Today, there is a huge need for highly efficient and sustainable energy resources to tackle environmental degradation and energy crisis. We have analyzed the electronic, mechanical and thermoelectric (TE) characteristics of two-dimensional (2D) BiSbTeX2 (X = S, Se and Te) and Janus BiSbTeXY (X/Y = S, Se and Te) monolayers by implementing first principles simulations. These monolayers' dynamic stability and thermal stability have been demonstrated through phonon dispersion spectra and ab initio molecular dynamics (AIMD) simulations, respectively. The band structure of these monolayers can be tuned by applying uniaxial and biaxial strains. The investigated lattice thermal conductivity (κl) for these monolayers lies between 0.23 and 0.37 W m−1 K−1 at 300 K. For a more precise calculation of the scattering rate, we implemented electron–phonon coupling (EPC) and spin–orbit coupling effects to calculate the transport properties. For p(n)-type carriers, the power factor of these monolayers is predicted to be as high as 2.08 × 10−3 W m−1 K−2 and (0.47 × 10−3 W m−1 K−2) at 300 K. The higher thermoelectric figure of merit (ZT) of p-type carriers at 300 K is obtained because of their very low value of κl and high power factor. Our theoretical investigation predicts that these monolayers can be potential candidates for fabricating highly efficient thermoelectric power generators.
如今，人们亟需高效、可持续的能源资源来应对环境恶化和能源危机。我们通过第一性原理模拟分析了二维（2D）BiSbTeX2（X = S、Se 和 Te）和 Janus BiSbTeXY（X/Y = S、Se 和 Te）单层的电子、机械和热电（TE）特性。这些单层的动态稳定性和热稳定性已分别通过声子频散谱和非初始分子动力学（AIMD）模拟得到证实。通过施加单轴和双轴应变，可以调整这些单层的带状结构。为了更精确地计算散射率，我们采用了电子-声子耦合（EPC）和自旋轨道耦合效应来计算传输特性。对于 p(n) 型载流子，预测这些单层的功率因数高达 2.08 × 10-3 W m-1 K-2，在 300 K 时为 (0.47 × 10-3 W m-1 K-2)。我们的理论研究预测，这些单层材料可能成为制造高效热电发电机的潜在候选材料。
{"title":"Two-dimensional BiSbTeX2 (X = S, Se, Te) and their Janus monolayers as efficient thermoelectric materials","authors":"KM Sujata, Poonam Chauhan, Nidhi Verma, Rekha Garg Solanki, Ashok Kumar","doi":"10.1039/d4cp02750g","DOIUrl":"https://doi.org/10.1039/d4cp02750g","url":null,"abstract":"Today, there is a huge need for highly efficient and sustainable energy resources to tackle environmental degradation and energy crisis. We have analyzed the electronic, mechanical and thermoelectric (TE) characteristics of two-dimensional (2D) BiSbTeX<small><sub>2</sub></small> (X = S, Se and Te) and Janus BiSbTeXY (X/Y = S, Se and Te) monolayers by implementing first principles simulations. These monolayers' dynamic stability and thermal stability have been demonstrated through phonon dispersion spectra and <em>ab initio</em> molecular dynamics (AIMD) simulations, respectively. The band structure of these monolayers can be tuned by applying uniaxial and biaxial strains. The investigated lattice thermal conductivity (<em>κ</em><small><sub>l</sub></small>) for these monolayers lies between 0.23 and 0.37 W m<small><sup>−1</sup></small> K<small><sup>−1</sup></small> at 300 K. For a more precise calculation of the scattering rate, we implemented electron–phonon coupling (EPC) and spin–orbit coupling effects to calculate the transport properties. For p(n)-type carriers, the power factor of these monolayers is predicted to be as high as 2.08 × 10<small><sup>−3</sup></small> W m<small><sup>−1</sup></small> K<small><sup>−2</sup></small> and (0.47 × 10<small><sup>−3</sup></small> W m<small><sup>−1</sup></small> K<small><sup>−2</sup></small>) at 300 K. The higher thermoelectric figure of merit (<em>ZT</em>) of p-type carriers at 300 K is obtained because of their very low value of <em>κ</em><small><sub>l</sub></small> and high power factor. Our theoretical investigation predicts that these monolayers can be potential candidates for fabricating highly efficient thermoelectric power generators.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486288","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}
Javier Luque Di Salvo, Santiago Agustín Maldonado-Ochoa, Guillermina Leticia Luque, Andrea Calderón, Victoria Bracamonte, Fabián Vaca Chavez, Daniel E Barraco, Alen Vizintin, Robert Dominko, Ezequiel Pedro Marcos Leiva, GIORGIO DELUCA
Li-S batteries are promising alternatives due to their proven increased gravimetric capacity compared to Li-ion batteries. However, their development is hindered by many technical issues, one of the most challenging being the dissolution and shuttle of polysulfide species, which causes irreversible loss of cathode material leading to rapid capacity fading. Among the possible strategies to mitigate this effect, the choice of suitable solvents is easy to implement and has large room for improvement. To guide this quest, computationally-aided optimization is a powerful tool, provided that suitable descriptors are used to screen possible solvents. In this work, molecular dynamics simulations were performed for a typical lithium polysulfide 〖Li〗_2 S_6 dissolved in different solvents. Diffusion coefficients and their related activation energies were calculated, and thermodynamic properties like solvation energies and entropies were also evaluated. Additionally, a theoretical framework for computing the relative solubilities of lithium polysulfide is provided. For the set of solvents considered, we found that the system's viscosity appears as an important descriptor to correlate with different system properties. The donor number of the solvent also appears as a valid descriptor, for low-viscosity solvents. In general, it was found that higher viscosity solvents lead to lower diffusion rates and higher polysulfide solubility. These results suggest that the optimal choice to reduce the shuttle is a trade-off between high-viscosity solvents to reduce polysulfide diffusion and low-viscosity solvents to reduce its solubility, which could be further improved by properly tuning the donor number.
{"title":"Diffusion and thermodynamic properties of lithium polysulfides in different solvents: a molecular dynamics approach","authors":"Javier Luque Di Salvo, Santiago Agustín Maldonado-Ochoa, Guillermina Leticia Luque, Andrea Calderón, Victoria Bracamonte, Fabián Vaca Chavez, Daniel E Barraco, Alen Vizintin, Robert Dominko, Ezequiel Pedro Marcos Leiva, GIORGIO DELUCA","doi":"10.1039/d4cp03352c","DOIUrl":"https://doi.org/10.1039/d4cp03352c","url":null,"abstract":"Li-S batteries are promising alternatives due to their proven increased gravimetric capacity compared to Li-ion batteries. However, their development is hindered by many technical issues, one of the most challenging being the dissolution and shuttle of polysulfide species, which causes irreversible loss of cathode material leading to rapid capacity fading. Among the possible strategies to mitigate this effect, the choice of suitable solvents is easy to implement and has large room for improvement. To guide this quest, computationally-aided optimization is a powerful tool, provided that suitable descriptors are used to screen possible solvents. In this work, molecular dynamics simulations were performed for a typical lithium polysulfide 〖Li〗_2 S_6 dissolved in different solvents. Diffusion coefficients and their related activation energies were calculated, and thermodynamic properties like solvation energies and entropies were also evaluated. Additionally, a theoretical framework for computing the relative solubilities of lithium polysulfide is provided. For the set of solvents considered, we found that the system's viscosity appears as an important descriptor to correlate with different system properties. The donor number of the solvent also appears as a valid descriptor, for low-viscosity solvents. In general, it was found that higher viscosity solvents lead to lower diffusion rates and higher polysulfide solubility. These results suggest that the optimal choice to reduce the shuttle is a trade-off between high-viscosity solvents to reduce polysulfide diffusion and low-viscosity solvents to reduce its solubility, which could be further improved by properly tuning the donor number.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486304","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":"Fundamental basis of mechanochemical reactivity.","authors":"Adam A L Michalchuk, Francesco Delogu","doi":"10.1039/d4cp90153c","DOIUrl":"https://doi.org/10.1039/d4cp90153c","url":null,"abstract":"","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":2.9,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142453713","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}
While preferential hydrogen bond network structures of cold protonated alcohol clusters H+(ROH)n are generally switched from a linear type to a cyclic one at n = 4 ~ 5, those of protonated 2,2,2-trifluoroethanol (TFE) clusters maintain linear type structures at least in the size range of n = 3 – 7. To explore the origin of the strong linear type network preference of H+(TFE)n, infrared spectra of protonated mixed clusters H+(TFE)m(ethanol)n (m + n = 5) were measured. An efficient structure sampling technique using parallelized basin-hopping algorithms and deep-learning neural network potentials is developed to search for essential isomers of the mixed clusters. Vibrational simulations based on the harmonic superposition approximation were compared with the observed spectra to identify the major isomer component at each mixing ratio. It was found that the formation of the cyclic structure occurs only in n ≥ 3 of the mixed clusters, in which the proton solvating sites and the double acceptor site are occupied by ethanol. The crucial role of the stability of the double acceptor site in the cyclic structure formation is discussed.
冷质子化醇簇 H+(ROH)n的氢键网络结构一般在 n = 4 ~ 5 时从线型转变为环型，而质子化 2,2,2-三氟乙醇（TFE）簇的氢键网络结构至少在 n = 3 - 7 的尺寸范围内保持线型。为了探索 H+(TFE)n 强烈的线型网络偏好的起源，我们测量了质子化混合簇 H+(TFE)m(乙醇)n（m + n = 5）的红外光谱。利用并行化跳盆算法和深度学习神经网络势能，开发了一种高效的结构采样技术，以寻找混合簇的基本同分异构体。将基于谐波叠加近似的振动模拟与观测光谱进行比较，以确定每个混合比下的主要异构体成分。结果发现，只有在 n ≥ 3 的混合团簇中才会形成环状结构，其中质子溶解位点和双受体位点被乙醇占据。讨论了双受体位点的稳定性在环状结构形成中的关键作用。
{"title":"Hydrogen Bond Network Structures of Protonated 2,2,2-Trifluoroethanol/Ethanol Mixed Clusters Probed by Infrared Spectroscopy Combined with a Deep-learning Structure Sampling Approach: The Origin of the Linear Type Network Preference in Protonated Fluoroalcohol Clusters†","authors":"Po-Jen Hsu, Atsuya Mizuide, Jer-Lai Kuo, Asuka Fujii","doi":"10.1039/d4cp03534h","DOIUrl":"https://doi.org/10.1039/d4cp03534h","url":null,"abstract":"While preferential hydrogen bond network structures of cold protonated alcohol clusters H+(ROH)n are generally switched from a linear type to a cyclic one at n = 4 ~ 5, those of protonated 2,2,2-trifluoroethanol (TFE) clusters maintain linear type structures at least in the size range of n = 3 – 7. To explore the origin of the strong linear type network preference of H+(TFE)n, infrared spectra of protonated mixed clusters H+(TFE)m(ethanol)n (m + n = 5) were measured. An efficient structure sampling technique using parallelized basin-hopping algorithms and deep-learning neural network potentials is developed to search for essential isomers of the mixed clusters. Vibrational simulations based on the harmonic superposition approximation were compared with the observed spectra to identify the major isomer component at each mixing ratio. It was found that the formation of the cyclic structure occurs only in n ≥ 3 of the mixed clusters, in which the proton solvating sites and the double acceptor site are occupied by ethanol. The crucial role of the stability of the double acceptor site in the cyclic structure formation is discussed.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486308","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}
Valeria Stagno, Otto Mankinen, Sarah Mailhiot, Ville-Veikko Telkki, Silvia Capuani
Chemical, physical, and biological decay may partially or totally hide the historical and technological information carried by waterlogged wood. Investigation of the above-mentioned decay processes is essential to assess the wood preservation state, and it is important to find new methods for the consolidation and safeguarding of wooden archaeological heritage. A conventional method for assessing the wood preservation state is light microscopy. However, the method requires sample slicing, which is destructive and challenging when dealing with fragile and spongy submerged remains of heritage wood. To this end, a promising alternative non-destructive technique is proton nuclear magnetic resonance (1H-NMR) which considers wood as a porous system. This work aimed to perform a comprehensive analysis of structures, porosity, water distribution, decay, and possible structural inclusions of three archaeological waterlogged wood fragments of the Roman age using NMR relaxometry, micro-imaging (μ-MRI), NMR diffusometry, and NMR cryoporometry. The results were compared with a similar analysis of the three contemporary wood samples of the same species. The multimodal approach presented in this study allowed us to cover all the dimensional scales of wood, from nanometers to sub-millimeters, and reconstruct the alteration of the entire archaeological wood fragment caused by degradation.
{"title":"Comprehensive characterization of waterlogged archaeological wood by NMR relaxometry, diffusometry, micro-imaging and cryoporometry","authors":"Valeria Stagno, Otto Mankinen, Sarah Mailhiot, Ville-Veikko Telkki, Silvia Capuani","doi":"10.1039/d4cp02697g","DOIUrl":"https://doi.org/10.1039/d4cp02697g","url":null,"abstract":"Chemical, physical, and biological decay may partially or totally hide the historical and technological information carried by waterlogged wood. Investigation of the above-mentioned decay processes is essential to assess the wood preservation state, and it is important to find new methods for the consolidation and safeguarding of wooden archaeological heritage. A conventional method for assessing the wood preservation state is light microscopy. However, the method requires sample slicing, which is destructive and challenging when dealing with fragile and spongy submerged remains of heritage wood. To this end, a promising alternative non-destructive technique is proton nuclear magnetic resonance (<small><sup>1</sup></small>H-NMR) which considers wood as a porous system. This work aimed to perform a comprehensive analysis of structures, porosity, water distribution, decay, and possible structural inclusions of three archaeological waterlogged wood fragments of the Roman age using NMR relaxometry, micro-imaging (μ-MRI), NMR diffusometry, and NMR cryoporometry. The results were compared with a similar analysis of the three contemporary wood samples of the same species. The multimodal approach presented in this study allowed us to cover all the dimensional scales of wood, from nanometers to sub-millimeters, and reconstruct the alteration of the entire archaeological wood fragment caused by degradation.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486286","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}
A graphical abstract is available for this content
本内容有图解摘要
{"title":"Fundamental basis of mechanochemical reactivity","authors":"Adam A. L. Michalchuk, Francesco Delogu","doi":"10.1039/d4cp90153c","DOIUrl":"https://doi.org/10.1039/d4cp90153c","url":null,"abstract":"A graphical abstract is available for this content","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486287","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}
Li Deng, Xiang Yin, Yanzhao Wu, Junwei Tong, Gaowu W. Qin, Xianmin Zhang
Quantum anomalous Hall (QAH) insulators with dissipation-less chiral edge channels provide the ideal platforms for the exploration of topological materials and low-power spintronic devices. However, the ultralow operation temperature and small nontrivial gap are the bottlenecks for QAH insulators towards future applications. Here, a new family of QAH insulators, that is, the Janus M2XS2Se2 (M = V, Ti; X = W, Mo) monolayers are proposed, which are ferromagnets with large perpendicular magnetic anisotropy (PMA) and high Curie temperature above room-temperature. Moreover, the present M2XS2Se2 monolayers hold sizable nontrivial topological gaps, resulting in the 1st chiral edge state with Chern number C=-1. Unexpectedly, there also exists an occupied 2nd chiral edge state below the Fermi level. Although all M2XS2Se2 monolayers remain the characteristic of PMA by applying the biaxial strain, various topological phase transitions are present. V2WS2Se2 monolayer preserves the QAH state regardless of strain, while the V2MoS2Se2 and Ti2WS2Se2 monolayers transform from QAH states to metallic states under the tensile strains. The present M2XS2Se2 monolayers show the competitive advantages among the reported materials for the development of topological electronic devices.
{"title":"Multi-level chiral edge states in Janus M2XS2Se2 (M = V, Ti; X = W, Mo) monolayers with high Curie temperature and sizable nontrivial topological gaps","authors":"Li Deng, Xiang Yin, Yanzhao Wu, Junwei Tong, Gaowu W. Qin, Xianmin Zhang","doi":"10.1039/d4cp03325f","DOIUrl":"https://doi.org/10.1039/d4cp03325f","url":null,"abstract":"Quantum anomalous Hall (QAH) insulators with dissipation-less chiral edge channels provide the ideal platforms for the exploration of topological materials and low-power spintronic devices. However, the ultralow operation temperature and small nontrivial gap are the bottlenecks for QAH insulators towards future applications. Here, a new family of QAH insulators, that is, the Janus M2XS2Se2 (M = V, Ti; X = W, Mo) monolayers are proposed, which are ferromagnets with large perpendicular magnetic anisotropy (PMA) and high Curie temperature above room-temperature. Moreover, the present M2XS2Se2 monolayers hold sizable nontrivial topological gaps, resulting in the 1st chiral edge state with Chern number C=-1. Unexpectedly, there also exists an occupied 2nd chiral edge state below the Fermi level. Although all M2XS2Se2 monolayers remain the characteristic of PMA by applying the biaxial strain, various topological phase transitions are present. V2WS2Se2 monolayer preserves the QAH state regardless of strain, while the V2MoS2Se2 and Ti2WS2Se2 monolayers transform from QAH states to metallic states under the tensile strains. The present M2XS2Se2 monolayers show the competitive advantages among the reported materials for the development of topological electronic devices.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452024","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}
Simon U. Okafor, Gabriele Pinto, Michael Brdecka, William Smith, Tucker Lewis, Michael Gutierrez, Darrin Bellert
Quantum mechanical tunneling (QMT) is a well-documented phenomenon in the C-H bond activation mechanism and is commonly identified by large KIE values. Herein we present surprising findings in the kinetic study of hydrogen tunneling in the Co+ mediated decomposition of acetic acid and its perdeuterated isotopologue, conducted with the energy resolved Single Photon Initiated Dissociative Rearrangement Reaction (SPIDRR) technique. Following laser activation, the reaction proceeds along parallel product channels Co(CH4O)++CO and Co(C2H2O)++H2O. An energetic threshold is observed in the energy dependence of the unimolecular microcanonical rate constants, k(E). This is interpreted as the reacting population surmounting a rate-limiting Eyring barrier in the reaction’s potential energy surface. Measurements of the heavier isotopologue’s reaction kinetics supports this interpretation. Kinetic signatures measured at energies below the Eyring barrier are attributed to H/D QMT. The below-the-barrier tunneling kinetics presents an unusually linear energy dependence and a staggeringly small tunneling KIE of ~1.4 over a wide energy range. We explain this surprising observation in terms of a narrow tunneling barrier, wherein the electronic structure of the Co+ metal plays a pivotal role in enhanced reactivity by promoting efficient tunneling. These results suggest that hydrogen tunneling could play important functions in transition metal chemistry, such as that found in enzymatic mechanisms, even if small KIE values are measured.
量子力学隧道（QMT）是 C-H 键活化机制中的一种有据可查的现象，通常通过较大的 KIE 值来识别。在此，我们利用能量分辨单光子引发的歧化重排反应（SPIDRR）技术，对 Co+介导的乙酸及其氚化异构体分解过程中的氢隧道现象进行了动力学研究，并提出了令人惊讶的发现。激光激活后，反应沿着平行的产物通道 Co(CH4O)++CO 和 Co(C2H2O)++H2O进行。从单分子微观经典速率常数 k(E) 的能量依赖性中可以观察到一个能量阈值。这被解释为反应物种群克服了反应势能面上的限速艾林障碍。对较重同位素反应动力学的测量支持这一解释。在能量低于艾林势垒时测得的动力学特征归因于 H/D QMT。低于势垒的隧穿动力学呈现出不同寻常的线性能量依赖性，在很宽的能量范围内，隧穿 KIE 小得惊人，约为 1.4。我们从窄隧道势垒的角度解释了这一令人惊讶的现象，其中 Co+ 金属的电子结构通过促进有效的隧道作用，在增强反应活性方面发挥了关键作用。这些结果表明，即使测得的 KIE 值较小，氢隧道也能在过渡金属化学中发挥重要作用，例如在酶机理中发现的作用。
{"title":"Hydrogen Tunneling with an Atypically Small KIE Measured in the Mediated Decomposition of the Co(CH3COOH)+ Complex","authors":"Simon U. Okafor, Gabriele Pinto, Michael Brdecka, William Smith, Tucker Lewis, Michael Gutierrez, Darrin Bellert","doi":"10.1039/d4cp02722a","DOIUrl":"https://doi.org/10.1039/d4cp02722a","url":null,"abstract":"Quantum mechanical tunneling (QMT) is a well-documented phenomenon in the C-H bond activation mechanism and is commonly identified by large KIE values. Herein we present surprising findings in the kinetic study of hydrogen tunneling in the Co<small><sup>+</sup></small> mediated decomposition of acetic acid and its perdeuterated isotopologue, conducted with the energy resolved Single Photon Initiated Dissociative Rearrangement Reaction (SPIDRR) technique. Following laser activation, the reaction proceeds along parallel product channels Co(CH<small><sub>4</sub></small>O)<small><sup>+</sup></small>+CO and Co(C<small><sub>2</sub></small>H<small><sub>2</sub></small>O)<small><sup>+</sup></small>+H<small><sub>2</sub></small>O. An energetic threshold is observed in the energy dependence of the unimolecular microcanonical rate constants, k(E). This is interpreted as the reacting population surmounting a rate-limiting Eyring barrier in the reaction’s potential energy surface. Measurements of the heavier isotopologue’s reaction kinetics supports this interpretation. Kinetic signatures measured at energies below the Eyring barrier are attributed to H/D QMT. The below-the-barrier tunneling kinetics presents an unusually linear energy dependence and a staggeringly small tunneling KIE of ~1.4 over a wide energy range. We explain this surprising observation in terms of a narrow tunneling barrier, wherein the electronic structure of the Co<small><sup>+</sup></small> metal plays a pivotal role in enhanced reactivity by promoting efficient tunneling. These results suggest that hydrogen tunneling could play important functions in transition metal chemistry, such as that found in enzymatic mechanisms, even if small KIE values are measured.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142487036","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}
Deep eutectic solvents (DESs) are considered as designer solvents which serve as an alternative to traditional solvents. Numerous favourable properties and advantageous characteristics promote their utility in bio-catalysis. Therefore, these have emerged as attractive sustainable media for different biomacromolecules. In the present work, we have synthesized cholinium- based DESs having molar ratio of hydrogen bond acceptor (HBA): hydrogen bond donor (HBD) in 1:2 by varying the cationic ratio in HBA forming the DESs as monocholinium citrate ([Chn][Cit]), dicholinium citrate ([Chn]2[Cit]) and tricholinium citrate ([Chn]3[Cit]), keeping HBD constant as ethylene glycol (EG) to study their suitability for α-chymotrypsin (α-CT). Herein, we have systematically evaluated the influence of DES-1 ([Chn][Cit])-[EG]), DES-2 ([Chn]2[Cit])-[EG]) and DES-3 ([Chn]3[Cit])-[EG]) on structural and thermal stability, thermodynamic profile, colloidal stability and enzymatic activity of α-CT using different spectroscopic techniques. The spectroscopic results explicitly elucidate enhanced structural stability and activity of enzyme as the cationic ratio on HBA increases. Fascinatingly, temperature-dependent studies through both fluorescence and activity measurements supported that DES-2 and DES-3 have highly beneficial effects on α-CT stability. The transition temperature (Tm) of α-CT was augmented by 12 °C in DES-2, 10 °C in DES-3 and 9.1 °C in DES-1 when compared to the enzyme in buffer. Furthermore, transmission electron microscopy (TEM) analysis revealed that the morphology of α-CT in DES-2 and DES-3 closely mirrored the structure of α-CT, while DES-1 exhibited only minor structural deviations. These findings were corroborated by hydrodynamic size (dH) measurements and average decay time analysis, which confirmed the observed morphological similarities and perturbations. The long-term preservation ability and kinetics of DES-3 was eventually confirmed by Michaelis-Menten kinetics. Ultimately, these outcomes demonstrate that by increasing the molar ratio of cholinium cation in HBA can lead to intensify the proficiency of DESs to stabilize the α-CT structure. Our results also suggest that the effect imparted by DESs was due to DES itself rather than its composing elements. Also, how the biocompatibility of DESs towards enzymes can be varied by changing molar ratios of the constituent components of DESs to facilitate the expansion of applicability of DESs in biocatalysis.
{"title":"Unravelling the stabilization mechanism of mono-, di and tri-cholinium citrate-ethylene glycol DESs towards α-chymotrypsin for preservation and activation of the enzyme","authors":"Bindu Yadav, Niketa Yadav, Pannuru Venkatesu","doi":"10.1039/d4cp03315a","DOIUrl":"https://doi.org/10.1039/d4cp03315a","url":null,"abstract":"Deep eutectic solvents (DESs) are considered as designer solvents which serve as an alternative to traditional solvents. Numerous favourable properties and advantageous characteristics promote their utility in bio-catalysis. Therefore, these have emerged as attractive sustainable media for different biomacromolecules. In the present work, we have synthesized cholinium- based DESs having molar ratio of hydrogen bond acceptor (HBA): hydrogen bond donor (HBD) in 1:2 by varying the cationic ratio in HBA forming the DESs as monocholinium citrate ([Chn][Cit]), dicholinium citrate ([Chn]2[Cit]) and tricholinium citrate ([Chn]3[Cit]), keeping HBD constant as ethylene glycol (EG) to study their suitability for α-chymotrypsin (α-CT). Herein, we have systematically evaluated the influence of DES-1 ([Chn][Cit])-[EG]), DES-2 ([Chn]2[Cit])-[EG]) and DES-3 ([Chn]3[Cit])-[EG]) on structural and thermal stability, thermodynamic profile, colloidal stability and enzymatic activity of α-CT using different spectroscopic techniques. The spectroscopic results explicitly elucidate enhanced structural stability and activity of enzyme as the cationic ratio on HBA increases. Fascinatingly, temperature-dependent studies through both fluorescence and activity measurements supported that DES-2 and DES-3 have highly beneficial effects on α-CT stability. The transition temperature (Tm) of α-CT was augmented by 12 °C in DES-2, 10 °C in DES-3 and 9.1 °C in DES-1 when compared to the enzyme in buffer. Furthermore, transmission electron microscopy (TEM) analysis revealed that the morphology of α-CT in DES-2 and DES-3 closely mirrored the structure of α-CT, while DES-1 exhibited only minor structural deviations. These findings were corroborated by hydrodynamic size (dH) measurements and average decay time analysis, which confirmed the observed morphological similarities and perturbations. The long-term preservation ability and kinetics of DES-3 was eventually confirmed by Michaelis-Menten kinetics. Ultimately, these outcomes demonstrate that by increasing the molar ratio of cholinium cation in HBA can lead to intensify the proficiency of DESs to stabilize the α-CT structure. Our results also suggest that the effect imparted by DESs was due to DES itself rather than its composing elements. Also, how the biocompatibility of DESs towards enzymes can be varied by changing molar ratios of the constituent components of DESs to facilitate the expansion of applicability of DESs in biocatalysis.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486293","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}
Aromatic boron-containing organic compound C2B2H2 with an unusual C=C bond was experimentally synthesized in 2017. Here we investigate the structure and bonding nature of C2B2H2 and its derivatives C2B2R2 using DFT and VB theory. While the C=C bond in C2B2R2 consists of a π bond and a charge-shift (CS) bond, C2B2F2 has the lowest LUMO energy and its LUMO is similar with that of ethylene, suggesting that C2B2F2 can be an ideal dienophile for the Diels-Alder reaction. Subsequently, the mechanism and stereoselectivity of the Diels-Alder reaction of C2B2F2 with 5-substituted cyclopentadienes are studied. Computations demonstrate that these Diels-Alder reactions are feasible thermodynamically and kinetically. The stereoselectivity and distortion angles of C2B2R2 exhibit linear correlations with the electronegativity difference between the two substituents bonded to the C(sp3) of cyclopentadiene, suggesting that the stereoselectivity of related Diels-Alder reaction products can be modulated by the substitution of cyclopentadiene. Considering the current interests in boron neutron capture therapy (BNCT), we design six BNCT drugs through the Diels-Alder reaction of C2B2F2 with dienes containing peptide fragments. Thus, we demonstrate a kind of new method of designing three-in-one BNCT drugs with the facile Diels-Alder reaction.
{"title":"Double-Boron Heterocyclic Carbenes: Computational Study of the Diels-Alder Reactions","authors":"Changyu Cao, Congjie Zhang, Junjing Gu, Yirong Mo","doi":"10.1039/d4cp03615h","DOIUrl":"https://doi.org/10.1039/d4cp03615h","url":null,"abstract":"Aromatic boron-containing organic compound C<small><sub>2</sub></small>B<small><sub>2</sub></small>H<small><sub>2</sub></small> with an unusual C=C bond was experimentally synthesized in 2017. Here we investigate the structure and bonding nature of C<small><sub>2</sub></small>B<small><sub>2</sub></small>H<small><sub>2</sub></small> and its derivatives C<small><sub>2</sub></small>B<small><sub>2</sub></small>R<small><sub>2</sub></small> using DFT and VB theory. While the C=C bond in C<small><sub>2</sub></small>B<small><sub>2</sub></small>R<small><sub>2</sub></small> consists of a π bond and a charge-shift (CS) bond, C<small><sub>2</sub></small>B<small><sub>2</sub></small>F<small><sub>2</sub></small> has the lowest LUMO energy and its LUMO is similar with that of ethylene, suggesting that C<small><sub>2</sub></small>B<small><sub>2</sub></small>F<small><sub>2</sub></small> can be an ideal dienophile for the Diels-Alder reaction. Subsequently, the mechanism and stereoselectivity of the Diels-Alder reaction of C<small><sub>2</sub></small>B<small><sub>2</sub></small>F<small><sub>2</sub></small> with 5-substituted cyclopentadienes are studied. Computations demonstrate that these Diels-Alder reactions are feasible thermodynamically and kinetically. The stereoselectivity and distortion angles of C<small><sub>2</sub></small>B<small><sub>2</sub></small>R<small><sub>2</sub></small> exhibit linear correlations with the electronegativity difference between the two substituents bonded to the C(sp<small><sup>3</sup></small>) of cyclopentadiene, suggesting that the stereoselectivity of related Diels-Alder reaction products can be modulated by the substitution of cyclopentadiene. Considering the current interests in boron neutron capture therapy (BNCT), we design six BNCT drugs through the Diels-Alder reaction of C<small><sub>2</sub></small>B<small><sub>2</sub></small>F<small><sub>2</sub></small> with dienes containing peptide fragments. Thus, we demonstrate a kind of new method of designing three-in-one BNCT drugs with the facile Diels-Alder reaction.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142486284","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}
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