Pub Date : 2020-08-11DOI: 10.1080/0144235x.2020.1794097
Minzhong Xu, P. Felker, Z. Bačić
The translation-rotation (TR) dynamics and spectroscopy of light molecules, e.g. H , HD, HF, and H O, inside nanoscale cavities such as those of fullerenes and in clathrate hydrates, is dominated by strong nuclear quantum effects (NQEs) to a degree that is without parallel among realistic molecular species. The NQEs include the large TR zero-point energy, quantisation of the translational centre-of-mass motions of the guest molecule, the coupling of various angular momenta in the system, and nuclear spin isomerism. They leave rich and intriguing fingerprints in the inelastic neutron scattering (INS) spectra arising from the transitions between the TR levels of the systems studied. Here we describe the major methodological advances made in the past decade, in both bound-state and scattering calculations that, when combined, have led to the novel and powerful approach for rigorous quantum simulations of the INS spectra a diatomic molecule, homo- and heteronuclear, inside a nanocavity of an arbitrary geometry. As illustrated by several demanding applications, these simulations have been indispensable, and very successful, for the assignment and interpretation of the measured INS spectra. Very surprisingly, this effort has also resulted in the completely unexpected, precedent-setting discovery of the INS selection rule for diatomic molecules in near-spherical nanocavities, overturning the widely accepted view that the INS has no selection rules.
{"title":"Light molecules inside the nanocavities of fullerenes and clathrate hydrates: inelastic neutron scattering spectra and the unexpected selection rule from rigorous quantum simulations","authors":"Minzhong Xu, P. Felker, Z. Bačić","doi":"10.1080/0144235x.2020.1794097","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1794097","url":null,"abstract":"The translation-rotation (TR) dynamics and spectroscopy of light molecules, e.g. H , HD, HF, and H O, inside nanoscale cavities such as those of fullerenes and in clathrate hydrates, is dominated by strong nuclear quantum effects (NQEs) to a degree that is without parallel among realistic molecular species. The NQEs include the large TR zero-point energy, quantisation of the translational centre-of-mass motions of the guest molecule, the coupling of various angular momenta in the system, and nuclear spin isomerism. They leave rich and intriguing fingerprints in the inelastic neutron scattering (INS) spectra arising from the transitions between the TR levels of the systems studied. Here we describe the major methodological advances made in the past decade, in both bound-state and scattering calculations that, when combined, have led to the novel and powerful approach for rigorous quantum simulations of the INS spectra a diatomic molecule, homo- and heteronuclear, inside a nanocavity of an arbitrary geometry. As illustrated by several demanding applications, these simulations have been indispensable, and very successful, for the assignment and interpretation of the measured INS spectra. Very surprisingly, this effort has also resulted in the completely unexpected, precedent-setting discovery of the INS selection rule for diatomic molecules in near-spherical nanocavities, overturning the widely accepted view that the INS has no selection rules.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89051981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-02DOI: 10.1080/0144235x.2020.1777705
S. Stephan, H. Hasse
Component density profiles at vapour–liquid interfaces of mixtures can exhibit a non-monotonic behaviour with a maximum that can be many times larger than the densities in the bulk phases. This is called enrichment and is usually only observed for low-boiling components. The enrichment is a nanoscopic property which can presently not be measured experimentally – in contrast to the classical Gibbs adsorption. The available information on the enrichment stems from molecular simulations, density gradient theory, or density functional theory. The enrichment is highly interesting as it is suspected to influence the mass transfer across interfaces. In the present work, we review the literature data and the existing knowledge on this phenomenon and propose an empirical model to establish a link between the nanoscopic enrichment and macroscopic properties – namely vapour–liquid equilibrium data. The model parameters were determined from a fit to a dataset on the enrichment in about 100 binary Lennard-Jones model mixtures that exhibit different types of phase behaviour, which has recently become available. The model is then tested on the entire set of enrichment data that is available in the literature, which includes also mixtures containing non-spherical, polar, and H-bonding components. The model predicts the enrichment data from the literature (2,000 data points) with an AAD of about 16%, which is below the uncertainty of the enrichment data. This establishes a direct link between measurable macroscopic properties and the nanoscopic enrichment and enables predictions of the enrichment at vapour–liquid interfaces from macroscopic data alone.
{"title":"Enrichment at vapour–liquid interfaces of mixtures: establishing a link between nanoscopic and macroscopic properties","authors":"S. Stephan, H. Hasse","doi":"10.1080/0144235x.2020.1777705","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1777705","url":null,"abstract":"Component density profiles at vapour–liquid interfaces of mixtures can exhibit a non-monotonic behaviour with a maximum that can be many times larger than the densities in the bulk phases. This is called enrichment and is usually only observed for low-boiling components. The enrichment is a nanoscopic property which can presently not be measured experimentally – in contrast to the classical Gibbs adsorption. The available information on the enrichment stems from molecular simulations, density gradient theory, or density functional theory. The enrichment is highly interesting as it is suspected to influence the mass transfer across interfaces. In the present work, we review the literature data and the existing knowledge on this phenomenon and propose an empirical model to establish a link between the nanoscopic enrichment and macroscopic properties – namely vapour–liquid equilibrium data. The model parameters were determined from a fit to a dataset on the enrichment in about 100 binary Lennard-Jones model mixtures that exhibit different types of phase behaviour, which has recently become available. The model is then tested on the entire set of enrichment data that is available in the literature, which includes also mixtures containing non-spherical, polar, and H-bonding components. The model predicts the enrichment data from the literature (2,000 data points) with an AAD of about 16%, which is below the uncertainty of the enrichment data. This establishes a direct link between measurable macroscopic properties and the nanoscopic enrichment and enables predictions of the enrichment at vapour–liquid interfaces from macroscopic data alone.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85484897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-02DOI: 10.1080/0144235x.2020.1782651
C. Cabezas, M. Nakajima, Y. Endo
Carbonyl oxides, R1R2COO, alternatively known as Criegee intermediates (CIs), are short-lived molecules produced from ozonolysis of alkenes. These ozonolysis reactions yield highly excited CIs, and most of them promptly decay with emission of the OH radical and other products. Some of the nascent CIs are stabilised by collisional relaxation with surrounding molecules, and react with atmospheric trace constituents, such as SO2 and gaseous organic compounds, converting them to more highly oxygenated molecules relevant to formation of aerosols. Hence, reactions of CIs are of central interest for atmospheric chemists. Physico-chemical properties of CIs are strongly related to their geometrical and electronic structures, which are often discussed based on spectroscopic information. Especially, very high resolution rotational spectroscopy provides critical information about molecular structures and intramolecular dynamics, and also enables us to probe individual isomers, conformers, and isotopologues, with complete selectivity. This article reviews the rotational investigations carried out on several CIs, their bimolecular complexes and primary reaction products, focusing on their molecular structure, conformational behaviour and reactivity.
{"title":"Criegee intermediates meet rotational spectroscopy","authors":"C. Cabezas, M. Nakajima, Y. Endo","doi":"10.1080/0144235x.2020.1782651","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1782651","url":null,"abstract":"Carbonyl oxides, R1R2COO, alternatively known as Criegee intermediates (CIs), are short-lived molecules produced from ozonolysis of alkenes. These ozonolysis reactions yield highly excited CIs, and most of them promptly decay with emission of the OH radical and other products. Some of the nascent CIs are stabilised by collisional relaxation with surrounding molecules, and react with atmospheric trace constituents, such as SO2 and gaseous organic compounds, converting them to more highly oxygenated molecules relevant to formation of aerosols. Hence, reactions of CIs are of central interest for atmospheric chemists. Physico-chemical properties of CIs are strongly related to their geometrical and electronic structures, which are often discussed based on spectroscopic information. Especially, very high resolution rotational spectroscopy provides critical information about molecular structures and intramolecular dynamics, and also enables us to probe individual isomers, conformers, and isotopologues, with complete selectivity. This article reviews the rotational investigations carried out on several CIs, their bimolecular complexes and primary reaction products, focusing on their molecular structure, conformational behaviour and reactivity.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81095285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-02DOI: 10.1080/0144235x.2020.1765598
S. Roy, Nayanthara K. J., N. Tiwari, A. Tiwari
Dissociative chemisorption is one of the most significant steps in heterogeneous catalysis. The rate-limiting step for industrially important processes such as water gas-shift reaction and steam reforming of methane involves the dissociative chemisorption of water and methane, respectively. These reactions exhibit interesting mode-specificity and show a strong dependence on the surface temperature of the catalyst. The metals commonly used in industry as catalysts for these two processes have their own limitations. Certain bimetallic surfaces and subsurface alloys are suggested, which could be regarded as potential catalysts for these two industrial processes. How transition states are modified by the motion of the lattice atom during the reactions are shown using electronic structure calculations. In the present review, we have focused on the lattice atom distortion in the transition state, semi-classical tunnelling probability, and the influence of surface temperature on reactivity. Quantum dynamics study for H O dissociation on metal surface is explored using three-dimensional London-Eyring-Polanyi-Sato potential energy surface. A full quantum mechanical approach following reaction path Hamiltonian is also studied by including the effects of lattice motion and site averaging. The effects of initial vibrational mode on reactivity are reported. Vibrational efficacy is examined in terms of vibrational non-adiabatic couplings.
{"title":"Energetics and dynamics of CH4 and H2O dissociation on metal surfaces","authors":"S. Roy, Nayanthara K. J., N. Tiwari, A. Tiwari","doi":"10.1080/0144235x.2020.1765598","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1765598","url":null,"abstract":"Dissociative chemisorption is one of the most significant steps in heterogeneous catalysis. The rate-limiting step for industrially important processes such as water gas-shift reaction and steam reforming of methane involves the dissociative chemisorption of water and methane, respectively. These reactions exhibit interesting mode-specificity and show a strong dependence on the surface temperature of the catalyst. The metals commonly used in industry as catalysts for these two processes have their own limitations. Certain bimetallic surfaces and subsurface alloys are suggested, which could be regarded as potential catalysts for these two industrial processes. How transition states are modified by the motion of the lattice atom during the reactions are shown using electronic structure calculations. In the present review, we have focused on the lattice atom distortion in the transition state, semi-classical tunnelling probability, and the influence of surface temperature on reactivity. Quantum dynamics study for H O dissociation on metal surface is explored using three-dimensional London-Eyring-Polanyi-Sato potential energy surface. A full quantum mechanical approach following reaction path Hamiltonian is also studied by including the effects of lattice motion and site averaging. The effects of initial vibrational mode on reactivity are reported. Vibrational efficacy is examined in terms of vibrational non-adiabatic couplings.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87935039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-07-02DOI: 10.1080/0144235x.2020.1792104
R. Chhantyal-Pun, M. Khan, C. Taatjes, C. Percival, A. Orr-Ewing, D. Shallcross
In the context of tropospheric chemistry, Criegee intermediates denote carbonyl oxides with biradical/zwitterionic character (R1R2COO) that form during the ozonolysis of alkenes. First discovered almost 70 years ago, stabilised versions of Criegee intermediates formed via collisional removal of excess energy have interesting kinetic and mechanistic properties. The direct production and detection of these intermediates were not reported in the literature until 2008. However, recent advances in their generation through the ultraviolet irradiation of the corresponding diiodoalkanes in excess O2 and detection by various spectroscopic techniques (photoionisation, ultraviolet, infrared, microwave and mass spectrometry) have shown that these species can react rapidly with closed-shell molecules, in many cases at or exceeding the classical gas-kinetic limit, via multiple reaction pathways. These reactions can be complex, and laboratory measurements of products and the temperature and pressure dependence of the reaction kinetics have also revealed unusual behaviour. The potential role of these intermediates in atmospheric chemistry is significant, altering models of the oxidising capacity of the Earth's atmosphere and the rate of generation of secondary organic aerosol.
{"title":"Criegee intermediates: production, detection and reactivity","authors":"R. Chhantyal-Pun, M. Khan, C. Taatjes, C. Percival, A. Orr-Ewing, D. Shallcross","doi":"10.1080/0144235x.2020.1792104","DOIUrl":"https://doi.org/10.1080/0144235x.2020.1792104","url":null,"abstract":"In the context of tropospheric chemistry, Criegee intermediates denote carbonyl oxides with biradical/zwitterionic character (R1R2COO) that form during the ozonolysis of alkenes. First discovered almost 70 years ago, stabilised versions of Criegee intermediates formed via collisional removal of excess energy have interesting kinetic and mechanistic properties. The direct production and detection of these intermediates were not reported in the literature until 2008. However, recent advances in their generation through the ultraviolet irradiation of the corresponding diiodoalkanes in excess O2 and detection by various spectroscopic techniques (photoionisation, ultraviolet, infrared, microwave and mass spectrometry) have shown that these species can react rapidly with closed-shell molecules, in many cases at or exceeding the classical gas-kinetic limit, via multiple reaction pathways. These reactions can be complex, and laboratory measurements of products and the temperature and pressure dependence of the reaction kinetics have also revealed unusual behaviour. The potential role of these intermediates in atmospheric chemistry is significant, altering models of the oxidising capacity of the Earth's atmosphere and the rate of generation of secondary organic aerosol.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83426849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-02DOI: 10.1080/0144235X.2020.1757942
Joseph S. Beckwith, C. Rumble, E. Vauthey
ABSTRACT Time-resolved electronic spectroscopy has grown into a technique that provides hundreds to thousands of electronic spectra with femtosecond time resolution. This enables complex questions to be interrogated, with an obvious cost that the data are more detailed and thus require accurate modelling to be properly reproduced. Analysis of these data comes in a variety of forms, starting with a variety of assumptions about how the data may be decomposed. Here, four different types of analysis commonly used are discussed: band-shape analysis, global kinetic analysis, lifetime distribution models, and soft-modelling. This review provides a ‘user's guide’ to these various methods of data analysis, and attempts to elucidate their successes, domains in which they may be useful, and potential pitfalls in their usage.
{"title":"Data analysis in transient electronic spectroscopy – an experimentalist's view","authors":"Joseph S. Beckwith, C. Rumble, E. Vauthey","doi":"10.1080/0144235X.2020.1757942","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1757942","url":null,"abstract":"ABSTRACT Time-resolved electronic spectroscopy has grown into a technique that provides hundreds to thousands of electronic spectra with femtosecond time resolution. This enables complex questions to be interrogated, with an obvious cost that the data are more detailed and thus require accurate modelling to be properly reproduced. Analysis of these data comes in a variety of forms, starting with a variety of assumptions about how the data may be decomposed. Here, four different types of analysis commonly used are discussed: band-shape analysis, global kinetic analysis, lifetime distribution models, and soft-modelling. This review provides a ‘user's guide’ to these various methods of data analysis, and attempts to elucidate their successes, domains in which they may be useful, and potential pitfalls in their usage.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85030453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-04-02DOI: 10.1080/0144235X.2020.1764778
B. Tsukerblat, A. Palii, J. Clemente-Juan, E. Coronado
The purpose of this article is to answer the question of how symmetry helps us to investigate and understand the properties of nanoscopic magnetic clusters with complex structures. The systems of choice will be the three types of polyoxometalates (POMs): (1) POMs containing localised spins; (2) reduced mixed-valence (MV) POMs; (3) partially delocalised POMs in which localised and delocalised subunits coexist and interact. The theoretical tools based on various kinds of symmetry are the following: (1) irreducible tensor operator (ITO) approach based on the so-called “spin-symmetry” and MAGPACK program; (2) group-theoretical assignment of the exchange multiplets based on spin- and point symmetries; (3) group-theoretical classification of the delocalised electronic and electron-vibrational states of MV POMs; (4) general approach (based on spin symmetry) to evaluate the energy levels of large MV clusters and the corresponding MVPACK program; (5) computational approach (employing point symmetry) to solve multidimensional non-adiabatic vibronic problems in the nanoscopic systems realized as VIBPACK software. We made it our goal to avoid a conventional deductive style of presentation. On the contrary, we first consider specially selected complex POMs and then show by what methods and in what way the theoretical problems arising in the description of the properties of these molecules can be properly solved.
{"title":"Modelling the properties of magnetic clusters with complex structures: how symmetry can help us","authors":"B. Tsukerblat, A. Palii, J. Clemente-Juan, E. Coronado","doi":"10.1080/0144235X.2020.1764778","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1764778","url":null,"abstract":"The purpose of this article is to answer the question of how symmetry helps us to investigate and understand the properties of nanoscopic magnetic clusters with complex structures. The systems of choice will be the three types of polyoxometalates (POMs): (1) POMs containing localised spins; (2) reduced mixed-valence (MV) POMs; (3) partially delocalised POMs in which localised and delocalised subunits coexist and interact. The theoretical tools based on various kinds of symmetry are the following: (1) irreducible tensor operator (ITO) approach based on the so-called “spin-symmetry” and MAGPACK program; (2) group-theoretical assignment of the exchange multiplets based on spin- and point symmetries; (3) group-theoretical classification of the delocalised electronic and electron-vibrational states of MV POMs; (4) general approach (based on spin symmetry) to evaluate the energy levels of large MV clusters and the corresponding MVPACK program; (5) computational approach (employing point symmetry) to solve multidimensional non-adiabatic vibronic problems in the nanoscopic systems realized as VIBPACK software. We made it our goal to avoid a conventional deductive style of presentation. On the contrary, we first consider specially selected complex POMs and then show by what methods and in what way the theoretical problems arising in the description of the properties of these molecules can be properly solved.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75045473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-03-25DOI: 10.1080/0144235X.2020.1736401
S. Gordon, A. Osterwalder
Energy transfer reactions occur in all areas of chemistry. One fundamental form of this is demonstrated by reactions in which an electronically excited atom transfers energy to a neutral, resulting in spontaneous ionisation, potentially combined with complex formation, or dissociation. Our laboratory explores these reactions and seeks to understand the fundamental aspects of the energy exchange and how the reaction proceeds from reagents to products. We particularly seek to manipulate and control the collision energy and the reagent polarisation and understand their role in constraining the reaction outcome. The steric control of the reagents opens up opportunities for the manipulation of reaction channel branching and thus the probability of forming particular products. By simultaneously maintaining control over the collision energy we are able to manipulate the course of ion forming reactions with unparalleled precision.
{"title":"The stereodynamics of ion forming reactions","authors":"S. Gordon, A. Osterwalder","doi":"10.1080/0144235X.2020.1736401","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1736401","url":null,"abstract":"Energy transfer reactions occur in all areas of chemistry. One fundamental form of this is demonstrated by reactions in which an electronically excited atom transfers energy to a neutral, resulting in spontaneous ionisation, potentially combined with complex formation, or dissociation. Our laboratory explores these reactions and seeks to understand the fundamental aspects of the energy exchange and how the reaction proceeds from reagents to products. We particularly seek to manipulate and control the collision energy and the reagent polarisation and understand their role in constraining the reaction outcome. The steric control of the reagents opens up opportunities for the manipulation of reaction channel branching and thus the probability of forming particular products. By simultaneously maintaining control over the collision energy we are able to manipulate the course of ion forming reactions with unparalleled precision.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87355469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/0144235X.2020.1688530
T. A. Stephenson, M. Lester
ABSTRACT Criegee intermediates are reactive species formed in the ozonolysis of alkenes. Their subsequent chemistry is critical to an accounting of OH production, aerosol formation, and the oxidative capacity of the atmosphere. The fate of Criegee intermediates in the atmosphere is determined by the competition between bimolecular and unimolecular processes, so an understanding of unimolecular decay is an important topic in both atmospheric and physical chemistry. The unimolecular decay dynamics of Criegee intermediates is sensitive to the nature and conformation of its substituents. Multiple isomerisation pathways are possible, with some structures capable of a 1,4-hydrogen transfer reaction that is efficient, and generally competes with bimolecular reactions. Experimental studies that provide energy-resolved rate constants (k(E)) offer benchmarks for RRKM calculations that can be extrapolated to thermal rate constants (k(T)) under atmospheric conditions. The comparison of k(E) and k(T) values among a series of homologous Criegee intermediates provides insights into the role of structure, energetics, and tunnelling in the unimolecular decay dynamics of these species. Alternative unimolecular decay pathways also illuminate aspects of the dynamics of Criegee intermediates. These pathways are less susceptible to tunnelling, may be slower or faster than hydrogen transfer processes, and thus more or less competitive with bimolecular reactions.
{"title":"Unimolecular decay dynamics of Criegee intermediates: Energy-resolved rates, thermal rates, and their atmospheric impact","authors":"T. A. Stephenson, M. Lester","doi":"10.1080/0144235X.2020.1688530","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1688530","url":null,"abstract":"ABSTRACT Criegee intermediates are reactive species formed in the ozonolysis of alkenes. Their subsequent chemistry is critical to an accounting of OH production, aerosol formation, and the oxidative capacity of the atmosphere. The fate of Criegee intermediates in the atmosphere is determined by the competition between bimolecular and unimolecular processes, so an understanding of unimolecular decay is an important topic in both atmospheric and physical chemistry. The unimolecular decay dynamics of Criegee intermediates is sensitive to the nature and conformation of its substituents. Multiple isomerisation pathways are possible, with some structures capable of a 1,4-hydrogen transfer reaction that is efficient, and generally competes with bimolecular reactions. Experimental studies that provide energy-resolved rate constants (k(E)) offer benchmarks for RRKM calculations that can be extrapolated to thermal rate constants (k(T)) under atmospheric conditions. The comparison of k(E) and k(T) values among a series of homologous Criegee intermediates provides insights into the role of structure, energetics, and tunnelling in the unimolecular decay dynamics of these species. Alternative unimolecular decay pathways also illuminate aspects of the dynamics of Criegee intermediates. These pathways are less susceptible to tunnelling, may be slower or faster than hydrogen transfer processes, and thus more or less competitive with bimolecular reactions.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81976114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/0144235X.2020.1719699
Qinqin Yuan, W. Cao, Xue‐Bin Wang
Negative ion photoelectron spectroscopy (NIPES) coupled with electrospray ionisation (ESI) has been proven to be a powerful gas-phase spectroscopic tool for characterising electronic structures, chemical bonding of a variety of cluster anions, and corresponding neutral radicals involved in the condensed phase reactions and transformations. Since the acquisition of cryogenic and temperature-controlling capabilities, a broader range of research has been covered. This review summarises our recent investigations on metal complexes employing cryogenic ESI-NIPES that provides essential information towards understanding complicated condensed phase reactions, including hydrocarbon activations and electron transfer reactions, and affords spectroscopic perspective of highly reactive transient species and intimate redox pairs. Special attention has been drawn to connect gas phase photodetachment processes with solution phase redox reactions. Photodetachment of transition metal-EDTA complexes has been systematically investigated to model the sequential oxidation reactions of these species in solutions. For each series of homologous metal complexes, the obtained gas phase electron affinity (EA) is compared with the solution redox potential (E1/2) and the metal ionisation potential (IP) to emphasise their intrinsic correlations, with deviations being largely modulated by different degrees of ligand participations.
{"title":"Cryogenic and temperature-dependent photoelectron spectroscopy of metal complexes","authors":"Qinqin Yuan, W. Cao, Xue‐Bin Wang","doi":"10.1080/0144235X.2020.1719699","DOIUrl":"https://doi.org/10.1080/0144235X.2020.1719699","url":null,"abstract":"Negative ion photoelectron spectroscopy (NIPES) coupled with electrospray ionisation (ESI) has been proven to be a powerful gas-phase spectroscopic tool for characterising electronic structures, chemical bonding of a variety of cluster anions, and corresponding neutral radicals involved in the condensed phase reactions and transformations. Since the acquisition of cryogenic and temperature-controlling capabilities, a broader range of research has been covered. This review summarises our recent investigations on metal complexes employing cryogenic ESI-NIPES that provides essential information towards understanding complicated condensed phase reactions, including hydrocarbon activations and electron transfer reactions, and affords spectroscopic perspective of highly reactive transient species and intimate redox pairs. Special attention has been drawn to connect gas phase photodetachment processes with solution phase redox reactions. Photodetachment of transition metal-EDTA complexes has been systematically investigated to model the sequential oxidation reactions of these species in solutions. For each series of homologous metal complexes, the obtained gas phase electron affinity (EA) is compared with the solution redox potential (E1/2) and the metal ionisation potential (IP) to emphasise their intrinsic correlations, with deviations being largely modulated by different degrees of ligand participations.","PeriodicalId":54932,"journal":{"name":"International Reviews in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":6.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86684687","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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