Faraday Discussions最新文献

{"title":"Reaction interferometry with ultracold molecules","authors":"Jeshurun Luke, Lingbang Zhu, Yi-Xiang Liu and Kang-Kuen Ni","doi":"10.1039/D3FD00175J","DOIUrl":"10.1039/D3FD00175J","url":null,"abstract":"<p >We propose to coherently control the ultracold 2KRb → K<small>₂</small> + Rb<small>₂</small> reaction product state distribution <em>via</em> quantum interference. By leveraging that the nuclear spin degrees of freedom in the reaction maintain coherence, which was demonstrated in Liu, Zhu <em>et al.</em>, <em>arXiv</em>, 2023, arXiv:2310.07620, https://doi.org/10.48550/arXiv.2310.07620, we explore the concept of a “reaction interferometer”. Such an interferometer involves splitting one KRb molecular cloud into two, imprinting a well-defined relative phase between them, recombining the clouds for reactions, and measuring the product state distribution. We show that the interference patterns provide a mechanism to coherently control the product states, and specific product channels also serve as an entanglement witness of the atoms in the reactant KRb molecule.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reaction dynamics of the methoxy anion CH3O− with methyl iodide CH3I","authors":"Thomas Gstir, David Sundelin, Tim Michaelsen, Atilay Ayasli, Dasarath Swaraj, Jerin Judy, Fabio Zappa, Wolf Geppert and Roland Wester","doi":"10.1039/D3FD00164D","DOIUrl":"10.1039/D3FD00164D","url":null,"abstract":"<p >Studying larger nucleophiles in bimolecular nucleophilic substitution (S<small>_N</small>2) reactions bridges the gap from simple model systems to those relevant to organic chemistry. Therefore, we investigated the reaction dynamics between the methoxy anion (CH<small>₃</small>O<small>⁻</small>) and iodomethane (CH<small>₃</small>I) in our crossed-beam setup combined with velocity map imaging at the four collision energies 0.4, 0.7, 1.2, and 1.6 eV. We find the two ionic products I<small>⁻</small> and CH<small>₂</small>I<small>⁻</small>, which can be attributed to the S<small>_N</small>2 and proton transfer channels, respectively. The proton transfer channel progresses in a previously observed fashion from indirect to direct scattering with increasing collision energy. Interestingly, the S<small>_N</small>2 channel exhibits direct dynamics already at low collision energies. Both the direct stripping, leading to forward scattering, and the direct rebound mechanism, leading to backward scattering into high angles, are observed.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d3fd00164d?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature dependent stereodynamics in surface scattering measured through subtle changes in the molecular wave function†","authors":"Helen Chadwick and Gil Alexandrowicz","doi":"10.1039/D4FD00007B","DOIUrl":"10.1039/D4FD00007B","url":null,"abstract":"<p >A magnetically manipulated molecular beam technique is used to change the rotational orientation of H<small>₂</small> molecules which collide with a stepped Cu(511) surface and explore how the polarisation dependence of molecules scattering into the specular channel changes as a function of surface temperature. At all temperatures, H<small>₂</small> molecules that are rotating like cartwheels are more likely to be scattered into the specular channel than those that are rotating like helicopters. Furthermore, the scattered molecules are more likely to be rotating like cartwheels, regardless of their state before the collision. Increasing the temperature of the Cu(511) surface causes the polarisation effects to become stronger, with the scattering becoming more selective for H<small>₂</small> with cartwheel like rotation. Therefore, scattering a molecular beam of H<small>₂</small> from a Cu(511) surface and taking the molecules scattered into the specular channel provides a method to create a rotationally polarised beam of H<small>₂</small>, where the polarisation can be tuned by changing the surface temperature. In contrast, the rotational orientation dependence observed for specular scattering from a flat Cu(111) surface is independent of surface temperature within the same temperature range.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d4fd00007b?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the biocatalytic synthesis of silicone polymers","authors":"Yuqing Lu and Lu Shin Wong","doi":"10.1039/D4FD00003J","DOIUrl":"10.1039/D4FD00003J","url":null,"abstract":"<p >Polysiloxanes, with poly(dimethyl)siloxane (PDMS) being the most common example, are widely used in various industrial and consumer applications due to the physicochemical properties imparted by their Si–O–Si backbone structure. The conventional synthesis of PDMS involves the hydrolysis of dichlorodimethylsilane, which raises environmental concerns due to the usage of chlorinated compounds. Herein, a biocatalytic approach for PDMS synthesis is demonstrated using silicatein-α (Silα), an enzyme from marine sponges that is known to catalyse the hydrolysis and condensation of Si–O bonds. Using dialkoxysilane precursors, it was found that Silα catalyses the formation of PDMS in non-aqueous media, yielding polymers with higher molecular weights (approximately 1000–2000 Da). However, on prolonged exposure, the gradual degradation of the polymers was also observed. Overall these observations indicate that Silα catalyses the formation polysiloxanes, demonstrating the potential of biocatalysis for more sustainable polysiloxane production.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d4fd00003j?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reaction dynamics of S(3P) with 1,3-butadiene and isoprene: crossed-beam scattering, low-temperature flow experiments, and high-level electronic structure calculations†","authors":"Jinxin Lang, Casey D. Foley, Shameemah Thawoos, Abbas Behzadfar, Yanan Liu, Judit Zádor and Arthur G. Suits","doi":"10.1039/D4FD00009A","DOIUrl":"10.1039/D4FD00009A","url":null,"abstract":"<p >Sulfur atoms serve as key players in diverse chemical processes, from astrochemistry at very low temperature to combustion at high temperature. Building upon our prior findings, showing cyclization to thiophenes following the reaction of ground-state sulfur atoms with dienes, we here extend this investigation to include many additional reaction products, guided by detailed theoretical predictions. The outcomes highlight the complex formation of products during intersystem crossing (ISC) to the singlet surfaces. Here, we employed crossed-beam velocity map imaging and high-level <em>ab initio</em> methods to explore the reaction of S(<small>³</small>P) with 1,3-butadiene and isoprene under single-collision conditions and in low-temperature flows. For the butadiene reaction, our experimental results show the formation of thiophene <em>via</em> H<small>₂</small> loss, a 2<em>H</em>-thiophenyl radical through H loss, and thioketene through ethene loss at a slightly higher collision energy compared to previous observations. Complementary Chirped-Pulse Fourier-Transform mmWave spectroscopy (CP-FTmmW) measurements in a uniform flow confirmed the formation of thioketene in the reaction at 20 K. For the isoprene reaction, we observed analogous products along with the 2<em>H</em>-thiophenyl radical arising from methyl loss and C<small>₃</small>H<small>₄</small>S (loss of ethene or H<small>₂</small> + acetylene). CP-FTmmW detected the formation of thioformaldehyde <em>via</em> loss of 1,3-butadiene, again in the 20 K flow. Coupled-cluster calculations on the pathways found by the automated kinetic workflow code KinBot support these findings and indicate ISC to the singlet surface, leading to the generation of various long-lived intermediates, including 5-membered heterocycles.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inelastic scattering of NO(A2Σ+) + CO2: rotation–rotation pair-correlated differential cross sections","authors":"Joseph G. Leng, Thomas R. Sharples, Martin Fournier, Kenneth G. McKendrick, Luca Craciunescu, Martin J. Paterson and Matthew L. Costen","doi":"10.1039/D3FD00162H","DOIUrl":"10.1039/D3FD00162H","url":null,"abstract":"<p >A crossed beam velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs) for the rotationally inelastic scattering of NO(A<small>²</small>Σ<small>⁺</small>, <em>v</em> = 0, <em>j</em> = 0.5) with CO<small>₂</small>, as a function of both NO(A, <em>v</em> = 0, <em>N</em>′) final state and the coincident final rotational energy of the CO<small>₂</small>. The DCSs are dominated by forward-peaked scattering for all <em>N</em>′, with significant rotational excitation of CO<small>₂</small>, and a small backward scattered peak is also observed for all final <em>N</em>′. However, no rotational rainbow scattering is observed and there is no evidence for significant product rotational angular momentum polarization. New <em>ab initio</em> potential energy surface calculations at the PNO-CCSD(T)-F12b level of theory report strong attractive forces at long ranges with significant anisotropy relative to both NO and CO<small>₂</small>. The absence of rotational rainbow scattering is consistent with removal of low-impact-parameter collisions <em>via</em> electronic quenching, in agreement with the literature quenching rates of NO(A) by CO<small>₂</small> and recent electronic structure calculations. We propose that high-impact-parameter collisions, that do not lead to quenching, experience strong anisotropic attractive forces that lead to significant rotational excitation in both NO and CO<small>₂</small>, depolarizing product angular momentum while leading to forward and backward glory scattering.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d3fd00162h?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of rational enzyme engineering in a new route to etonogestrel and levonorgestrel: carbonyl reductase bioreduction of ethyl secodione†","authors":"Daniel F. A. R. Dourado, Andrew S. Rowan, Sergej Maciuk, Gareth Brown, Darren Gray, Jenny Spratt, Alexandra T. P. Carvalho, Dražen Pavlović, Fernando Tur, Jill Caswell, Derek J. Quinn, Thomas S. Moody and Stefan Mix","doi":"10.1039/D4FD00011K","DOIUrl":"10.1039/D4FD00011K","url":null,"abstract":"<p >Women in developing countries still face enormous challenges when accessing reproductive health care. Access to voluntary family planning empowers women allowing them to complete their education and join the paid workforce. This effectively helps to end poverty, hunger and promotes good health for all. According to the United Nations (UN) organization, in 2022, an estimated 257 million women still lacked access to safe and effective family planning methods globally. One of the main barriers is the associated cost of modern contraceptive methods. Funded by the Bill &amp; Melinda Gates Foundation, Almac Group worked on the development of a novel biocatalytic route to etonogestrel and levonorgestrel, two modern contraceptive APIs, with the goal of substantially decreasing the cost of production and so enabling their use in developing nations. This present work combines the selection and engineering of a carbonyl reductase (CRED) enzyme from Almac’s selectAZyme™ panel, with process development, to enable efficient and economically viable bioreduction of ethyl secodione to (13<em>R</em>,17<em>S</em>)-secol, the key chirality introducing intermediate en route to etonogestrel and levonorgestrel API. CRED library screening returned a good hit with an Almac CRED from <em>Bacillus weidmannii</em>, which allowed for highly stereoselective bioreduction at low enzyme loading of less than 1% w/w under screening assay conditions. However, the only co-solvent tolerated was DMSO up to ∼30% v/v, and it was impossible to achieve reaction completion with any enzyme loading at substrate titres of 20 g L<small>⁻¹</small> and above, due to the insolubility of the secodione. This triggered a rapid enzyme engineering program fully based on computational mutant selection. A small panel of 93 CRED mutants was rationally designed to increase the catalytic activity as well as thermal and solvent stability. The best mutant, Mutant-75, enabled a reaction at 45 °C to go to completion at 90 g L<small>⁻¹</small> substrate titre in a buffer/DMSO/heptane reaction medium fed over 6 h with substrate DMSO stock solution, with a low enzyme loading of 3.5% w/w wrt substrate. In screening assay conditions, Mutant-75 also showed a 2.2-fold activity increase. Our paper shows which computations and rational decisions enabled this outcome.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probing the interfacial structure of aqueous surfactants through helium atom evaporation†","authors":"Xiao-Fei Gao, David J. Hood, Timothy H. Bertram and Gilbert M. Nathanson","doi":"10.1039/D3FD00177F","DOIUrl":"10.1039/D3FD00177F","url":null,"abstract":"<p >Dissolved helium atoms evaporate from liquids in super-Maxwellian speed distributions because their interactions are too weak to enforce full thermal equilibration at the surface as they are “squeezed” out of solution. The excess speeds of these He atoms reflect their final interactions with solvent and solute molecules at the surfaces of water and other liquids. We extend this observation by monitoring He atom evaporation from salty water solutions coated with surfactants. These surface-active molecules span neutral, anionic, and cationic amphiphiles: butanol, 3-methyl-1-butanol, pentanol, pentanoic acid, pentanoate, tetrabutylammonium, benzyltrimethylammonium, hexyltrimethylammonium, and dodecyltrimethylammonium, each characterized by surface tension measurements. The helium energy distributions, recorded in vacuum using a salty water microjet, reveal a sharp distinction between neutral and ionic surfactant films. Helium atoms evaporate through neutral surfactant monolayers in speed distributions that are similar to a pure hydrocarbon, reflecting the common alkyl chains of both. In contrast, He atoms appear to evaporate through ionic surfactant layers in distributions that are closer to pure salty water. We speculate that the ionic surfactants distribute themselves more loosely and deeply through the top layers of the aqueous solution than do neutral surfactants, with gaps between the surfactants that may be filled with salty water. This difference is supported by prior molecular dynamics simulations and ion scattering measurements of surfactant solutions.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139757600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scattering resonances in the rotational excitation of HDO by Ne and normal-H2: theory and experiment†","authors":"Ricardo Manuel García-Vázquez, Astrid Bergeat, Otoniel Denis-Alpizar, Alexandre Faure, Thierry Stoecklin and Sébastien B. Morales","doi":"10.1039/D3FD00168G","DOIUrl":"10.1039/D3FD00168G","url":null,"abstract":"<p >The rotational excitation of a singly deuterated water molecule (HDO) by a heavy atom (Ne) and a light diatomic molecule (H<small>₂</small>) is investigated theoretically and experimentally in the near-threshold regime. Crossed-molecular-beam measurements with a variable crossing angle are compared to close-coupling calculations based on high-accuracy potential energy surfaces. The two lowest rotational transitions, 0<small>₀₀</small> → 1<small>₀₁</small> and 0<small>₀₀</small> → 1<small>₁₁</small>, are probed in detail and a good agreement between theory and experiment is observed for both transitions in the case of HDO + Ne, where scattering resonances are however blurred out experimentally. In the case of HDO + H<small>₂</small>, the predicted theoretical overlapping resonances are faithfully reproduced by experiment for the 0<small>₀₀</small> → 1<small>₁₁</small> transition, while the calculated strong signal for the 0<small>₀₀</small> → 1<small>₀₁</small> transition is not detected. Future work is needed to reconcile this discrepancy.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d3fd00168g?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139657042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isomeric and rotational effects in the chemi-ionisation of 1,2-dibromoethene with metastable neon atoms†","authors":"Amit Mishra, Junggil Kim, Sang Kyu Kim and Stefan Willitsch","doi":"10.1039/D3FD00172E","DOIUrl":"10.1039/D3FD00172E","url":null,"abstract":"<p >The specific geometry of a molecule can have a pronounced influence on its chemical reactivity. However, experimental data on reactions of individual molecular isomers are still sparse because they are often difficult to separate and frequently interconvert into one another under ambient conditions. Here, we employ a novel crossed-beam experiment featuring an electrostatically controlled molecular beam combined with a source for radicals and metastables to spatially separate the <em>cis</em> and <em>trans</em> stereoisomers as well as individual rotational states of 1,2-dibromoethene and study their specific reactivities in the chemi-ionisation reaction with excited neon atoms. The experiments reveal pronounced isomeric and rotational specificities in the rates and product branching ratios of the reaction. The present study underlines the importance and combined role of molecular geometry and of rotational motion in the dynamics of chemi-ionisation reactions.</p>","PeriodicalId":49075,"journal":{"name":"Faraday Discussions","volume":null,"pages":null},"PeriodicalIF":3.4,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/fd/d3fd00172e?page=search","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139657344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}