NaNiO2 is a layered material composed of alternating NaO6 and NiO6 octahedra, which undergoes an insulator-metal transition (IMT) from a monoclinic insulating phase to a metallic phase at approximately 480 K. Although this phase transition has been experimentally observed, its microscopic mechanism remains unclear, particularly regarding the role of Jahn-Teller (JT) distortion and the nature of the structural dynamics during the transition. In this work, we carry out a comprehensive first-principles study to address these issues. Our results show that the IMT is primarily driven by the gradual disappearance of the JT distortion of Ni3+, which restores the eg orbital degeneracy and enables electronic delocalization. Furthermore, potential energy surface analysis and phonon spectrum calculations reveal that this process follows a displacive phase transition pathway, consistent with experimental observations. These findings provide, for the first time, a theoretical explanation of the microscopic mechanism underlying the IMT in NaNiO2, thereby clarifying its structural-electronic interplay and offering new insights into the phase transition behavior of transition-metal oxides for future material applications.
{"title":"First-principles investigation of the insulator-metal transition in layered NaNiO<sub>2</sub>: coupled electronic and lattice effects.","authors":"Xiaohong Chu, Zhenyi Jiang, Ping Guo, Jiming Zheng, Xiaodong Zhang","doi":"10.1039/d5cp03746h","DOIUrl":"https://doi.org/10.1039/d5cp03746h","url":null,"abstract":"<p><p>NaNiO<sub>2</sub> is a layered material composed of alternating NaO<sub>6</sub> and NiO<sub>6</sub> octahedra, which undergoes an insulator-metal transition (IMT) from a monoclinic insulating phase to a metallic phase at approximately 480 K. Although this phase transition has been experimentally observed, its microscopic mechanism remains unclear, particularly regarding the role of Jahn-Teller (JT) distortion and the nature of the structural dynamics during the transition. In this work, we carry out a comprehensive first-principles study to address these issues. Our results show that the IMT is primarily driven by the gradual disappearance of the JT distortion of Ni<sup>3+</sup>, which restores the e<sub>g</sub> orbital degeneracy and enables electronic delocalization. Furthermore, potential energy surface analysis and phonon spectrum calculations reveal that this process follows a displacive phase transition pathway, consistent with experimental observations. These findings provide, for the first time, a theoretical explanation of the microscopic mechanism underlying the IMT in NaNiO<sub>2</sub>, thereby clarifying its structural-electronic interplay and offering new insights into the phase transition behavior of transition-metal oxides for future material applications.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049669","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}
Henry Nicole González-Ramírez, Zeferino Gómez-Sandoval, Gururaj Kudur Jayaprakash, Juan Pablo Mojica-Sánchez, Roberto Flores-Moreno, Kayim Pineda-Urbina
In this study, we explored the energetic, structural, and magnetic properties of yttrium-doped lithium and potassium clusters using density functional theory combined with Born–Oppenheimer molecular dynamics simulations. The analysis revealed magnetic superatoms such as K9Y2 (μ = 5μB) with a frontier configuration analogous to Fe+. Global reactivity descriptors, particularly the low hardness values (η), identified K12Y, K11Y2, and K13 as the most reactive potassium clusters, while the analogous Li12Y, Li11Y2, and Li13 were also selected for subsequent hydrogen interaction analyses. The most stable hydrogen–cluster structures extracted from Born–Oppenheimer molecular dynamics at 300 K were reoptimized including dispersion corrections to compute adsorption and Gibbs free energies. The resulting complexes were analyzed through QTAIM, ELF, and Laplacian electron density maps, complemented by CM5 charge analysis. These results reveal predominant molecular physisorption across the Y-doped systems, with localized polarized chemisorption only in Li12Y. Overall, yttrium doping enhances magnetic polarization, energetic stability, and structural resilience of alkali-metal clusters, which retain their superatomic character and near-icosahedral frameworks under hydrogen exposure.
{"title":"Yttrium-doped lithium and potassium clusters: magnetic superatoms and their interaction with hydrogen","authors":"Henry Nicole González-Ramírez, Zeferino Gómez-Sandoval, Gururaj Kudur Jayaprakash, Juan Pablo Mojica-Sánchez, Roberto Flores-Moreno, Kayim Pineda-Urbina","doi":"10.1039/d5cp04393j","DOIUrl":"https://doi.org/10.1039/d5cp04393j","url":null,"abstract":"In this study, we explored the energetic, structural, and magnetic properties of yttrium-doped lithium and potassium clusters using density functional theory combined with Born–Oppenheimer molecular dynamics simulations. The analysis revealed magnetic superatoms such as K<small><sub>9</sub></small>Y<small><sub>2</sub></small> (<em>μ</em> = 5<em>μ</em><small><sub>B</sub></small>) with a frontier configuration analogous to Fe<small><sup>+</sup></small>. Global reactivity descriptors, particularly the low hardness values (<em>η</em>), identified K<small><sub>12</sub></small>Y, K<small><sub>11</sub></small>Y<small><sub>2</sub></small>, and K<small><sub>13</sub></small> as the most reactive potassium clusters, while the analogous Li<small><sub>12</sub></small>Y, Li<small><sub>11</sub></small>Y<small><sub>2</sub></small>, and Li<small><sub>13</sub></small> were also selected for subsequent hydrogen interaction analyses. The most stable hydrogen–cluster structures extracted from Born–Oppenheimer molecular dynamics at 300 K were reoptimized including dispersion corrections to compute adsorption and Gibbs free energies. The resulting complexes were analyzed through QTAIM, ELF, and Laplacian electron density maps, complemented by CM5 charge analysis. These results reveal predominant molecular physisorption across the Y-doped systems, with localized polarized chemisorption only in Li<small><sub>12</sub></small>Y. Overall, yttrium doping enhances magnetic polarization, energetic stability, and structural resilience of alkali-metal clusters, which retain their superatomic character and near-icosahedral frameworks under hydrogen exposure.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"72 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048840","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}
Hayden A Moran, Abigail F. Moody, Mark A Boyer, Paul Garrett, Manuel Quiroz, Sarnali Sanfui, Marcetta Y. Darensbourg, Carlos Baiz, Daniel P. Tabor
Two-dimensional infrared spectroscopy offers unique capabilities for probing vibrational coupling in complex metal–ligand systems. In this paper, we combine two-dimensional infrared spectroscopy with vibrational perturbation theory to investigate vibrational coupling in a diiron trinitrosyl complex across three stable redox states. Although these systems are challenging for electronic structure methods, we demonstrate that key features of experimental 2D IR spectra can be accurately reproduced using reduced-dimensional anharmonic calculations with a small harmonic frequency scaling. Analysis reveals that N–O stretching modes maintain high locality across all redox states, with coupling patterns that directly reflect variations in Fe–N bond strength. Using curvilinear coordinate analysis, we demonstrate that these differences result from systematic changes in cubic anharmonic force constants rather than mode delocalization. Our results establish N–O stretches as sensitive probes of metal–ligand bonding strength, expanding the toolkit for studying biologically relevant nitrosyl complexes.
{"title":"Low-Cost Calculation and Analysis of 2D IR Spectra of Model Diiron Trinitrosyl Complexes in the NO Stretch Region with Vibrational Perturbation Theory","authors":"Hayden A Moran, Abigail F. Moody, Mark A Boyer, Paul Garrett, Manuel Quiroz, Sarnali Sanfui, Marcetta Y. Darensbourg, Carlos Baiz, Daniel P. Tabor","doi":"10.1039/d5cp03578c","DOIUrl":"https://doi.org/10.1039/d5cp03578c","url":null,"abstract":"Two-dimensional infrared spectroscopy offers unique capabilities for probing vibrational coupling in complex metal–ligand systems. In this paper, we combine two-dimensional infrared spectroscopy with vibrational perturbation theory to investigate vibrational coupling in a diiron trinitrosyl complex across three stable redox states. Although these systems are challenging for electronic structure methods, we demonstrate that key features of experimental 2D IR spectra can be accurately reproduced using reduced-dimensional anharmonic calculations with a small harmonic frequency scaling. Analysis reveals that N–O stretching modes maintain high locality across all redox states, with coupling patterns that directly reflect variations in Fe–N bond strength. Using curvilinear coordinate analysis, we demonstrate that these differences result from systematic changes in cubic anharmonic force constants rather than mode delocalization. Our results establish N–O stretches as sensitive probes of metal–ligand bonding strength, expanding the toolkit for studying biologically relevant nitrosyl complexes.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"7 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048837","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}
Yuxue Zhao, Linlin Wu, Liangkai Xu, Rui Zou, Chang-Jun Liu
Supported gold catalysts are fundamentally and practically important for hydrogenation reactions due to their unique electronic properties and catalytic activity. In this work, Au nanoparticles were successfully deposited onto an In2O3 support via a deposition-precipitation method to form a Au/In2O3 catalyst, which was subsequently evaluated for CO2 hydrogenation under atmospheric pressure. This catalyst exhibits outstanding low-temperature activity for the reverse water gas shift (RWGS) reaction, achieving a CO2 conversion of 21.3%, a CO selectivity of 100%, and a CO formation rate of 0.30 mmolCO gcat-1 min-1 at 350 °C. Characterization results reveal that Au nanoparticles are uniformly dispersed on the In2O3 surface, accompanied by charge transfer from Au to the In2O3 support. This strong electronic metal-support interaction (EMSI) results in the formation of positively charged Auδ+ species, which facilitates H2 dissociation. Meanwhile, the generation of surface oxygen vacancies on In2O3 is promoted, enhancing CO2 adsorption and activation. These synergistic effects between Au nanoparticles and In2O3 account for the superior RWGS activities of the Au/In2O3 catalyst.
{"title":"A highly active Au/In<sub>2</sub>O<sub>3</sub> catalyst for the reverse water gas shift reaction.","authors":"Yuxue Zhao, Linlin Wu, Liangkai Xu, Rui Zou, Chang-Jun Liu","doi":"10.1039/d5cp04442a","DOIUrl":"https://doi.org/10.1039/d5cp04442a","url":null,"abstract":"<p><p>Supported gold catalysts are fundamentally and practically important for hydrogenation reactions due to their unique electronic properties and catalytic activity. In this work, Au nanoparticles were successfully deposited onto an In<sub>2</sub>O<sub>3</sub> support <i>via</i> a deposition-precipitation method to form a Au/In<sub>2</sub>O<sub>3</sub> catalyst, which was subsequently evaluated for CO<sub>2</sub> hydrogenation under atmospheric pressure. This catalyst exhibits outstanding low-temperature activity for the reverse water gas shift (RWGS) reaction, achieving a CO<sub>2</sub> conversion of 21.3%, a CO selectivity of 100%, and a CO formation rate of 0.30 mmol<sub>CO</sub> g<sub>cat</sub><sup>-1</sup> min<sup>-1</sup> at 350 °C. Characterization results reveal that Au nanoparticles are uniformly dispersed on the In<sub>2</sub>O<sub>3</sub> surface, accompanied by charge transfer from Au to the In<sub>2</sub>O<sub>3</sub> support. This strong electronic metal-support interaction (EMSI) results in the formation of positively charged Au<sup><i>δ</i>+</sup> species, which facilitates H<sub>2</sub> dissociation. Meanwhile, the generation of surface oxygen vacancies on In<sub>2</sub>O<sub>3</sub> is promoted, enhancing CO<sub>2</sub> adsorption and activation. These synergistic effects between Au nanoparticles and In<sub>2</sub>O<sub>3</sub> account for the superior RWGS activities of the Au/In<sub>2</sub>O<sub>3</sub> catalyst.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049623","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}
Flame plasmas can serve as unique electrochemical environments, enabling high-temperature electrochemistry in a gaseous medium. In this study, we explore electrochemistry in flame plasmas, focusing on the formation and characterisation of passive oxide layers on metals and alloys, notably platinum and titanium using electrochemical impedance spectroscopy (EIS). Also, we summarise the existing literature on flame plasma electrochemistry and discuss how EIS can probe the evolution of protective oxide films in these extreme conditions. The passivation behaviour of platinum and titanium is compared: platinum tends to form only a thin surface oxide, whereas titanium readily develops a thick TiO2 scale. The impedance response of these passive layers in a flame reveals distinct characteristics – from high impedance for platinum sparse oxide to low impedance features for TiO2 films that decrease with thickness. We examine the mass transport conditions in flame plasmas, where low ionic concentrations, high ionic mobility, strong convection, and significant migration effects differentiate flame electrochemistry from conventional liquid electrolytes and key equations are provided to describe the electrochemical processes, and all observations are contextualised with current theory and experimental findings.
{"title":"Electrochemistry in flame plasmas: passive films and impedance analysis","authors":"Bill Logan Riehl, Craig E. Banks","doi":"10.1039/d5cp03232f","DOIUrl":"https://doi.org/10.1039/d5cp03232f","url":null,"abstract":"Flame plasmas can serve as unique electrochemical environments, enabling high-temperature electrochemistry in a gaseous medium. In this study, we explore electrochemistry in flame plasmas, focusing on the formation and characterisation of passive oxide layers on metals and alloys, notably platinum and titanium using electrochemical impedance spectroscopy (EIS). Also, we summarise the existing literature on flame plasma electrochemistry and discuss how EIS can probe the evolution of protective oxide films in these extreme conditions. The passivation behaviour of platinum and titanium is compared: platinum tends to form only a thin surface oxide, whereas titanium readily develops a thick TiO<small><sub>2</sub></small> scale. The impedance response of these passive layers in a flame reveals distinct characteristics – from high impedance for platinum sparse oxide to low impedance features for TiO<small><sub>2</sub></small> films that decrease with thickness. We examine the mass transport conditions in flame plasmas, where low ionic concentrations, high ionic mobility, strong convection, and significant migration effects differentiate flame electrochemistry from conventional liquid electrolytes and key equations are provided to describe the electrochemical processes, and all observations are contextualised with current theory and experimental findings.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"4 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048835","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}
Harrison C. Oven, Himal Kanti Ganguly, Neal J. Zondlo
cis-Proline amide bonds are associated with substantial changes in protein structure, dynamics, and function. Approximately 5% of all proline amide bonds are in the cis conformation, but there is an incomplete understanding of local structural effects that stabilize cis-proline. We previously identified that cis-proline in Ser-Pro sequences is stabilized by a C–H/O interaction between the side-chain Ser oxygen and the proline C–H. Herein, via bioinformatics analysis, we found that C–H/O interactions between a side-chain oxygen and Pro C–H can stabilize the cis-proline conformation at Glu-Pro, Asp-Pro, Gln-Pro, Asn-Pro, Ser-Pro, and Thr-Pro sequences. These C–H/O interactions are apparently most stabilizing at Glu-Pro sequences, which have a substantially higher than average frequency of cis-proline (7.1% of all Glu-Pro amide bonds in the PDB). DFT calculations were conducted to understand the basis and geometries of C–H/O interactions in these sequences. Computationally, these residues all exhibit close C–H/O interactions (substantially below the 2.72 Å sum of the van der Waals radii of H and O), with the closest C–H/O interactions observed with the anionic oxygens of Glu and Asp, and with closer interactions for the anionic residues than the neutral carboxamides Gln and Asn. DFT calculations revealed that C–H/O interactions also stabilize cis-proline at phosphoserine-proline and phosphothreonine-proline sequences, with closer C–H/O interactions in the dianionic forms of phosphorylated residues that predominate at physiological pH. These results also provide an explanation for the observed higher activation barrier for amide bond isomerism at phosphoserine-proline and phosphothreonine-proline sequences. Calculations suggested that C–H/O interactions mediated by these residues could also stabilize non-proline cis amide bonds, which are often functionally important when observed.
{"title":"Proline/Sidechain C–H/O Interactions Stabilize cis-Proline","authors":"Harrison C. Oven, Himal Kanti Ganguly, Neal J. Zondlo","doi":"10.1039/d5cp03423j","DOIUrl":"https://doi.org/10.1039/d5cp03423j","url":null,"abstract":"cis-Proline amide bonds are associated with substantial changes in protein structure, dynamics, and function. Approximately 5% of all proline amide bonds are in the cis conformation, but there is an incomplete understanding of local structural effects that stabilize cis-proline. We previously identified that cis-proline in Ser-Pro sequences is stabilized by a C–H/O interaction between the side-chain Ser oxygen and the proline C–H. Herein, via bioinformatics analysis, we found that C–H/O interactions between a side-chain oxygen and Pro C–H can stabilize the cis-proline conformation at Glu-Pro, Asp-Pro, Gln-Pro, Asn-Pro, Ser-Pro, and Thr-Pro sequences. These C–H/O interactions are apparently most stabilizing at Glu-Pro sequences, which have a substantially higher than average frequency of cis-proline (7.1% of all Glu-Pro amide bonds in the PDB). DFT calculations were conducted to understand the basis and geometries of C–H/O interactions in these sequences. Computationally, these residues all exhibit close C–H/O interactions (substantially below the 2.72 Å sum of the van der Waals radii of H and O), with the closest C–H/O interactions observed with the anionic oxygens of Glu and Asp, and with closer interactions for the anionic residues than the neutral carboxamides Gln and Asn. DFT calculations revealed that C–H/O interactions also stabilize cis-proline at phosphoserine-proline and phosphothreonine-proline sequences, with closer C–H/O interactions in the dianionic forms of phosphorylated residues that predominate at physiological pH. These results also provide an explanation for the observed higher activation barrier for amide bond isomerism at phosphoserine-proline and phosphothreonine-proline sequences. Calculations suggested that C–H/O interactions mediated by these residues could also stabilize non-proline cis amide bonds, which are often functionally important when observed.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"40 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048836","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}
Oskar Asvany, Urs Graf, Weslley Guilherme Dias de Paiva Silva, Lea Schneider, Slawa Kabanovic, Volker Ossenkopf, Jürgen Stutzki, Igor Savić, Rolf Güsten, Oliver Ricken, Bernd Klein, Stephan Schlemmer
The J = 1 ← 0 fundamental rotational transition of HHe + at 2.010 THz has been revisited using a combination of a 4 K 22-pole ion trap apparatus and a high-power frequency multiplied THz source. For the detection of the resonant absorption, three different action spectroscopic techniques have been applied, one of which is demonstrated here for the first time (ejection of the ion upon pure rotational excitation). The different methods are evaluated and compared, and improve the accuracy and precision of the former transition value by one order of magnitude to 2010.183312(8) GHz.
{"title":"Revisiting the J = 1 ← 0 fundamental rotational transition of HHe + with action spectroscopy","authors":"Oskar Asvany, Urs Graf, Weslley Guilherme Dias de Paiva Silva, Lea Schneider, Slawa Kabanovic, Volker Ossenkopf, Jürgen Stutzki, Igor Savić, Rolf Güsten, Oliver Ricken, Bernd Klein, Stephan Schlemmer","doi":"10.1039/d5cp04689k","DOIUrl":"https://doi.org/10.1039/d5cp04689k","url":null,"abstract":"The J = 1 ← 0 fundamental rotational transition of HHe + at 2.010 THz has been revisited using a combination of a 4 K 22-pole ion trap apparatus and a high-power frequency multiplied THz source. For the detection of the resonant absorption, three different action spectroscopic techniques have been applied, one of which is demonstrated here for the first time (ejection of the ion upon pure rotational excitation). The different methods are evaluated and compared, and improve the accuracy and precision of the former transition value by one order of magnitude to 2010.183312(8) GHz.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"67 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048839","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}
Pau Capera-Aragones, Kavita Matange, Vahab Rajaei, Yuval Pinter, Anton S. Petrov, Loren Dean Williams, Moran Frenkel Pinter
The emergence of chemical selectivity poses a central challenge in origins-of-life research. As demonstrated by analyses of asteroid and meteorite samples, abiotic chemistry is incredibly messy. Experiments show that even limited sets of reactive species can undergo vast numbers of distinct chemical transformations, leading to a combinatorial explosion of products. These explosions arise from the numerous ways in which reactants in mixtures can combine, generating large and chemically diverse ensembles that reduce or even preclude the possibility of productive pathways of chemical evolution. However, recent empirical studies have demonstrated that under kinetic control, chemical systems can exhibit combinatorial compression—a marked reduction in product diversity relative to combinatorial expectations. This selective phenomenon is observed under conditions of low water activity, such as in the dry phase of wet–dry cycling experiments. Here, we integrate transition-state theory with computer simulations to demonstrate that experimentally observed combinatorial compression is a consequence of kinetic selection in condensation-dehydration reactions. Kinetic selection depends on several key factors: (i) chemical connectivity, where multiple species can react with each other; (ii) at least one particularly reactive species—termed a “kinetic compressor”; and (iii) appropriate temperature, concentrations, and reaction times. We find that small differences in activation free energies, on the order of just ~3 kcal/mol, can dominate a kinetic landscape, dramatically limiting product distributions. Connected systems can favor a narrow subset of products, suggesting selection mechanisms in prebiotic contexts. Our results provide mechanistic insight into combinatorial compression, establish a quantitative framework for exploring the emergence of stringent chemical selectivity, and can guide future experimental efforts in chemical evolution.
{"title":"Stringent Selection on Kinetics of Condensation Reactions: Early Steps in Chemical Evolution","authors":"Pau Capera-Aragones, Kavita Matange, Vahab Rajaei, Yuval Pinter, Anton S. Petrov, Loren Dean Williams, Moran Frenkel Pinter","doi":"10.1039/d5cp03057a","DOIUrl":"https://doi.org/10.1039/d5cp03057a","url":null,"abstract":"The emergence of chemical selectivity poses a central challenge in origins-of-life research. As demonstrated by analyses of asteroid and meteorite samples, abiotic chemistry is incredibly messy. Experiments show that even limited sets of reactive species can undergo vast numbers of distinct chemical transformations, leading to a combinatorial explosion of products. These explosions arise from the numerous ways in which reactants in mixtures can combine, generating large and chemically diverse ensembles that reduce or even preclude the possibility of productive pathways of chemical evolution. However, recent empirical studies have demonstrated that under kinetic control, chemical systems can exhibit combinatorial compression—a marked reduction in product diversity relative to combinatorial expectations. This selective phenomenon is observed under conditions of low water activity, such as in the dry phase of wet–dry cycling experiments. Here, we integrate transition-state theory with computer simulations to demonstrate that experimentally observed combinatorial compression is a consequence of kinetic selection in condensation-dehydration reactions. Kinetic selection depends on several key factors: (i) chemical connectivity, where multiple species can react with each other; (ii) at least one particularly reactive species—termed a “kinetic compressor”; and (iii) appropriate temperature, concentrations, and reaction times. We find that small differences in activation free energies, on the order of just ~3 kcal/mol, can dominate a kinetic landscape, dramatically limiting product distributions. Connected systems can favor a narrow subset of products, suggesting selection mechanisms in prebiotic contexts. Our results provide mechanistic insight into combinatorial compression, establish a quantitative framework for exploring the emergence of stringent chemical selectivity, and can guide future experimental efforts in chemical evolution.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"292 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048830","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}
Zhuxiao Li, Zhiru Zhang, Jianxiang Xin, Yuxiang Bu, Xinyu Song
The direct evidence of carbon-carbon one-electron σ-bonds marks a significant breakthrough in carbon-based materials; however, the spin coupling properties between such bonds and other spin sources in coexisting structures remain unexplored. In this work, we propose a molecular engineering strategy to modify the hexaphenylethane derivatives that contain both a carbon-carbon one-electron σ-bond (σ C•C ) and an additional spin source (a radical group). By introducing substituents with conjugative effects, we induce cross-plane spin polarization, thereby modulating the spin-spin coupling between the two spin sources. These substituents regulate the distribution of the unpaired electrons within the π-system via a pushpull effect, enabling fine-tuning of the magnetic coupling interaction between the σ C•C and an additional radical group. Results indicate that the unsubstituted structure exhibits weak ferromagnetic (FM) coupling (J = 75.46 cm⁻¹). Notably, the introduction of substituents not only significantly alters the magnitude of magnetic coupling but also modifies the magnetic nature, with the magnetic coupling constant J spanning a wide range from -720.74 cm -1 to 416.28 cm -1 . Molecular orbital analyses reveal that substituents influence the singly occupied molecular orbitals (SOMOs) through extended conjugation, modifying both the energy gap and spatial overlap of the two SOMOs, and thus tailoring the magnetic behavior. These findings demonstrate a novel strategy for indirect magnetic regulation in the carbon-based spintronic devices.
碳-碳单电子σ键的直接证据标志着碳基材料的重大突破；然而，这些键与共存结构中其他自旋源之间的自旋耦合特性仍未被探索。在这项工作中，我们提出了一种分子工程策略来修饰含有碳碳单电子σ键（σ C•C）和附加自旋源（自由基）的六苯乙烷衍生物。通过引入具有共轭效应的取代基，我们诱导了交叉平面自旋极化，从而调制了两个自旋源之间的自旋耦合。这些取代基通过推拉效应调节π系内未配对电子的分布，使σ C•C与附加基团之间的磁耦合相互作用得以微调。结果表明，未取代结构呈现弱铁磁耦合（J = 75.46 cm⁻¹）。值得注意的是，取代基的引入不仅显著改变了磁耦合的大小，而且改变了磁性性质，磁耦合常数J在-720.74 cm -1到416.28 cm -1的范围内变化。分子轨道分析表明，取代基通过扩展共轭影响单占据分子轨道（SOMOs），改变两个SOMOs的能隙和空间重叠，从而调整磁性行为。这些发现为碳基自旋电子器件的间接磁调节提供了一种新的策略。
{"title":"Cross-Plane Magnetic Coupling in Carbon-Based Diradicals with One-Electron σ-Bond Regulated by Conjugative Substituent Engineering","authors":"Zhuxiao Li, Zhiru Zhang, Jianxiang Xin, Yuxiang Bu, Xinyu Song","doi":"10.1039/d5cp04210k","DOIUrl":"https://doi.org/10.1039/d5cp04210k","url":null,"abstract":"The direct evidence of carbon-carbon one-electron σ-bonds marks a significant breakthrough in carbon-based materials; however, the spin coupling properties between such bonds and other spin sources in coexisting structures remain unexplored. In this work, we propose a molecular engineering strategy to modify the hexaphenylethane derivatives that contain both a carbon-carbon one-electron σ-bond (σ C•C ) and an additional spin source (a radical group). By introducing substituents with conjugative effects, we induce cross-plane spin polarization, thereby modulating the spin-spin coupling between the two spin sources. These substituents regulate the distribution of the unpaired electrons within the π-system via a pushpull effect, enabling fine-tuning of the magnetic coupling interaction between the σ C•C and an additional radical group. Results indicate that the unsubstituted structure exhibits weak ferromagnetic (FM) coupling (J = 75.46 cm⁻¹). Notably, the introduction of substituents not only significantly alters the magnitude of magnetic coupling but also modifies the magnetic nature, with the magnetic coupling constant J spanning a wide range from -720.74 cm -1 to 416.28 cm -1 . Molecular orbital analyses reveal that substituents influence the singly occupied molecular orbitals (SOMOs) through extended conjugation, modifying both the energy gap and spatial overlap of the two SOMOs, and thus tailoring the magnetic behavior. These findings demonstrate a novel strategy for indirect magnetic regulation in the carbon-based spintronic devices.","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146048841","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}
Tomás González-Lezana, Maarten Konings, Jérôme Loreau, François Lique, Milan Sil, Alexandre Faure
A systematic investigation on the different processes involving formation, destruction and (de)excitation of specific rovibrational states of CH+ has been carried out based on statistical approaches. Thus, reactive collisions between C+(2P) and H2(v, j) and between CH+(v, j) and H for a large number of state-to-state transitions have been studied using a statistical quantum method and a statistical adiabatic channel model. The capabilities of such techniques for the study of the title system are discussed with comparisons to previous quantum mechanical results and experimental data. Integral cross sections as a function of the energy and rate constants in terms of the temperature (up to 1500 K) are obtained and numerical data for astrophysical purposes are provided.
{"title":"Rate constants for a reactive system of astrophysical interest: a statistical study of CH<sub>2</sub><sup />.","authors":"Tomás González-Lezana, Maarten Konings, Jérôme Loreau, François Lique, Milan Sil, Alexandre Faure","doi":"10.1039/d5cp04254b","DOIUrl":"10.1039/d5cp04254b","url":null,"abstract":"<p><p>A systematic investigation on the different processes involving formation, destruction and (de)excitation of specific rovibrational states of CH<sup>+</sup> has been carried out based on statistical approaches. Thus, reactive collisions between C<sup>+</sup>(<sup>2</sup>P) and H<sub>2</sub>(<i>v</i>, <i>j</i>) and between CH<sup>+</sup>(<i>v</i>, <i>j</i>) and H for a large number of state-to-state transitions have been studied using a statistical quantum method and a statistical adiabatic channel model. The capabilities of such techniques for the study of the title system are discussed with comparisons to previous quantum mechanical results and experimental data. Integral cross sections as a function of the energy and rate constants in terms of the temperature (up to 1500 K) are obtained and numerical data for astrophysical purposes are provided.</p>","PeriodicalId":99,"journal":{"name":"Physical Chemistry Chemical Physics","volume":" ","pages":""},"PeriodicalIF":2.9,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12839827/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146049591","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}
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