Giovanni Rodrigues Morselli, Frederik Philippi, Pedro Henrique Sabanay, R Bazito, Margarida Costa Gomes, Rômulo Augusto Ando
The DBU-CO2 adduct was characterized for the first time by 13C NMR with labelled 13CO2 and IR spectroscopy. Theoretical calculations were crucial to determine that the adduct is stable in ionic liquid medium in the presence of water. These findings provide new insights into superbase-CO2 interactions, unveiling a new potential route to CO2 activation.
{"title":"Is the DBU-CO2 Adduct Stable in Ionic Liquid Media?","authors":"Giovanni Rodrigues Morselli, Frederik Philippi, Pedro Henrique Sabanay, R Bazito, Margarida Costa Gomes, Rômulo Augusto Ando","doi":"10.1039/d5cp00899a","DOIUrl":"https://doi.org/10.1039/d5cp00899a","url":null,"abstract":"The DBU-CO<small><sub>2</sub></small> adduct was characterized for the first time by <small><sup>13</sup></small>C NMR with labelled <small><sup>13</sup></small>CO<small><sub>2</sub></small> and IR spectroscopy. Theoretical calculations were crucial to determine that the adduct is stable in ionic liquid medium in the presence of water. These findings provide new insights into superbase-CO<small><sub>2</sub></small> interactions, unveiling a new potential route to CO<small><sub>2</sub></small> activation.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"23 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143832372","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}
Aline De Souza Bozzi, Rita de Cássia Oliveira Sebastião, Willian R. Rocha
In this work, we have proposed and evaluated a first-order kinetic model to describe the excitedstates dynamics of molecules as a computationally cheaper alternative to describe and understand the photophysical profile of large systems. The method is based on calculating the radiative and nonradiative rate constants of all photophysical processes of a collection of crucial low-lying excited states and modeling the decay over time using a first-order kinetic model. We have successfully applied the method to the [Ru(bpz)3]2+ (bpz = 2,2’-bipyrazyl) complex as a case study, obtaining good results. By employing this first-order kinetic model, it is possible to simulate the time-dependent decay process and the evolution of the excited-state population, revealing not only the primary deactivation pathway but also secondary states that contribute to the overall decay mechanism, highlighting alternative channels that may lead to photochemical side products. This approach provides a computationally efficient yet accurate method for studying more intricate systems relevant to photoinduced processes. It enhances the understanding of these compounds and offers guidance for fine-tuning their chemical and structural properties for targeted applications.
{"title":"Understanding the Excited State Decay Mechanism of Complex Systems: A General First-Order Kinetic Model","authors":"Aline De Souza Bozzi, Rita de Cássia Oliveira Sebastião, Willian R. Rocha","doi":"10.1039/d5cp00606f","DOIUrl":"https://doi.org/10.1039/d5cp00606f","url":null,"abstract":"In this work, we have proposed and evaluated a first-order kinetic model to describe the excitedstates dynamics of molecules as a computationally cheaper alternative to describe and understand the photophysical profile of large systems. The method is based on calculating the radiative and nonradiative rate constants of all photophysical processes of a collection of crucial low-lying excited states and modeling the decay over time using a first-order kinetic model. We have successfully applied the method to the [Ru(bpz)3]2+ (bpz = 2,2’-bipyrazyl) complex as a case study, obtaining good results. By employing this first-order kinetic model, it is possible to simulate the time-dependent decay process and the evolution of the excited-state population, revealing not only the primary deactivation pathway but also secondary states that contribute to the overall decay mechanism, highlighting alternative channels that may lead to photochemical side products. This approach provides a computationally efficient yet accurate method for studying more intricate systems relevant to photoinduced processes. It enhances the understanding of these compounds and offers guidance for fine-tuning their chemical and structural properties for targeted applications.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"50 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143837396","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}
Xiao-Meng Huang, Zhi-Wen Ji, Xun-Lei Ding, Yan Chen, Wei Li, Jiao-Jiao Chen, Shao-Peng Xu, Lin-Lin Li
DFT calculations were utilized to explore the electrocatalytic nitrogen reduction reaction (NRR) mechanisms catalyzed by trimetallic clusters M3 (M = Ti, Zr, V, and Nb), both unsupported and supported by bowl-shaped sumanene. The substrate enhanced N2 adsorption and activation but hindered hydrogenation due to more negative adsorption energies. The substrate promoted hydrogenation on nitrogen, reducing the interference of the hydrogen evolution reaction (HER) and enhancing the NRR selectivity. Three fundamental and three mixed pathways were investigated, and the rate-determining step (RDS) was identified for each pathway. Both through a consecutive pathway, V3 exhibits the best catalytic performance with the free energy change of the RDS (ΔGRDS) as 0.82 eV, while the optimal supported catalyst, Nb3 supported on sumanene, has a ΔGRDS of 1.43 eV. The introduction of the substrate generally increased ΔGRDS by 0.3-0.8 eV. The substrate can effectively regulate the distance between metal atoms and reduce the change in geometric structures of M3 clusters during the reaction process, thereby enhancing the structural stability of the active sites in the NRR process. The substrate can reduce the reactivity differences among catalysts with different metal types. This so-called blurring effect allows cheap metals to partially replace noble metals while maintaining catalyst performance. A linear correlation between charge changes on M3 or M3 together with the substrate and ΔG was observed, providing a potential method for optimizing the catalyst performance and designing new catalysts.
{"title":"Theoretical Study on Catalytic Ammonia Synthesis by Trimetallic Clusters with or without Sumanene Support","authors":"Xiao-Meng Huang, Zhi-Wen Ji, Xun-Lei Ding, Yan Chen, Wei Li, Jiao-Jiao Chen, Shao-Peng Xu, Lin-Lin Li","doi":"10.1039/d5cp00926j","DOIUrl":"https://doi.org/10.1039/d5cp00926j","url":null,"abstract":"DFT calculations were utilized to explore the electrocatalytic nitrogen reduction reaction (NRR) mechanisms catalyzed by trimetallic clusters M<small><sub>3</sub></small> (M = Ti, Zr, V, and Nb), both unsupported and supported by bowl-shaped sumanene. The substrate enhanced N<small><sub>2</sub></small> adsorption and activation but hindered hydrogenation due to more negative adsorption energies. The substrate promoted hydrogenation on nitrogen, reducing the interference of the hydrogen evolution reaction (HER) and enhancing the NRR selectivity. Three fundamental and three mixed pathways were investigated, and the rate-determining step (RDS) was identified for each pathway. Both through a consecutive pathway, V<small><sub>3</sub></small> exhibits the best catalytic performance with the free energy change of the RDS (Δ<em>G</em><small><sub>RDS</sub></small>) as 0.82 eV, while the optimal supported catalyst, Nb<small><sub>3</sub></small> supported on sumanene, has a Δ<em>G</em><small><sub>RDS</sub></small> of 1.43 eV. The introduction of the substrate generally increased Δ<em>G</em><small><sub>RDS</sub></small> by 0.3-0.8 eV. The substrate can effectively regulate the distance between metal atoms and reduce the change in geometric structures of M<small><sub>3</sub></small> clusters during the reaction process, thereby enhancing the structural stability of the active sites in the NRR process. The substrate can reduce the reactivity differences among catalysts with different metal types. This so-called blurring effect allows cheap metals to partially replace noble metals while maintaining catalyst performance. A linear correlation between charge changes on M<small><sub>3</sub></small> or M<small><sub>3</sub></small> together with the substrate and Δ<em>G</em> was observed, providing a potential method for optimizing the catalyst performance and designing new catalysts.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"108 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827480","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}
Paul David Lane, Katya E Moncrieff, Stuart Greaves, Kenneth G McKendrick, Matthew L Costen
Collisions of ground-electronic-state CN radicals with the surface of a prototypical saturated-hydrocarbon liquid have been studied experimentally. A molecular beam of CN(X2Σ+) with a mean laboratory-frame kinetic energy of 44 kJ mol-1 was directed at normal incidence at a continually refreshed liquid squalane (2,6,10,15,19,23-hexamethyltetracosane) surface. The incident and scattered CN radicals were detected in a range of rotational states by multi-pass frequency-modulated absorption spectroscopy on selected lines of the CN(A-X) transition. The ratio of scattered-to-incident CN populations for squalane were compared with those obtained previously for a reference liquid, perfluoropolyether (PFPE), which is assumed to be inert. The overall survival probability, summed over the significantly populated rotational levels, of CN on squalane was found to be 0.15 ± 0.04. The 85% that is lost is inferred, on energetic grounds, to produce HCN via H-atom abstraction. The surviving CN has a significantly superthermal rotational distribution and a hot, non-thermal velocity distribution in the direction perpendicular to the surface normal. These dynamical attributes are characteristic of impulsive scattering. However, we conclude that the low survival probability is not compatible with a simple, ‘single-bounce’ mechanism and hence that multiple-encounter trajectories must contribute significantly to CN reactive loss. We find no evidence of a distinct trapping-desorption component, corresponding to full thermal accommodation, in the surviving CN from either squalane or PFPE at these collision energies.
{"title":"Reactive Uptake via Inelastic Scattering of CN Radicals at a Liquid Hydrocarbon Surface","authors":"Paul David Lane, Katya E Moncrieff, Stuart Greaves, Kenneth G McKendrick, Matthew L Costen","doi":"10.1039/d5cp00406c","DOIUrl":"https://doi.org/10.1039/d5cp00406c","url":null,"abstract":"Collisions of ground-electronic-state CN radicals with the surface of a prototypical saturated-hydrocarbon liquid have been studied experimentally. A molecular beam of CN(X<small><sup>2</sup></small>Σ<small><sup>+</sup></small>) with a mean laboratory-frame kinetic energy of 44 kJ mol<small><sup>-1</sup></small> was directed at normal incidence at a continually refreshed liquid squalane (2,6,10,15,19,23-hexamethyltetracosane) surface. The incident and scattered CN radicals were detected in a range of rotational states by multi-pass frequency-modulated absorption spectroscopy on selected lines of the CN(A-X) transition. The ratio of scattered-to-incident CN populations for squalane were compared with those obtained previously for a reference liquid, perfluoropolyether (PFPE), which is assumed to be inert. The overall survival probability, summed over the significantly populated rotational levels, of CN on squalane was found to be 0.15 ± 0.04. The 85% that is lost is inferred, on energetic grounds, to produce HCN via H-atom abstraction. The surviving CN has a significantly superthermal rotational distribution and a hot, non-thermal velocity distribution in the direction perpendicular to the surface normal. These dynamical attributes are characteristic of impulsive scattering. However, we conclude that the low survival probability is not compatible with a simple, ‘single-bounce’ mechanism and hence that multiple-encounter trajectories must contribute significantly to CN reactive loss. We find no evidence of a distinct trapping-desorption component, corresponding to full thermal accommodation, in the surviving CN from either squalane or PFPE at these collision energies.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"119 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827478","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}
As an emerging photovoltaic technology, perovskite solar cells (PSCs) have become a research hotspot due to their excellent photoelectric conversion efficiency (PCE) and low-cost manufacturing process. Enhancing the crystallization quality of perovskite films and mitigating defects through material engineering is crucial for improving the performance of PSCs. In this study, a naturally occurring amino acid, DL-Methionine, is incorporated as an additive to enhance the crystallization quality and passivate defects in perovskite films. The results show that the appropriate concentration of DL-Methionine additive can not only improve the crystallization kinetics of perovskite but also reduce the defects of perovskite films through its coordination with perovskite ions, thereby reducing defect-assisted recombination. Finally, the optimized PSCs based on the DL-Methionine additive obtained the highest power conversion efficiency of 24.72%, significantly higher than those without the DL-Methionine additive (21.83%). Moreover, the stability of PSCs is significantly improved with the DL-Methionine additive. This work demonstrates the potential of DL-Methionine as an effective passivation agent for high-efficiency and stable PSCs.
{"title":"High-Efficiency and Stable Perovskite Solar Cells via DL-Methionine-Enhanced Crystallization and Defect Passivation","authors":"Xiaolan Li, Yanwei Xu, Fuxing Chen, Dongxing Lu, Yajun Zhu, Cong Li","doi":"10.1039/d4cp04698f","DOIUrl":"https://doi.org/10.1039/d4cp04698f","url":null,"abstract":"As an emerging photovoltaic technology, perovskite solar cells (PSCs) have become a research hotspot due to their excellent photoelectric conversion efficiency (PCE) and low-cost manufacturing process. Enhancing the crystallization quality of perovskite films and mitigating defects through material engineering is crucial for improving the performance of PSCs. In this study, a naturally occurring amino acid, DL-Methionine, is incorporated as an additive to enhance the crystallization quality and passivate defects in perovskite films. The results show that the appropriate concentration of DL-Methionine additive can not only improve the crystallization kinetics of perovskite but also reduce the defects of perovskite films through its coordination with perovskite ions, thereby reducing defect-assisted recombination. Finally, the optimized PSCs based on the DL-Methionine additive obtained the highest power conversion efficiency of 24.72%, significantly higher than those without the DL-Methionine additive (21.83%). Moreover, the stability of PSCs is significantly improved with the DL-Methionine additive. This work demonstrates the potential of DL-Methionine as an effective passivation agent for high-efficiency and stable PSCs.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"21 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827350","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}
Anam Fatima, Eleanor K Ashworth, Isabelle Fernandes, A. N. Cammidge, Giovanni Bressan, Steve R. Meech, James N Bull
Incorporation of fluorescent proteins (FPs) into biological systems has revolutionised bioimaging and the understanding of cellular processes. Ongoing developments of FPs are driving efforts to characterise the fundamental photoactive unit (chromophore) embedded within the protein. Cyan FP has a blue emitting chromophore and is widely used in Forster resonance energy transfer studies. Here, we probe the ultrafast photophysics of the cyan FP chromophore in solution using time resolvedfluorescence up-conversion and transient absorption spectroscopies. The ultrafast dynamics are characterised by two lifetimes, sub-picosecond τ1 (or τF) associated with loss of the fluorescent Franck-Condon state, and lifetime τ2 on the order of several picoseconds that is linked with cooling of a hot ground state. MRSF-TDDFT calculations show that the relaxed S1 state equilibrium geometry is classified as a partial twisted intramolecular charge-transfer state, and lies close in energy to a conical intersection seam associated with torsion about the central double bond leading to facile internal conversion. The excited state dynamics exhibit only a weak viscosity dependence, consistent with a barrierless and near-volume-conserving non-radiative decay mechanism. Fluorescence lifetimes for the deprotonated anion are twice those for the neutral.
{"title":"Ultrafast photophysics of the cyan fluorescent protein chromophore in solution","authors":"Anam Fatima, Eleanor K Ashworth, Isabelle Fernandes, A. N. Cammidge, Giovanni Bressan, Steve R. Meech, James N Bull","doi":"10.1039/d5cp00942a","DOIUrl":"https://doi.org/10.1039/d5cp00942a","url":null,"abstract":"Incorporation of fluorescent proteins (FPs) into biological systems has revolutionised bioimaging and the understanding of cellular processes. Ongoing developments of FPs are driving efforts to characterise the fundamental photoactive unit (chromophore) embedded within the protein. Cyan FP has a blue emitting chromophore and is widely used in Forster resonance energy transfer studies. Here, we probe the ultrafast photophysics of the cyan FP chromophore in solution using time resolvedfluorescence up-conversion and transient absorption spectroscopies. The ultrafast dynamics are characterised by two lifetimes, sub-picosecond τ<small><sub>1</sub></small> (or τ<small><sub>F</sub></small>) associated with loss of the fluorescent Franck-Condon state, and lifetime τ<small><sub>2</sub></small> on the order of several picoseconds that is linked with cooling of a hot ground state. MRSF-TDDFT calculations show that the relaxed S<small><sub>1</sub></small> state equilibrium geometry is classified as a partial twisted intramolecular charge-transfer state, and lies close in energy to a conical intersection seam associated with torsion about the central double bond leading to facile internal conversion. The excited state dynamics exhibit only a weak viscosity dependence, consistent with a barrierless and near-volume-conserving non-radiative decay mechanism. Fluorescence lifetimes for the deprotonated anion are twice those for the neutral.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"34 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827479","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}
Mevlut Dogan, Wania Wolff, Deepthy Maria Mootheril, Thomas Pfeifer, Alexander Dorn
The absolute total and partial ionization cross sections resulting from electron collisions with fluorinated molecules CF4 and CHF3 were obtained by recoil-ion momentum spectroscopy with full acceptance for energetic ionic fragments. For absolute normalization the relative-flow technique was applied. The cross sections for single and double ionization as well as for dissociation were measured for electron energies from 20 eV to 1 keV. The data are compared with previous experiments and model calculations. The dissociation channel-specific differences between CF4 and CHF3 are discussed. The present data are relevant for the evaluation of the electron interaction on these potent greenhouse gases with a high global warming potential in the Earth biosphere and in plasma and other industrial applications.
{"title":"Electron impact single and double ionization and dissociation: revisiting CF4 and CHF3 with an improved experimental method","authors":"Mevlut Dogan, Wania Wolff, Deepthy Maria Mootheril, Thomas Pfeifer, Alexander Dorn","doi":"10.1039/d5cp00746a","DOIUrl":"https://doi.org/10.1039/d5cp00746a","url":null,"abstract":"The absolute total and partial ionization cross sections resulting from electron collisions with fluorinated molecules CF<small><sub>4</sub></small> and CHF<small><sub>3</sub></small> were obtained by recoil-ion momentum spectroscopy with full acceptance for energetic ionic fragments. For absolute normalization the relative-flow technique was applied. The cross sections for single and double ionization as well as for dissociation were measured for electron energies from 20 eV to 1 keV. The data are compared with previous experiments and model calculations. The dissociation channel-specific differences between CF<small><sub>4</sub></small> and CHF<small><sub>3</sub></small> are discussed. The present data are relevant for the evaluation of the electron interaction on these potent greenhouse gases with a high global warming potential in the Earth biosphere and in plasma and other industrial applications.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"6 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143827481","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}
Gang Fu, Hongyi Wang, Wenqing Zhen, Xin Zhou, Li Yang, Jiaxu Zhang
The competition between base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) reactions and their intrinsic reactivity is a hot issue in organic chemistry research. To investigate the influence factors of E2/SN2 channel selectivity, the HO− + CH3CH2Br reaction is performed utilizing direct dynamics simulations and unravel how nucleophile and leaving group modulates the microscopic mechanisms for the X− (X = F, HO) + CH3CH2Y (Y = Cl, Br) reactions. Our simulations show a significant increase in the direct mechanism branching ratio from 0.41 to 0.62 when the nucleophile changes from F− to HO−. This mechanism shift is driven by the entrance channel complex's geometric configuration and the ionic-molecular intermediate's lifetime. The disappearance of hydrogen-bonded complexes suppresses prolonged interactions of prereaction complex, with more than half of the trajectories separating into products directly after the first collision. When the leaving group changes from Cl to Br, although the anti-E2 channel still dominates for the HO− + CH3CH2Br reaction, its decreased proportion indicates that SN2 is more competitive. This result is attributed to the decrease in the bmax value in the HO− + CH3CH2Br reaction, which diminishes the role of the direct stripping mechanism at large collision parameters and ultimately decreases the probability of the anti-E2 reaction. This study underscores the impact of nucleophiles and leaving groups on the dynamics of E2/SN2 competition and its microscopic mechanisms, providing valuable insights into reaction selectivity in complex chemical environments and systems.
{"title":"Competitive Dynamics of Elimination and Substitution Reaction Modulated by Nucleophile and Leaving Group","authors":"Gang Fu, Hongyi Wang, Wenqing Zhen, Xin Zhou, Li Yang, Jiaxu Zhang","doi":"10.1039/d4cp04752d","DOIUrl":"https://doi.org/10.1039/d4cp04752d","url":null,"abstract":"The competition between base-induced elimination (E2) and bimolecular nucleophilic substitution (SN2) reactions and their intrinsic reactivity is a hot issue in organic chemistry research. To investigate the influence factors of E2/SN2 channel selectivity, the HO− + CH3CH2Br reaction is performed utilizing direct dynamics simulations and unravel how nucleophile and leaving group modulates the microscopic mechanisms for the X− (X = F, HO) + CH3CH2Y (Y = Cl, Br) reactions. Our simulations show a significant increase in the direct mechanism branching ratio from 0.41 to 0.62 when the nucleophile changes from F− to HO−. This mechanism shift is driven by the entrance channel complex's geometric configuration and the ionic-molecular intermediate's lifetime. The disappearance of hydrogen-bonded complexes suppresses prolonged interactions of prereaction complex, with more than half of the trajectories separating into products directly after the first collision. When the leaving group changes from Cl to Br, although the anti-E2 channel still dominates for the HO− + CH3CH2Br reaction, its decreased proportion indicates that SN2 is more competitive. This result is attributed to the decrease in the bmax value in the HO− + CH3CH2Br reaction, which diminishes the role of the direct stripping mechanism at large collision parameters and ultimately decreases the probability of the anti-E2 reaction. This study underscores the impact of nucleophiles and leaving groups on the dynamics of E2/SN2 competition and its microscopic mechanisms, providing valuable insights into reaction selectivity in complex chemical environments and systems.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"66 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143822409","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}
Huan Liu, Xinyue Yan, Xinyue He, Zhanhui Peng, Di Wu, Pengfei Liang, Lingling Wei, Xiaolian Chao, Zupei Yang
The considerable demand for energy and the accelerated growth of the microelectronics sector has prompted extensive research into dielectric materials with high dielectric constants for use in electronic storage devices. In this study, a conventional solid-phase method was used to enhance the dielectric properties of CdCu3Ti4O12 by co-doping Ti sites with Tb and Ta ions. Impressively, the CdCu3(Tb1/2Ta1/2)xTi4−xO12 ceramics exhibit superior dielectric properties with a dielectric constant (ε ∼ 3.21 × 104) and a low loss tangent (tan δ ∼ 0.020) at 1 kHz. In addition, the temperature dependent-coefficient of variation of its dielectric constant (Δε/ε25 °C) is less than ±15% over the temperature range of −13 to 174 °C. The dielectric response is mainly due to intrinsic and extrinsic effects, and the inherent effects may be due to the formation of defect clusters (i.e., , and ). While the non-intrinsic effects are caused by the microstructure of the internal barrier layer capacitor, the impedance spectra show the presence of semiconductor grains as well as the huge resistance at the grain boundaries, where the heterogeneous structure causes an increase in grain boundary resistance. This study explores the dielectric response of a new type of giant dielectric ceramics and provides a new candidate for the fabrication of ceramic capacitors.
{"title":"Mixed valence that induces superior dielectric properties of CdCu3(Tb1/2Ta1/2)xTi4−xO12 ceramics","authors":"Huan Liu, Xinyue Yan, Xinyue He, Zhanhui Peng, Di Wu, Pengfei Liang, Lingling Wei, Xiaolian Chao, Zupei Yang","doi":"10.1039/d5cp00195a","DOIUrl":"https://doi.org/10.1039/d5cp00195a","url":null,"abstract":"The considerable demand for energy and the accelerated growth of the microelectronics sector has prompted extensive research into dielectric materials with high dielectric constants for use in electronic storage devices. In this study, a conventional solid-phase method was used to enhance the dielectric properties of CdCu<small><sub>3</sub></small>Ti<small><sub>4</sub></small>O<small><sub>12</sub></small> by co-doping Ti sites with Tb and Ta ions. Impressively, the CdCu<small><sub>3</sub></small>(Tb<small><sub>1/2</sub></small>Ta<small><sub>1/2</sub></small>)<small><sub><em>x</em></sub></small>Ti<small><sub>4−<em>x</em></sub></small>O<small><sub>12</sub></small> ceramics exhibit superior dielectric properties with a dielectric constant (<em>ε</em> ∼ 3.21 × 10<small><sup>4</sup></small>) and a low loss tangent (tan <em>δ</em> ∼ 0.020) at 1 kHz. In addition, the temperature dependent-coefficient of variation of its dielectric constant (Δ<em>ε</em>/<em>ε</em><small><sub>25 °C</sub></small>) is less than ±15% over the temperature range of −13 to 174 °C. The dielectric response is mainly due to intrinsic and extrinsic effects, and the inherent effects may be due to the formation of defect clusters (<em>i.e.</em>, <img align=\"middle\" alt=\"Image ID:d5cp00195a-t1.gif\" src=\"https://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2025/CP/D5CP00195A/d5cp00195a-t1.gif\"/>, <img align=\"middle\" alt=\"Image ID:d5cp00195a-t2.gif\" src=\"https://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2025/CP/D5CP00195A/d5cp00195a-t2.gif\"/> and <img align=\"middle\" alt=\"Image ID:d5cp00195a-t3.gif\" src=\"https://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2025/CP/D5CP00195A/d5cp00195a-t3.gif\"/>). While the non-intrinsic effects are caused by the microstructure of the internal barrier layer capacitor, the impedance spectra show the presence of semiconductor grains as well as the huge resistance at the grain boundaries, where the heterogeneous structure causes an increase in grain boundary resistance. This study explores the dielectric response of a new type of giant dielectric ceramics and provides a new candidate for the fabrication of ceramic capacitors.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"8 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819143","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}
Sebastian Eckert, Laurenz Otto, Eric Johnn Mascarenhas, Annette Pietzsch, Rolf Mitzner, Mattis Fondell, Vinícius Vaz da Cruz, Alexander Föhlisch
In a comparative synchrotron X-ray absorption, non-resonant X-ray emission and resonant inelastic X-ray scattering investigation of the aqueous nitrite and nitrate ions, we access both, their unoccupied and occupied valence electronic structure. Complementary information is gained through the sensitivity to specific orbitals at the nitrogen and the oxygen 1s absorption edges. In particular scattering through the pronounced 1s→ π∗ resonances in combination with the scattering anisotropy and symmetry selection rules allow for an unambiguous assignment of molecular orbitals to their detected spectroscopic fingerprints. The nuclear dynamics in the 1s core-excited states are discussed in the context of the vibrational substructure of the detected spectral lines and signatures of core-excited state symmetry breaking are characterized through an analysis of the excitation energy detuning dependent spectra in combination with the involved potentials. A comparison between TD-DFT based spectrum simulations for isolated molecules and sampled structures from a QM/MM simulation reveal signatures of symmetry breaking induced by the solute-solvent interactions and a different response of spectral signatures of in- and out-of-plane orbitals to the solution environment.
{"title":"Electronic Structure of Aqueous Nitrite and Nitrate Ions from Resonant Inelastic X-ray Scattering","authors":"Sebastian Eckert, Laurenz Otto, Eric Johnn Mascarenhas, Annette Pietzsch, Rolf Mitzner, Mattis Fondell, Vinícius Vaz da Cruz, Alexander Föhlisch","doi":"10.1039/d5cp00748h","DOIUrl":"https://doi.org/10.1039/d5cp00748h","url":null,"abstract":"In a comparative synchrotron X-ray absorption, non-resonant X-ray emission and resonant inelastic X-ray scattering investigation of the aqueous nitrite and nitrate ions, we access both, their unoccupied and occupied valence electronic structure. Complementary information is gained through the sensitivity to specific orbitals at the nitrogen and the oxygen 1s absorption edges. In particular scattering through the pronounced 1s→ π∗ resonances in combination with the scattering anisotropy and symmetry selection rules allow for an unambiguous assignment of molecular orbitals to their detected spectroscopic fingerprints. The nuclear dynamics in the 1s core-excited states are discussed in the context of the vibrational substructure of the detected spectral lines and signatures of core-excited state symmetry breaking are characterized through an analysis of the excitation energy detuning dependent spectra in combination with the involved potentials. A comparison between TD-DFT based spectrum simulations for isolated molecules and sampled structures from a QM/MM simulation reveal signatures of symmetry breaking induced by the solute-solvent interactions and a different response of spectral signatures of in- and out-of-plane orbitals to the solution environment.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"9 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143819140","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}
, 
and 
). While the non-intrinsic effects are caused by the microstructure of the internal barrier layer capacitor, the impedance spectra show the presence of semiconductor grains as well as the huge resistance at the grain boundaries, where the heterogeneous structure causes an increase in grain boundary resistance. This study explores the dielectric response of a new type of giant dielectric ceramics and provides a new candidate for the fabrication of ceramic capacitors.
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