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Trapping Highly Reactive Photo-Induced Charge-Transfer Complex Between Amine and Imide by Light
No full textComplexation between two organic molecules can occur either for strong electron donor-acceptor pairs in the ground state known as charge-transfer complexes (CTCs), or for pairs of lesser strength in the excited state such as excimers and exciplexes. However, the characterization of chemically distinct CTCs in solution remains elusive. Here, we report a light-induced, solution-persistent 1:1 CTC between an amine and an imide. The pair is not associated in the ground state at room temperature prior to light exposure. The presence and exact molecular compositions of the CTCs could be directly obtained from high-resolution mass spectrometry. Additional spectroscopic and computational evidence reveals that a kinetically trapped ground-state pair is formed following an exciplex-like process between the amine and the imide after photo-excitation. We show that such a photo-induced complex can be used to conduct photochemistry and store photon energy for producing otherwise photochromic products in the dark
Liquid-Liquid Transition and Ice Crystallization in a Machine-Learned Coarse grained Water Model
No full textMounting experimental evidence supports the existence of a liquid-liquid transition (LLT) in high-pressure supercooled water. However, fast crystallization of supercooled water has impeded identification of the LLT line TLL(p) in experiments. While the most accurate all-atom (AA) water models display a LLT, their computational cost limits investigations of its interplay with ice formation. Coarse-grained (CG) models provide over 100-fold computational efficiency gain over AA models, enabling the study of water crystallization, but have not yet shown to have a LLT. Here we demonstrate that the CG machine-learned water model ML-BOP has a LLT that ends in a critical point at pc = 170±10 MPa and Tc = 181±3 K. The TLL(p) of ML-BOP is almost identical to the one of TIP4P/2005, adding to the similarity in the equation of state of liquid water in both models. Cooling simulations reveal that ice crystallization is fastest at the liquid-liquid transition and its supercritical continuation of maximum heat capacity, supporting a mechanistic relationship between the structural transformation of water to a low-density liquid and ice formation. We find no signature of liquid-liquid criticality in the ice crystallization temperatures. ML-BOP repli-cates the competition between formation of low-density liquid (LDL) and ice observed in ultrafast experiments of decompres-sion of the high-density liquid (HDL) into the region of stability of LDL. The simulations reveal that crystallization occurs prior to the coarsening of the HDL and LDL domains, obscuring the distinction between the highly metastable first order LLT and pronounced structural fluctuations along its supercritical continuation
Photochemical PFAS Degradation in Ion Exchange Resin Regeneration Brine: Effects of Water Matrix Components and Technical Solutions
No full textIon-exchange (IX) is an effective method for PFAS removal from water and wastewater, but the treatment of concentrated PFAS from IX resin regeneration remains a major technical barrier. This study investigates the challenges and solutions associated with photochemical treatment of waste brines from resin regeneration. We first tested the defluorination of perfluorooctanoic acid (PFOA) by UV/sulfite/iodide in synthetic solutions containing individual inorganic and organic species. We identified NO3−, NO2−, and natural organic matter (NOM) as the major inhibitors. NO3− and NO2− quenched hydrated electron (eaq−), but they could be readily removed by increasing the sulfite dose. We used humic acid as a representative NOM. It significantly slowed down defluorination but can be readily removed by ferric flocculation without removing PFOA. The integration of flocculation and UV/S/I treatment successfully treated two waste brines, which primarily contained short-chain PFAS. PFAS removal achieved >99% within 20 hours. The maximum defluorination reached 85% and 70% for the two waste brines, respectively. This study advances UV technologies for PFAS destruction and enhances the sustainability of ion-exchange resin for PFAS removal
Efficient Generation of Torsional Energy Profiles by Multifidelity Gaussian Processes for Hindered-Rotor Corrections
No full textAccurate thermochemistry computations often require a proper treatment of torsional modes. The one-dimensional hindered rotor model has proven to be a computationally efficient solution, given a sufficiently accurate potential energy surface. Methods that provide potential energies at various compromises of uncertainty and computational time demand can be optimally combined within a multifidelity treatment. In this study, we demonstrate how multifidelity modeling leads to: 1. smooth interpolation along low-fidelity scan points with uncertainty estimates, 2. inclusion of high-fidelity data that change the energetic order of conformations, and 3. predict best next-point calculations to extend an initial coarse grid. Our diverse application set comprises molecules, clusters, and transition states of alcohols, ethers, and rings. We discuss limitations for cases where the low-fidelity computation is highly unreliable. Different features of the potential energy curve affect different quantities. To obtain “optimal” fits, we therefore apply strategies ranging from simple minimization of deviations to developing an acquisition function tailored for statistical thermodynamics. Bayesian prediction of best next calculations can save a substantial amount of computation time for one- and multi-dimensional hindered rotors
Directional Bias in Molecular Photogearing Evidenced by LED-coupled Chiral Cryo-HPLC
No full textMolecular gearing systems are technomimetic nanoscale analogues to complex geared machinery in the macroscopic world and are likewise defined as systems incorporating intermeshed elements which perform correlated rotational motions by mechanical engagement. Only recently, new methods to actively drive molecular gearing motions instead of relying on passive thermal activation have been developed. Further progress in this endeavor will pave the way for unidirectional molecular gearing devices with a distinct type of molecular machine awaiting its realization. Within this work an essential step towards this goal is achieved by evidencing directional biases for the light-induced rotations in molecular photogear system 1. Using a custom-designed LED-coupled chiral cryo-HPLC setup for the in-situ irradiation of enantiomeric analytes, an intrinsic selectivity for clockwise or counterclockwise rotations was elucidated experimentally. Significant directional biases in the photogearing (PG) processes and light-induced single bond rotations (SBRs) are observed for photogear 1 with directional preferences of up to 4.8:1. Harnessing these effects will allow to rationally design and construct a fully directional molecular gearing motor in the future
Silylium Ion-Catalyzed α-Arylation of Carboxylic Acids, Amides, and Esters: Efficient Synthesis of Anesthetic and Anti-inflammatory Drugs
No full textA metal-free strategy has been developed for the α-arylation of carboxylic acids, secondary amides, and esters employing arenes as key reagents. This process entails the Lewis-acid catalyzed reductive Friedel–Crafts alkylation of aromatic and heterocyclic arenes with α-ketoacids, facilitated by silane as a reductant in HFIP solvent. The transformation is highly efficient and mild, providing significant advantages over existing protocols. Notably, the method exhibits exceptional tolerance towards various functional groups, enabling late-stage functionalization of pharmaceutical compounds and natural products such as Thymol, and Sesamol. The reaction mechanism has been studied through control experiments, providing valuable insight. This one-step reductive Friedel–Crafts type protocol has been successfully used in the synthesis of various commercially available drugs, such as Adiphenine, Piperidolate, derivatives of Ketoprofen, Ibuprofen, and Flurbiprofen, and Bromopropylate pesticide. Furthermore, after the gram-scale synthesis, the solvent (HFIP) was recovered, demonstrating the method\u27s suitability for industrial applications
Synthesis of Polyurethanes Through the Oxidative Decarboxylation of Oxamic Acids: a New Gateway Toward Self-blown Foams
No full textPolyurethane (PU) thermoplastics and thermosets were prepared through the step-growth polymerization of in situ generated polyisocyanates through the decarboxylation of polyoxamic acids, in the presence of phenyliodine diacetate (PIDA), and polyols. The CO2 produced during the reaction allowed the access to self-blown polyurethane foams through an endogenous chemical blowing. The acetic acid released from ligand exchange at the iodine center was also shown to accelerate the polymerization reaction, avoiding the recourse to an additional catalyst. Changing simple parameters during the production process allowed us to access flexible PU foams with a wide range of properties
“Nano-Skeleton” Si-SiOx@C Anodes towards Highly Stable Lithium-ion Batteries
No full textA fragile solid-electrolyte interphase (SEI) layer due to the volume expansion of silicon cannot sufficiently prevent side reactions and electrolyte consumption and restricts the application of silicon anodes in lithium-ion batteries with high cycling stability. Herein, a carbon nanotube (CNT) supported “nano-skeleton” structure with high mechanical property and improved conductive pathways is designed by twining CNTs with in-situ grown SiOx@C and carbon-wrapped Si nanoparticles. The CNT “nano-skeleton” can improve electrical contact between particles, promoting the formation of a denser and more homogenous SEI layer. Moreover, the buffer region granted by the CNTs can tolerate the volume expansions of Si avoiding the repeated destruction of the SEI layer during continuous lithiation and delithiation processes. Combined with these advantages, the anode with optimal CNT content can deliver a high capacity (918 mAh·g-1 at 200 mA·g-1) and high capacity retention (74% after 300 cycles) with relieved volume expansion (71.4%). The capacity of the NMC111 full cell retains about 70 mAh·g-1 after 500 cycles at 100 mAh·g-1 with capacity retention of 72%
Lignin-based Mucin-mimicking Antiviral Hydrogels with Enzyme Stability and Tunable Porosity
No full textMucus is a complex hydrogel acting as a defensive and protective barrier in various parts of the human body. The structure and composition of mucus play an important role in maintaining barrier properties by acting as a filter for the diffusion of biomolecules and pathogens. The rise in viral infections has underscored the importance of advancing research into mucus-mimicking hydrogels for the efficient design of antiviral agents. However, the performance of an antiviral strategy should not only be assessed based on its efficacy in inhibiting infections but also based on its sustainability. Herein, we demonstrate the gram-scale synthesis of biocompatible, lignin-based virus-binding inhibitors that reduce waste and ensure long-term availability. The lignin-based inhibitors were equipped with sulfate moieties, which are known binding partners for many viruses including SARS-CoV-2 and herpes viruses. In addition, crosslinking the synthesized inhibitors yielded hydrogels that mimicked native mucus with respect to surface functionality and rheology. It is found that the degree of sulfation has a very strong impact on the mesh size distribution of the hydrogels, which provides a new means to fine-tune steric and electrostatic contributions of the virus-hydrogel interaction. This feature strongly impacts the sequestration capability of the lignin-based hydrogels, which is demonstrated by infection inhibition assays involving human herpes simplex virus-1, influenza A viruses, and the bacterium Escherichia coli (E. coli). For HSV-1 and E. coli, these measurements showed a reduction in plaque (HSV-1) and colony-forming units (E. coli) by more than 4 orders of magnitude, indicating potent inhibition by the lignin-based hydrogels. Taken together, the sulfated lignin hydrogel is an excellent scaffold for large-scale synthesis of sustainable, biocompatible, and highly efficient pathogen-binding inhibitors
Environmental Sustainability Perception in Industry: A Prospective Eco-Innovation Strategy Implementation in an Electrical Motor Manufacturing Plant
No full textThis study focuses on the implementation of eco-innovation strategies in an electrical motor manufacturing plant to promote environmental sustainability. The evaluation process for cleaner product implementation in the plant involves gathering technical and environmental data, identifying pollution sources, and implementing cleaner production tactics. Electrical motor manufacturers can reduce their environmental impact, enhance operational efficiency, and increase cost-effectiveness by adopting cleaner production techniques. The study examines the planning phase of ISO 14001 implementation processes and its integration with environmental requirements in the electrical motor manufacturing industry. The findings highlight the importance of environmental consequences and regulatory requirements in the design phase and overall organization of environmental management systems