5 can behave as thorium(II) and thorium(III) synthons to reduce organic halides. For instance, 3 and 5 are able to reduce 4 and 2 equiv of benzyl chloride, respectively, to regenerate 1 and 4 with concomitant formation of dibenzyl. Reversible C-C couplings under redox conditions provide an alternative approach to exploiting the potential of thorium arene complexes in redox chemistry.

Phthalate acid esters: A review of aquatic environmental occurrence and their interactions with plants.

The increasing use of phthalate acid esters (PAEs) in various applications has inevitably led to their widespread presence in the aquatic environment. This presents a considerable threat to plants. However, the interactions between PAEs and plants in the aquatic environment have not yet been comprehensively reviewed. In this review, the properties, occurrence, uptake, transformation, and toxic effects of PAEs on plants in the aquatic environment are summarized. PAEs have been prevalently detected in the aquatic environment, including surface water, groundwater, seawater, and sediment, with concentrations ranging from the ng/L or ng/kg to the mg/L or mg/kg range. PAEs in the aquatic environment can be uptake, translocated, and metabolized by plants. Exposure to PAEs induces multiple adverse effects in aquatic plants, including growth perturbation, structural damage, disruption of photosynthesis, oxidative damage, and potential genotoxicity. High-throughput omics techniques further reveal the underlying toxicity molecular mechanisms of how PAEs disrupt plants on the transcription, protein, and metabolism levels. Finally, this review proposes that future studies should evaluate the interactions between plants and PAEs with a focus on long-term exposure to environmental PAE concentrations, the effects of PAE alternatives, and human health risks via the intake of plant-based foods.

The hidden diet: Synthetic antioxidants in packaged food and their impact on human exposure and health.

Synthetic antioxidants (AOs) are commonly used in everyday items and industrial products to inhibit oxidative deterioration. However, the presence of AOs in food packaging and packaged foods has not been thoroughly documented. Moreover, studies on human exposure to AOs through skin contact with packaging or ingesting packaged foods are limited. In this study, we analyzed twenty-three AOs-including synthetic phenolic antioxidants (SPAs) and organophosphite antioxidants (OPAs)-along with six transformation products in various food samples and their packaging materials. We found AOs in food products at concentrations ranging from 1.30 × 103 to 1.77 × 105 ng/g, which exceeded the levels in both outer packaging (6.05 × 102-3.07 × 104 ng/g) and inner packaging (2.27 × 102-1.09 × 105 ng/g). The most common AOs detected in foodstuffs were tris(2,4-di-tert-butylphenyl) phosphate (AO168O), butylated hydroxytoluene (BHT), and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (AO1076), together constituting 95.7 % of the total AOs found. Our preliminary exposure assessment revealed that dietary exposure-estimated at a median of 2.55 × 104 ng/kg body weight/day for children and 1.24 × 104 ng/kg body weight/day for adults-is a more significant exposure route than dermal contact with packaging. Notably, four AOs were identified in food for the first time, with BHT making up 76.8 % and 67.6 % of the total BHT intake for children and adults, respectively. These findings suggest that food consumption is a significant source of BHT exposure. The estimated daily intakes of AOs via consumption of foodstuffs were compared with the recommended acceptable daily intake to assess the risks. This systematic investigation into AOs contributes to understanding potential exposure and health risks associated with AOs in packaged foods. It emphasizes the need for further evaluation of human exposure to these substances.

AhR Agonistic Components in Urban Particulate Matter Regulate Astrocytic Activation and Function.

Exposure to atmospheric particulate matter (PM) has been found to accelerate the onset of neurological disorders via the induction of detrimental neuroinflammatory responses. To reveal how astrocytes respond to urban atmospheric PM stimulation, a commercially available standard reference material (SRM1648a) was tested in this study on the activation of rat cortical astrocytes. The results showed that SRM1648a stimulation induced both A1 and A2 phenotypes in astrocytes, as characterized by the exposure concentration-dependent increases in Fkbp5, Sphk1, S100a10, and Il6 mRNA levels. Studying the functional alterations of astrocytes indicated that the neurotrophic factors of Gdnf and Ngf were transcriptionally upregulated due to astrocytic A2-type activation. SRM1648a also promoted autonomous motility of astrocytes and elevated the expressions of chemokines. The aryl hydrocarbon receptor (AhR) agonistic components, such as polycyclic aromatic hydrocarbons (PAHs), were recognized to greatly contribute to SRM1648a-induced effects on astrocytes, which was confirmed by the attenuation of PM-disturbed astrocytic effects via AhR blockage. This study, for the first time, uncovered the direct regulation of urban atmospheric PM on astrocytic activation and function and traced the containing bioactive components (e.g., PAHs) with AhR agonistic activity. The findings provided new knowledge on understanding the ambiguous neurological disturbance from ambient fine PM pollution.

Synthetic Antioxidants as Contaminants of Emerging Concern in Indoor Environments: Knowns and Unknowns.

Synthetic antioxidants, including synthetic phenolic antioxidants (SPAs), amine antioxidants (AAs), and organophosphite antioxidants (OPAs), are essential additives for preventing oxidative aging in various industrial and consumer products. Increasing attention has been paid to the environmental contamination caused by these chemicals, but our understanding of synthetic antioxidants is generally limited compared to other emerging contaminants such as plasticizers and flame retardants. Many people spend a significant portion (normally greater than 80%) of their time indoors, meaning that they experience widespread and persistent exposure to indoor contaminants. Thus, this Perspective focuses on the problem of synthetic antioxidants as indoor environmental contaminants. The wide application of antioxidants in commercial products and their demonstrated toxicity make them an important family of indoor contaminants of emerging concern. However, significant knowledge gaps still need to be bridged: novel synthetic antioxidants and their related transformation products need to be identified in indoor environments, different dust sampling strategies should be employed to evaluate human exposure to these contaminants, geographic scope and sampling scope of research on indoor contamination should be broadened, and the partition coefficients of synthetic antioxidants among different media need to be investigated.

Two-Electron Oxidations at a Single Cerium Center.

Two-electron oxidations are ubiquitous and play a key role in the synthesis and catalysis. For transition metals and actinides, two-electron oxidation often takes place at a single-metal site. However, redox reactions at rare-earth metals have been limited to one-electron processes due to the lack of accessible oxidation states. Despite recent advancements in nontraditional oxidation state chemistry, the low stability of low-valent compounds and large disparity among different oxidation states prevented the implementation of two-electron processes at a single rare-earth metal center. Here we report two-electron oxidations at a cerium(II) center to yield cerium(IV) terminal oxo and imido complexes. A series of cerium(II-IV) complexes supported by a tripodal tris(amido)arene ligand were synthesized and characterized. Experimental and theoretical studies revealed that the cerium(II) complex is best described as a 4f2 ion stabilized by δ-backdonation to the anchoring arene, while the cerium(IV) oxo and imido complexes exhibit multiple bonding characters. The accomplishment of two-electron oxidations at a single cerium center brings a new facet to molecular rare-earth metal chemistry.

Accessing five oxidation states of uranium in a retained ligand framework.

Understanding and exploiting the redox properties of uranium is of great importance because uranium has a wide range of possible oxidation states and holds great potential for small molecule activation and catalysis. However, it remains challenging to stabilise both low and high-valent uranium ions in a preserved ligand environment. Herein we report the synthesis and characterisation of a series of uranium(II-VI) complexes supported by a tripodal tris(amido)arene ligand. In addition, one- or two-electron redox transformations could be achieved with these compounds. Moreover, combined experimental and theoretical studies unveiled that the ambiphilic uranium-arene interactions are the key to balance the stabilisation of low and high-valent uranium, with the anchoring arene acting as a δ acceptor or a π donor. Our results reinforce the design strategy to incorporate metal-arene interactions in stabilising multiple oxidation states, and open up new avenues to explore the redox chemistry of uranium.

Occurrence, Fate, Human Exposure, and Toxicity of Commercial Photoinitiators.

Photoinitiators (PIs) are a family of anthropogenic chemicals used in polymerization systems that generate active substances to initiate polymerization reactions under certain radiations. Although polymerization is considered a green method, its wide application in various commercial products, such as UV-curable inks, paints, and varnishes, has led to ubiquitous environmental issues caused by PIs. In this study, we present an overview of the current knowledge on the environmental occurrence, human exposure, and toxicity of PIs and provide suggestions for future research based on numerous available studies. The residual concentrations of PIs in commercial products, such as food packaging materials, are at microgram per gram levels. The migration of PIs from food packaging materials to foodstuffs has been confirmed by more than 100 reports of food contamination caused by PIs. Furthermore, more than 20 PIs have been detected in water, sediment, sewage sludge, and indoor dust collected from Asia, the United States, and Europe. Human internal exposure was also confirmed by the detection of PIs in serum. In addition, PIs were present in human breast milk, indicating that breastfeeding is an exposure pathway for infants. Among the most available studies, benzophenone is the dominant congener detected in the environment and humans. Toxicity studies of PIs reveal multiple toxic end points, such as carcinogenicity and endocrine-disrupting effects. Future investigations should focus on synergistic/antagonistic toxicity effects caused by PIs coexposure and metabolism/transformation pathways of newly identified PIs. Furthermore, future research should aim to develop "greener" PIs with high efficiency, low migration, and low toxicity.

3-tert-Butyl-4-hydroxyanisole perturbs renal lipid metabolism in vitro by targeting androgen receptor-regulated de novo lipogenesis.

The widespread usage of 3-tert-butyl-4-hydroxyanisole (3-BHA) as an anthropogenic antioxidant has caused considerable environmental contamination and frequent detection in diverse human-derived samples. 3-BHA can promote adipogenesis and impair hepatic lipid metabolism, while its effects on renal lipid homeostasis remain to be uncertain. Herein, using the human kidney 2 (HK-2) cell experiments, 3-BHA was found to cause a significant reduction in lipid accumulation of the HK-2 cells in both exposure concentration- and duration-dependent manners. Exposure to 3-BHA lowered the transcriptional expressions of sterol regulatory element-binding protein 1 (SREBP1) and acetyl-CoA carboxylase (ACC), as well as ACC activity, indicating the inhibition in the process of de novo lipogenesis in HK-2 cells. On this basis, the mechanism study suggested that the reduced glucose absorption and accelerated glycolysis were concomitantly involved. The antagonism of 3-BHA on the transactivation of androgen receptor (AR) contributed to the lowered de novo lipogenesis and the consequent intracellular lipid reduction. The metabolomics data further confirmed the imbalance of lipid homeostasis and dysregulation of de novo lipogenesis. The new findings on the impaired renal lipid metabolism induced by 3-BHA warranted proper care about the usage of this chemical as a food additive.

The perturbation of parabens on the neuroendocrine system in zebrafish larvae.

Parabens, as the synthetic preservatives, have caused universal environmental contamination and human exposure. Whether parabens could disturb neuroendocrine system was still ambiguous. In this study, the effects of four commonly-used parabens, i.e. methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP) and butyl paraben (BuP), were tested on the neuroendocrine system of zebrafish larvae by investigating the swimming behavior, the related hormones and biomarkers in the hypothalamic-pituitary-interrenal (HPI) axis. The results showed that all test chemicals significantly reduced the swimming distance and mean velocity of zebrafish larvae. The adrenocorticotropic hormone (ACTH) levels in zebrafish larvae were significantly increased, while the cortisol levels were obviously decreased by paraben exposure. The transcriptional analysis showed that the expressions of the target genes including gr, mr and crhr2 in the HPI axis were mostly down-regulated. The exploration of the initial molecular event showed that parabens could bind with the glucocorticoid receptor (GR) and trigger its transactivation, according to MDA-kb2 luciferase assay and molecular docking analysis. The interaction of parabens with the GR included the hydrogen bond and hydrophobic interaction. The findings herein revealed the potential deleterious effects of parabens on the neuroendocrine system of zebrafish larvae, thus accumulating the in vivo toxicological data on this kind of food preservatives.

Studying paraben-induced estrogen receptor- and steroid hormone-related endocrine disruption effects via multi-level approaches.

Increasing concerns have been raised on the health risks of parabens in the regard of their widespread applications and potential endocrine disrupting activities. In this study, four typical parabens, including methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP), and butyl paraben (BuP) were systematically investigated for their estrogen receptor- and steroid hormone-related endocrine disruptions using multi-level approaches. Paraben exposure promoted the proliferation of MCF-7 cells, increased the luciferase activity in MVLN cells, and induced the vitellogenin (vtg) expression in zebrafish larvae, showing the typical estrogenic effects. The in vitro protein assays further revealed that PrP and BuP could bind with two isoforms of estrogen receptors (ERs). The estrogenic activities of parabens were predicted to be positively correlated with their chemical structure complexity by using molecular docking analysis. Furthermore, the synthesis and secretion of estradiol (E2) and testosterone (T) were significantly disturbed in H295R cells and zebrafish larvae, which could be regulated by paraben-induced transcriptional disturbance in both in vitro steroidogenesis and in vivo hypothalamic-pituitary-gonadal (HPG) axis. Parabens could disturb the endocrine system by activating the ERs and disrupting the steroid hormone synthesis and secretion, suggesting their potential deleterious risks to the environment and human health.

Trivalent rare-earth metal cyclic (alkyl)(amino)carbene complexes.

Coordination chemistry of cyclic (alkyl)(amino)carbene (CAAC) ligands has blossomed in recent years, exemplified by their strong σ-donating and π-accepting ability. However, trivalent rare-earth metal CAAC complexes remain elusive. By using M(CH2SiMe3)3(THF)2 (M = Sc, Y and Lu) as precursors, we synthesized mono CAAC coordinated rare-earth metal trisalkyl complexes, (RCAAC)M(CH2SiMe3)3 (R = Me and Et, M = Sc, Y and Lu). In addition, when MI3(Et2O)n (M = Y and Yb) were employed as metal precursors, bis(CAAC)-stabilized rare-earth metal triiodide complexes (MeCAAC)2MI3 (M = Y and Yb) could be obtained. All new compounds were characterized by X-ray crystallography, elemental analysis and NMR spectroscopy. Density functional theory calculations were conducted for these rare-earth metal CAAC complexes to gain insight into their electronic structures and bonding interactions. The bonding analysis unveils that the CAAC ligands act as σ donors to trivalent rare-earth metal ions and may be involved in π-bonding upon reduction.

Dualistic effects of bisphenol A on growth, photosynthetic and oxidative stress of duckweed (Lemna minor).

In this study, we exposed duckweed (Lemna minor), a floating freshwater plant, to BPA at different concentrations (0, 1, 5, 20, and 50 mg/L) for 7 days so as to investigate the effects of BPA on its growth, photosynthesis, antioxidant system, and osmotic substances. It was found that BPA had the acute toxic effects of "low promotion and high inhibition" on growth and photosynthesis. Specifically, BPA at a low concentration (5 mg/L) significantly promoted the plant growth and improved the concentration of photosynthetic pigments (chlorophyll a, b, and total Chl ) of L. minor. However, BPA at a high concentration (50 mg/L) significantly inhibited the plant growth, the Chl content, and the maximal photochemical efficiency (Fv/Fm). Furthermore, BPA with high concentration (50 mg/L) induced ROS accumulation and increased the activities of antioxidant enzymes (SOD, CAT, POD, APX, and GR) and the contents of antioxidant substances (GSH, proline, and T-AOC), which indicated that L. minor might tolerate BPA toxicity by activating an antioxidant defense system. The correlation analysis revealed that the fresh weight of L. minor was significantly and positively correlated with photosynthesis and the contents of soluble protein and sugar, while it was negatively correlated with the content of H2O2. Totally, these results showed that BPA at different concentrations had dualistic effects on the growth of L. minor, which was attributed to the alterations of photosynthesis, oxidative stress, and osmotic regulation systems and provided a novel insight for studying the effects of BPA on aquatic plant physiology.

Perfluorinated Iodine Alkanes Promoted Neural Differentiation of mESCs by Targeting miRNA-34a-5p in Notch-Hes Signaling.

The neurodevelopmental process is highly vulnerable to environmental stress from exposure to endocrine-disrupting chemicals. Perfluorinated iodine alkanes (PFIs) possess estrogenic activities, while their potential neurodevelopmental toxicity remains blurry. In the present study, the effects of two PFIs, including dodecafluoro-1,6-diiodohexane (PFHxDI) and tridecafluorohexyl iodide (PFHxI), were investigated in the neural differentiation of the mouse embryonic stem cells (mESCs). Without influencing the cytobiological process of the mESCs, PFIs interfered the triploblastic development by increasing ectodermal differentiation, thus promoting subsequent neurogenesis. The temporal regulation of PFIs in Notch-Hes signaling through the targeting of mmu-miRNA-34a-5p provided a substantial explanation for the underlying mechanism of PFI-promoted mESC commitment to the neural lineage. The findings herein provided new knowledge on the potential neurodevelopmental toxicities of PFIs, which would help advance the health risk assessment of these kinds of emerging chemicals.

Constructing an MCF-7 breast cancer cell-based transient transfection assay for screening RARα (Ant)agonistic activities of emerging phenolic compounds.

The screening of compounds with endocrine disrupting effects has been attracting increasing attention due to the continuous release of emerging chemicals into the environment. Testing the (ant)agonistic activities of these chemicals on the retinoic acid receptor α (RARα), a vital nuclear receptor, is necessary to explain their perturbation in the endocrine system in vivo. In the present study, MCF-7 breast carcinoma cells were transiently transfected with a RARα expression vector (pEF1α-RARα-RFP) and a reporter vector containing a retinoic acid reaction element (pRARE-TA-Luc). Under optimized conditions, the performance of the newly constructed system was evaluated for its feasibility in screening the (ant)agonistic effects of emerging phenolic compounds on RARα. The results showed that this transient transfection cell model responded well to stimulation with (ant)agonists of RARα, and the EC50 and IC50 values were 0.87 nM and 2.67 µM for AM580 and Ro41-5253, respectively. Its application in testing several emerging phenolic compounds revealed that triclosan (TCS) and tetrabromobisphenol A (TBBPA) exerted notable RARα antagonistic activities. This newly developed bioassay based on MCF-7 is promising in identifying the agonistic or antagonistic activities of xenobiotics on RARα and has good potential for studying RARα signaling-involved toxicological effects of emerging chemicals of concern.

Assessment of Thyroid Endocrine Disruption Effects of Parabens Using In Vivo, In Vitro, and In Silico Approaches.

The extensive applications of parabens in foods, drugs, and cosmetics cause inevitable exposure to humans. Revealing the developmental toxicity of parabens is of utmost importance regarding their safety evaluation. In this study, the effects of four commonly used parabens, including methyl paraben (20 ∼ 200 µM), ethyl paraben (20 ∼ 100 µM), propyl paraben (5 ∼ 20 µM), and butyl paraben (BuP, 2 ∼ 10 µM), were investigated on the early development of zebrafish embryos and larvae. The underlying mechanisms were explored from the aspect of their disturbance in the thyroid endocrine system using in vivo, in vitro, and in silico assays. Paraben exposure caused deleterious effects on the early development of zebrafish, with BuP displaying the highest toxicity among all, resulting in the exposure concentration-related mortality, decreased hatching rate, reduced body length, lowered heart rate, and the incidence of malformation. Further investigation showed that paraben exposure reduced thyroid hormone levels and disturbed the transcriptional expressions of the target genes in the hypothalamic-pituitary-thyroid axis. Molecular docking analysis combined with in vitro GH3 cell proliferation assay testified that all test parabens exhibited thyroid receptor agonistic activities. The findings confirmed the developmental toxicity of the test parabens and their thyroid endocrine disruption effects, providing substantial evidence on the safety control of paraben-based preservatives.

Diagnostic value of MRI-DWI signal intensity value combined with serum PGI, PGII and CA199 in early gastric cancer.

To explore the diagnostic value of MRI-DWI signal intensity value combined with serum PGI. PGII and CA199 in early gastric cancer. Sixty cases of gastric cancer patients admitted to our hospital from December 2019 to December 2020 were selected as the gastric cancer group and 80 cases of healthy volunteers who underwent physical examination in our hospital during the same period were selected as the healthy group. All the 60 patients underwent MRI-DWI examination, and the pathological diagnosis results were regarded as the gold standard. MRI-DWI images, MRI-DWI signal intensity values of patients with different degrees of gastric cancer differentiation. Serum PGI, PGII and CA199 levels of subjects in the two groups were compared. AUC was used to evaluate the diagnostic value of MRI-DWI signal intensity value combined with serum PGI, PG II and CA199 for early gastric cancer. In the healthy group, T1W1 showed relatively uniform low signal intensity. While T2WI showed no significant increase in signal intensity. In the gastric cancer group. There was diffuse gastric wall thickening, local thickening or mass formation; T1WI and WATS showed slightly lower signal intensity in the lesion area. T2WI, FLAIR and B-TFE showed slightly uneven or moderately increased signal intensity. DWI showed limited diffusion, and the signal intensity increased uniformly or more uniformly, and the range of increase was clear. The signal intensity of MRI-DWI was 89.12 ± 8.14 in patients with low differentiation, 82.17 ± 6.35 in patients with moderate differentiation, and 74.52 ± 4.53 in patients with high differentiation. There were significant differences in the signal intensity of MRI-DWI among the three groups, and the difference was statistically significant (F=12.214, P <0.05). Serum PGI levels of subjects in the gastric cancer group were significantly lower than those in the healthy group, and the levels of PGII and CA199 were significantly higher than that in the healthy group, with statistical significance (P <0.05). The AUC, sensitivity and specificity of MRI-DWI signal intensity value and serum PGI, PGII and CA199 combined indexes in the diagnosis of gastric cancer were significantly higher than those of the independent indexes, with statistical significance (P <0.05). Conclusion: MRI-DWI signal strength value, serum PGI, PGII and CA199 levels are closely related to the occurrence and development of early gastric cancer. The combined detection and diagnosis efficiency is higher, which is helpful to improve the detection rate of early gastric cancer and is worthy of extensive clinical application.

Rare Earth Metal Complexes Supported by a Tripodal Tris(amido) Ligand System Featuring an Arene Anchor.

A new tripodal tris(amido) ligand system featuring an arene anchor was developed and applied to the coordination chemistry of rare earth metals. Two tris(amido) ligands with a 1,3,5-triphenylbenzene backbone were prepared in two steps from commercially available reagents on a gram scale. Salt metathesis and alkane elimination reactions were exploited to prepare mononuclear rare earth metal complexes in moderate to good yields. For salt metathesis reactions, while metal tribromides yielded neutral metal tris(amido) complexes, metal trichlorides led to the formation of ate complexes with an additional chloride bound to the metal center. The new compounds were characterized by X-ray crystallography, elemental analysis, and 1H and 13C nuclear magnetic resonance spectroscopy. The rare earth metal complexes exhibit a trigonal planar coordination geometry for the [MN3] fragment in the solid state rather than a trigonal pyramidal geometry, commonly observed for rare earth metal tris(amido) complexes such as M[N(SiMe3)2]3. Moreover, the arene anchor of the tripodal ligands is engaged in a nonnegligible interaction with the rare earth metal ions. Density functional theory calculations were performed to gain insight into the bonding interactions between the tripodal ligands and the rare earth metal ions. While LUMOs of these rare earth metal complexes are mainly π* orbitals of the arene with a minor component of metal-based orbitals, HOMO-15 and HOMO-16 of a lanthanum complex show that the arene anchor serves as a π donor to the trivalent lanthanum ion.

Developmental Toxicity of Few-Layered Black Phosphorus toward Zebrafish.

Black phosphorus (BP) has extensive applications in various fields. The release of BP into aquatic ecosystems and the potential toxic effects on aquatic organisms are becoming major concerns. Here, we investigated the developmental toxicity of few-layered BP toward the zebrafish. We found that BP could adsorb on the surface of the chorion and could subsequently penetrate within the embryo. After exposure of embryos to 10 mg/L BP, developmental malformations appeared at 96 hpf, especially heart deformities such as pericardial edema and bradycardia, accompanied by severe circulatory system failure. Using transgenic zebrafish larvae, we further characterized cardiovascular defects with cardiac enlargement and impaired cardiac vessels as indicators of damage to the cardiovascular system upon BP exposure. We performed transcriptomic analysis on zebrafish embryos treated with a lower concentration of 2 mg/L. The results showed disruption in genes associated with muscle development, oxygen involved processes, focal adhesion, and VEGF and MAPK signaling pathways. These alterations also indicated that BP carries a risk of developmental perturbation at lower concentrations. This study provides new insights into the effects of BP on aquatic organisms.

Arene-Bridged Dithorium Complexes: Inverse Sandwiches Supported by a δ Bonding Interaction.

A series of arene-bridged dithorium complexes was synthesized via the reduction by potassium graphite of a Th(IV) precursor in the presence of arenes. All these compounds adopt an inverse-sandwich structure, with the arene bridging two thorium centers in a µ-η6,η6-mode. Structural and spectroscopic data support the assignment of two Th(IV) ions and an arene tetraanion, which is an aromatic structure according to Hückel's rule. Arene exchange reactions revealed that the stability of the corresponding compounds follows the series naphthalene ≪ toluene < benzene ≈ biphenyl. Reactivity studies showed that they function as four-electron reductants capable to reduce anthracene, cyclooctatetraene, alkynes, and azobenzene, while a mononuclear thorium anthracene complex could reduce benzene. Density functional theory calculations unveiled that the bonding interactions consist of δ bonds between thorium 6d and 5f orbitals and arene π* orbitals, showing a significant covalent character, able to stabilize highly reduced arene ligands.