Cationic Tropidinyl Scandium Catalyst: A Perfectly Acceptable Substitute for Cationic Half-Sandwich Scandium Catalysts in <i>cis</i>-1,4-Polymerization of Isoprene and Copolymerization with Norbornene

Different nonmetallocene rare earth metal alkyl complexes such as monotropidinyl (Trop) scandium dialkyl complex (Trop)­Sc­(CH₂SiMe₃)₂(THF) (<b>1</b>), ditropidinyl yttrium alkyl complex (Trop)₂Y­(CH₂SiMe₃)­(THF) (<b>3</b>) as well as binuclear lutetium alkyl complex bearing one tetradentate dianionic 6-<i>N</i>-methyl-1,4-cycloheptadienyl (NMCH) ligand [(NMCH)­Lu­(CH₂SiMe₃)­(THF)]₂ (<b>2</b>) have been synthesized in high yields via one-pot acid–base reaction by using of the tris­(trimethylsilylmethyl) rare earth metal complexes with the readily available natural product tropidine. The polymerization experiments indicate that the monotropidinyl scandium dialkyl complex <b>1</b> displays reactivity akin to that of the analogous monocyclopentadienyl scandium dialkyl complexes. In the presence of activator and a small amount of AlMe₃, complex <b>1</b> exhibits similar activities (up to 1.6 × 10⁶ g mol_Sc^–1 h^–1) but higher <i>cis</i>-1,4-selectivities (up to 100%) than (C₅H₅)­Sc­(CH₂SiMe₃)₂(THF) (<i>cis</i>-1,4-selectivity as 95%) in the isoprene polymerization, yielding the pure <i>cis</i>-1,4-PIPs with moderate molecular weights (<i>M</i>_n = 0.5–11.2 × 10⁴ g/mol) and bimodal molecular weight distributions (<i>M</i>_w/<i>M</i>_n = 1.48–6.07). Moreover, the complex <b>1</b>/[Ph₃C]­[B­(C₆F₅)₄/Al^<i>i</i>Bu₃ ternary system also shows good comonomer incorporation ability in the copolymerization of isoprene and norbornene similar to the [C₅Me₄(SiMe₃)]­Sc­(η³-CH₂CHCH₂)₂/activator binary system, affording the random isoprene/norbornene copolymers with a wide range of isoprene contents around 57–91 mol % containing <i>cis</i>-1,4 configuration up to 88%

Underlying Mechanisms for Low-Molecular-Weight Dissolved Organic Matter to Promote Translocation and Transformation of Chlorinated Polyfluoroalkyl Ether Sulfonate in Wheat

Dissolved organic matter (DOM) such as fulvic acid (FA) and humic acid (HA) in soil considerably affects the fate of per- and polyfluoroalkyl substances (PFASs). However, the effect of DOM on their behavior in plants remains unclear. Herein, hydroponic experiments indicate that FA and HA reduce the accumulation of an emerging PFAS of high concern, 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA), in wheat roots by reducing its bioavailability in the solution. Nevertheless, FA with low molecular weight (MW) promotes its absorption and translocation from the roots to the shoots by stimulating the activity and the related genes of the plasma membrane H+-ATPase, whereas high-MW HA shows the opposite effect. Moreover, in vivo and in vitro experiments indicate that 6:2 Cl-PFESA undergoes reductive dechlorination, which is regulated mainly using nitrate reductase and glutathione transferase. HA and FA, particularly the latter, promote the dechlorination of 6:2 Cl-PFESA in wheat by enhancing electron transfer efficiency and superoxide production. Transcriptomic analysis indicates that FA also stimulates catalytic activity, cation binding, and oxidoreductase activity, facilitating 6:2 Cl-PFESA transformation in wheat

Novel Insights into the Promoted Accumulation of Nitro-Polycyclic Aromatic Hydrocarbons in the Roots of Legume Plants

Substituted polycyclic aromatic hydrocarbons (sub-PAHs) are receiving increased attention due to their high toxicity and ubiquitous presence. However, the accumulation behaviors of sub-PAHs in crop roots remain unclear. In this study, the accumulation mechanism of sub-PAHs in crop roots was systematically disclosed by hydroponic experiments from the perspectives of utilization, uptake, and elimination. The obtained results showed an interesting phenomenon that despite not having the strongest hydrophobicity among the five sub-PAHs, nitro-PAHs (including 9-nitroanthracene and 1-nitropyrene) displayed the strongest accumulation potential in the roots of legume plants, including mung bean and soybean. The nitrogen-deficient experiments, inhibitor experiments, and transcriptomics analysis reveal that nitro-PAHs could be utilized by legumes as a nitrogen source, thus being significantly absorbed by active transport, which relies on amino acid transporters driven by H+-ATPase. Molecular docking simulation further demonstrates that the nitro group is a significant determinant of interaction with an amino acid transporter. Moreover, the depuration experiments indicate that the nitro-PAHs may enter the root cells, further slowing their elimination rates and enhancing the accumulation potential in legume roots. Our results shed light on a previously unappreciated mechanism for root accumulation of sub-PAHs, which may affect their biogeochemical processes in soils