The Journal of Physical Chemistry A最新文献

{"title":"Experimental and Theoretical Investigation of 2-Methylbenzothiazole Oxidation by OH in Air and the Role of O₂ and NO.","authors":"Weihong Wang, Natalia V Karimova, R Benny Gerber, Barbara J Finlayson-Pitts","doi":"10.1021/acs.jpca.5c00826","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c00826","url":null,"abstract":"<p><p>Benzothiazoles are in widespread use as components of, or precursors to, a variety of consumer and industrial products. This class of compounds encompasses the simplest molecule benzothiazole (BTH) in which a benzene ring is fused to a thiazole ring, as well as a series of derivatives which are commonly functionalized at the C2 position of the thiazole ring. The addition of groups at this position modifies the reactivity in ways that are not well-known. While the reactions of benzothiazoles in water have been the subject of investigation, in part for wastewater treatment applications, much less is known about their atmospheric reactions where gas phase oxidation by the OH radical is expected to dominate. We report here studies of the kinetics, products, and mechanism of reaction of 2-methylbenzothiazole (MeBTH) with OH in the gas phase using a combination of experiments and theory. Comparison to previous studies of the OH oxidation of BTH highlights the impact of substitution of a methyl group at the 2-position on the products and reactivity. Specifically, the rate constant at 298 K and 1 atm pressure for the MeBTH-OH reaction is (3.0 ± 0.4) × 10^-12 cm³ molecule^-1 s^-1 (1σ), about 50% faster than that of BTH. In addition, attack of OH on the -CH₃ group at the 2-position of the thiazole ring to form the aldehyde as the stable product becomes important, accounting for ∼ 33% of the overall reaction. Formation of the phenol-type products from attack on the benzene ring accounts for the remainder, with the experimental relative yields consistent with theoretical predictions based on energies of formation of the prereaction MeBTH···OH complex. The formation of the aldehyde product (2-CHO-BTH) involves a sequence of five distinct stages involving two oxygen molecules and one NO. Both processes involve a spin flip of unpaired electrons, which enables a transition between electronic states that is essential for the reaction to proceed. Using the room temperature rate constant, the estimated lifetimes of MeBTH in air range from about 9 h to 4 days over OH concentrations of 10⁷ - 10⁶ cm^-3. Thus, this reaction represents a significant loss process for MeBTH in air both outdoors and indoors, and exposures and toxicity of both the parent MeBTH and its oxidation products need to be taken into account in assessments of its environmental fates.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143750290","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}

{"title":"Binding Motifs of Doubly and Singly Charged Proton-Bound Clusters of B₁₂F₁₂^2- and Diaminoalkanes.","authors":"Arthur E Lee, Patrick Thomas, Courtney Kates, Terrance B McMahon, W Scott Hopkins","doi":"10.1021/acs.jpca.4c08341","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c08341","url":null,"abstract":"<p><p>The complexation of perfluorinated dodecaborate, B₁₂F₁₂^2-, with protonated diaminoalkanes, [H₂N(CH₂)<i>_n</i>H₂N] (<i>n=</i> 2 - 12), is studied with a combination of infrared multiple photon dissociation (IRMPD) action spectroscopy and ion mobility spectrometry. Singly charged clusters of the form [B₁₂F₁₂ + H₂N(CH₂)<i>_n</i>H₂N + H]^- (<i>n =</i> 2-12) and doubly charged clusters of the form [2B₁₂F₁₂ + H₂N(CH₂)<i>_n</i>H₂N + 2H]^2- (<i>n =</i> 2-12) are observed and characterized experimentally and computationally. For the singly charged clusters, low-energy structural motifs associated with monodentate and bidentate binding motifs of the diaminoalkane are computed via a combination of CREST conformer exploration and density functional theory. For the doubly charged clusters, the doubly protonated diaminoalkane acts as a tether between two B₁₂F₁₂^2- cages. Major product channels of the singly charged and doubly charged species are found to be the formation of HB₁₂F₁₂^- via proton transfer and the loss of B₁₂F₁₂^2-. The fragmentation of HB₁₂F₁₂^- leads to several secondary products, including [B₁₂F₁₁ + N₂]^-. Collision cross sections (CCSs) for the singly charged clusters are reported, and the major subpopulation of the gas phase ensemble for the different singly charged species is the bidentate conformation.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143750287","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}

{"title":"Vibrational Analysis Based on Cavity-Enhanced Raman Spectroscopy: Cyclohexane.","authors":"Qing-Ying Yang, Qin Yang, Yi-Fan Song, An-Wen Liu, Jin Wang, Yan Tan, Yu R Sun, Shui-Ming Hu","doi":"10.1021/acs.jpca.4c07709","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07709","url":null,"abstract":"<p><p>Cyclohexane (CAS: 110-82-7), a colorless organic solvent derived from petroleum, is a valuable reference standard for Raman shift calibration and serves as a model for six-membered ring structures in complex chemical and biological systems. In this study, we measured polarized Raman spectra of gaseous cyclohexane at room temperature using cavity-enhanced Raman spectroscopy (CERS) across the range of 200-3200 cm^-1. The observed vibrational wavenumbers, intensities, and depolarization ratios were compared with calculated values, enabling the assignment of several dozen Raman-active bands, including many overtone and combination bands. This work demonstrates the capability of CERS for vibrational analysis of gas-phase polyatomic molecules.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143750074","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}

{"title":"Identification of the Elusive Methyl-Loss Channel in the Crossed Molecular Beam Study of Gas-Phase Reaction of Dicarbon Molecules (C₂; X¹Σ_g⁺/a³Π_u) with 2-Methyl-1,3-butadiene (C₅H₈; X¹A').","authors":"Iakov A Medvedkov, Zhenghai Yang, Shane J Goettl, Ralf I Kaiser","doi":"10.1021/acs.jpca.5c00639","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c00639","url":null,"abstract":"<p><p>The crossed molecular beam technique was utilized to explore the reaction of dicarbon C₂ (X¹Σ_g⁺/a³Π_u) with 2-methyl-1,3-butadiene (isoprene, CH₂C(CH₃)CHCH₂; X¹A') at a collision energy of 28 ± 1 kJ mol^-1 using a supersonic dicarbon beam generated via photolysis (248 nm) of helium-seeded tetrachloroethylene (C₂Cl₄). Experimental data combined with previous <i>ab initio</i> calculations provide evidence of the detection of the hitherto elusive methyl elimination channels leading to acyclic resonantly stabilized hexatetraenyl radicals: 1,2,4,5-hexatetraen-3-yl (CH₂CC^•CHCCH₂) and/or 1,3,4,5-hexatetraen-3-yl (CH₂CHC^•CCCH₂). These pathways are exclusive to the singlet potential energy surface, with the reaction initiated by the barrierless addition of a dicarbon to one of the carbon-carbon double bonds in the diene. In combustion systems, both hexatetraenyl radicals can isomerize to the phenyl radical (C₆H₅) through a hydrogen atom-assisted isomerization─the crucial reaction intermediate and molecular mass growth species step toward the formation of polycyclic aromatic hydrocarbons and soot.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143735563","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}

{"title":"Teacups, a Python Package for the Simulation of Time-Resolved EPR Spectra of Spin-Polarized Multi-Spin Systems.","authors":"Theresia Quintes, Stefan Weber, Sabine Richert","doi":"10.1021/acs.jpca.5c01512","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c01512","url":null,"abstract":"<p><p>Spin-polarized magnetic systems, generated by the interaction of photoactive molecules with light, play a key role in a wide range of scientific applications. Representative examples are OLEDs, organic photovoltaics, and singlet fission. Further, they are important intermediates in certain biological processes including photosynthesis and, possibly, avian magnetoreception. Transient continuous-wave electron paramagnetic resonance (trEPR) spectroscopy is a powerful tool to reveal the temporal evolution of nonequilibrium spin states, which contains valuable information on any photoinduced dynamic processes occurring in these systems. For the analysis of the recorded trEPR data, simulations are essential. While the simulation of static trEPR spectra is supported well by tools like EasySpin, the simulation of time-resolved trEPR data is less developed. Here, we introduce teacups, a new freely available and well-documented Python-based routine for the simulation of the temporal evolution of trEPR spectra. The internal dynamics of different spin-polarized systems can be analyzed, thereby enhancing our mechanistic understanding. In this manuscript, we explain the theoretical background and provide a description of the features and setup of teacups. Further, a step-by-step example for data analysis is provided.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143727019","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}

{"title":"Comprehensive Insights into Exciplex Behavior in Nonpolar Media: Revisiting Weller's Framework with Molecular Conformation.","authors":"Suhyun Park, Ena Yun, Jong-Won Song, Hohjai Lee","doi":"10.1021/acs.jpca.5c01445","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c01445","url":null,"abstract":"<p><p>Exciplexes are pivotal in organic light-emitting diodes and photovoltaics. However, their formation and emission in nonpolar solvents remain unclear. Revisiting Weller's works on photoinduced electron transfer (PET) rates and exciplex emission based on electrochemical redox potentials, we investigate exciplex behavior in cyclohexane using anthracene (Ant) as an acceptor and <i>N</i>,<i>N</i>-dimethylaniline (DMA) derivatives as donors. Employing steady-state and time-resolved spectroscopy, electrochemistry, and density functional theory (DFT) calculations, we demonstrate that electrochemical redox potentials alone inadequately explain the exciplex behavior in nonpolar environments. Our DFT analysis reveals that the C-N rotational angle of the dimethylamine group of a donor influences the highest occupied molecular orbital (HOMO) energy levels, affecting quenching processes. Furthermore, time-dependent DFT simulations accurately reproduce experimental exciplex emission spectra, linking emission intensity to donor contribution in the exciplex HOMO. These findings deepen the understanding of exciplex behavior in nonpolar media and provide insights for designing and interpreting exciplex-based optoelectronic materials.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143727097","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}

{"title":"Spin-Free Exact Two-Component Linear Response Coupled Cluster Theory for the Estimation of Frequency-Dependent Second-Order Properties.","authors":"Sudipta Chakraborty, Tamoghna Mukhopadhyay, Achintya Kumar Dutta","doi":"10.1021/acs.jpca.4c03584","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c03584","url":null,"abstract":"<p><p>We have presented the theory, implementation, and benchmark results for the one-electronic variant of spin-free exact two-component (SFX2C1e) linear response coupled cluster (LRCCSD) theory for static and dynamic polarizabilities of atoms and molecules in the spin-summed formulation. The resolution of identity (RI) approximation for two-electron integrals has been used to reduce the computational cost of the calculation and has been shown to have a negligible effect on accuracy. The calculated static and dynamic polarizability values agree very well with the more expensive X2C-LRCCSD and the experimental results. Our calculated results show that accurate predictions of polarizabilities of atoms and molecules containing heavy atoms require the use of a large basis set containing an adequate number of diffuse functions, in addition to accounting for electron correlation and relativistic effects.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143727013","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}

{"title":"Quantum Chemical Study on the Evolution of Sulfur Functional Groups during Char Burnout.","authors":"Bastian Schnieder, Rochus Schmid, Christof Hättig","doi":"10.1021/acs.jpca.4c07973","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07973","url":null,"abstract":"<p><p>The oxy-fuel combustion of biochar connected with carbon capture, storage, and utilization technologies is an environmentally beneficial alternative for the replacement of fossil fuels. Biochar itself consists of porously stacked layers of hydrocarbons containing several heteroatoms, such as oxygen, nitrogen, and sulfur. At present, only limited information on the combustion mechanisms for oxygen and nitrogen functionalities is available in the literature; specific information on the combustion mechanisms of sulfur-containing groups (SFGs) is lacking. In this study, we present electronic structure calculations to uncover the mechanisms of the initial oxidation reactions of SFGs. Furthermore, it is examined if the reaction mechanisms remain similar or change with increasing system size. For this purpose, we apply an automatized workflow combining reactive molecular dynamics simulations with static electronic structure calculations at different levels of theory. The results show that terminal groups such as thiols, sulfonic acids, thioketones, and <i>S</i>,<i>S</i>-dioxides follow similar reaction pathways. These SFGs are all gradually oxidized before they eventually are eliminated as SO_<i>x</i>(H_<i>y</i>) species from the carbon framework. Embedded thiophenes follow somewhat different reaction pathways that lead to the elimination of HOS· radicals or carbonyl sulfide (COS), depending on the system size. For the found oxidation channels, we report reaction and activation energies and rate constants that can be used to improve comprehensive kinetic models for the combustion of sulfur-containing biochar as a biomass-based renewable energy source.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143727003","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}

{"title":"Neutral Cyclic Nitreones: Electronic Structure Analysis Reveals an Unorthodox Perspective of Several Zwitterionic Heterocyclic Species.","authors":"Astha Gupta, Pooja Saulanki, Prasad V Bharatam","doi":"10.1021/acs.jpca.4c08235","DOIUrl":"10.1021/acs.jpca.4c08235","url":null,"abstract":"<p><p>Nitreones are compounds with the general formula L → N⁺ ← L'. These compounds exhibit medicinal properties and have found applications in phase transfer catalysis. A few nitreones are cyclic; protonated cycloguanil (an antimalarial agent) is the most prominent example. Recently, a few more cyclic compounds were experimentally reported, in which the central N⁺ was shown to exhibit nitreone character. This led to attention being paid to the chemistry of neutral cyclic nitreones. A thorough literature search led to two sets of cyclic nitreones: C → N ← C type and P → N ← P type. In this work, we report quantum chemical analysis in exploring the electronic structure of neutral cyclic nitreones. Molecular orbital analysis, electron density analysis, charge, electron localization function (ELF), complexation energy values, and Tolman electronic parameter (TEP) all indicate that the studied compounds do carry nitrogen in the N(I) oxidation state and the two lone pairs are at the central nitrogen; thus, they qualify to be considered as cyclic nitreones.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"2854-2865"},"PeriodicalIF":2.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595873","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}

{"title":"Theoretical Investigation on the Reaction Kinetics of OH with Furfural.","authors":"Qiongxuan Zhu, Lili Xing, Zhiyuan Ma, Liuchao Lian, Jing Zhu, Haojie Li, Mengjie Liu, Xuetao Wang","doi":"10.1021/acs.jpca.4c06221","DOIUrl":"10.1021/acs.jpca.4c06221","url":null,"abstract":"<p><p>Furfural is a typical representative molecule of furan compounds and an important intermediate species in the oxidation of furan derivatives. The rate constant of furfural with OH is calculated for the first time using a high-level quantum chemistry method combined with the Rice-Ramsperger-Kassel-Marcus theory/master equation method. The M06-2X/jun-cc-pVTZ method was used to construct the potential energy surface of the reaction path. The preliminary reactions can occur through three different pathways: H-abstraction from the furan ring, H-abstraction from the side chain, and a preliminary OH-addition. The pathways via the OH-addition mechanism of the furfural + OH system were superior to H-abstraction in the temperature range of 298-400 K. When the temperature exceeds 400 K, the H-abstraction will be faster. Moreover, with the increase of pressure, the competition of the pathway via the OH-addition mechanism in the low-temperature region will gradually weaken. Under low-temperature conditions, INT1 and INT4 are the main intermediate species. The formation of bimolecular products, the 2-furanol (P7) + aldehyde group and the (3<i>E</i>)-4-hydroxybuta-1,3-diene-1-one (P8) + aldehyde group at C(2) and C(5) sites, are the main reaction pathways via the OH-addition mechanism. The formation of (2-furanyl)(oxy) methyl (P4) + H₂O (i.e., R4) always dominates for the four H-abstraction reactions. For the initial H-abstraction reaction, there is no pressure dependence, but for the preliminary OH-addition reaction, there is a significant positive pressure dependence. This work not only provides the necessary rate constants for modeling development but also provides theoretical guidance for the practical application of furan-based fuel.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"2932-2945"},"PeriodicalIF":2.7,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143622891","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}