The Journal of Physical Chemistry A最新文献

{"title":"Excited-State H-Aggregation Enables Proton Abstraction from Water in Weak Photobases","authors":"Jiawen Fang*,&nbsp;Qinxiang Huang,&nbsp;Ping Li,&nbsp;Enyi Lan,&nbsp;Kang Shen* and Chaochao Qin*,&nbsp;","doi":"10.1021/acs.jpca.5c0177810.1021/acs.jpca.5c01778","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c01778https://doi.org/10.1021/acs.jpca.5c01778","url":null,"abstract":"<p >Photobasic molecules can abstract a proton from water in the picosecond range, enabling efficient photochemical reactions, especially photocatalytic water splitting. However, such molecules are rarely reported due to the challenge of achieving an excited-state p<i>K</i>_a (p<i>K</i>_a*) close to the p<i>K</i>_a of water ( 15.7). Here, we demonstrate that excited-state H-aggregation can substantially enhance proton-attracting capability by raising the energy of unprotonated species. According to the Förster cycle, the thermodynamic driving force for proton attraction is determined by the energy difference between the protonated and unprotonated species. For the model weak photobasic molecule citrazinic acid, excited-state H-aggregates are formed simply by adjusting the concentration. The energy of the unprotonated species increases by 0.38 eV upon aggregation, while that of the protonated species remains unchanged. The increased energy difference significantly increases the p<i>K</i>_a* from a ground-state value of 2.5 to 15.4. Consequently, the weak photobasic aggregates are enabled to abstract a proton from water, a capability absent in the isolated form. Meanwhile, the lower-energy state in H-aggregates functions as a rate-limiting intermediate state, delaying the proton transfer dynamics, but the delay can be modulated by the excitation wavelength. This work provides fundamental insights into H-aggregation-induced photobasicity, opening new avenues for modulating photochemical reactions simply through concentration and light.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"129 21","pages":"4673–4681 4673–4681"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144166038","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":"Astrochemical Significance of C2H7NO Isomers: A Computational Perspective on Their Stability and Detectability","authors":"Lisset Noriega*,&nbsp;Luis Armando Gonzalez-Ortiz,&nbsp;Filiberto Ortíz-Chi and Gabriel Merino*,&nbsp;","doi":"10.1021/acs.jpca.5c0108610.1021/acs.jpca.5c01086","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c01086https://doi.org/10.1021/acs.jpca.5c01086","url":null,"abstract":"<p >Nitrogen- and oxygen-containing molecules play a key role in interstellar chemistry, particularly as precursors to biologically relevant species such as amino acids. Among the C₂H₇NO isomers, 2-aminoethanol is the only one detected in the ISM. This study systematically explores the C₂H₇NO chemical space, identifying eight structural isomers, with 1-aminoethanol as the global minimum and methylaminomethanol, 11.5 kcal/mol higher in energy, as a viable higher-energy species. To assess their astrochemical relevance, we conducted a comprehensive conformational analysis and computed rotational constants to guide future spectroscopic searches. These findings provide critical insights into C₂H₇NO isomers, identifying new candidates for ISM detection and expanding our understanding of nitrogen- and oxygen-containing organic species in space.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"129 21","pages":"4715–4723 4715–4723"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.jpca.5c01086","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144166036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Introduction to Relativistic Electronic Structure Calculations.","authors":"Donald G Truhlar, Xiaosong Li","doi":"10.1021/acs.jpca.5c00859","DOIUrl":"10.1021/acs.jpca.5c00859","url":null,"abstract":"<p><p>It is important to include relativistic effects in electronic structure calculations for many important chemical problems, including heavy-element chemistry, intersystem crossing, and zero-field splitting. The subject is old, but recent developments have been rapid. The specialized literature can be daunting for nonspecialists, and this article is intended to provide an entry to that literature, especially for the modern treatment of molecules. There are only five equations. We include discussion of the relations between four-component, two-component, and one-component treatments, the distinction between scalar relativistic effects and angular-momentum-dependent effects, approximate treatments of spin-orbit coupling, including the molecular mean-field approximations, the inclusion of electron correlation in relativistic wave functions, and zero-field splitting.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4301-4312"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143955659","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 Spin Transport Through Blatter's Diradicals and Triradicals.","authors":"Ashima Bajaj, Shahjad Ali, Rishu Khurana, Md Ehesan Ali","doi":"10.1021/acs.jpca.4c08702","DOIUrl":"10.1021/acs.jpca.4c08702","url":null,"abstract":"<p><p>A single unpaired electron in an organic molecule residing in the singly occupied molecular orbital (SOMO) renders it an organic radical. It incorporates exchange splitting in the frontier occupied and unoccupied orbitals, separating the α- and β-orbitals. This fact enormously impacts the electron transport properties in organic radicals by promoting spin-polarized current and significantly enhancing conductance compared to their closed-shell counterparts. Exploring these phenomena, several monoradicals have been investigated through molecular spintronic experiments and theories. In this work, we addressed the impact of an increasing number of radical centers on the transport properties of multiradical molecular species by considering di- and triradicals based on a stable Blatter's radical. With an increasing number of radical centers, the number of SOMOs increases. Does the increased number of frontier SOMOs provide larger exchange splitting and better transport properties? Here, we observed that the spatial distributions of SOMOs and their coupling with electrodes play a decisive role compared with the presence of multiple unpaired electrons in the molecular systems.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4252-4264"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143951310","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":"Vibrationally Resolved Photoelectron Spectroscopy and Quantum Chemical Calculations of InC_<i>n</i>^- (<i>n</i> = 3-10) Clusters.","authors":"Zhao-Ou Gao, Zhen-Chao Long, Hong-Guang Xu, Sheng-Jie Lu, Xi-Ling Xu, Wei-Jun Zheng","doi":"10.1021/acs.jpca.5c00496","DOIUrl":"10.1021/acs.jpca.5c00496","url":null,"abstract":"<p><p>The vibrationally resolved photoelectron spectra of InC_<i>n</i>^- (<i>n</i> = 3-10) clusters were measured using size-selected anion photoelectron spectroscopy. The structures of InC_<i>n</i>^-/0 (<i>n</i> = 3-10) clusters were investigated through quantum chemical calculations. A pronounced odd-even alternation in vertical detachment energies (VDEs) of InC_<i>n</i>^- (<i>n</i> = 3-10) is observed as the carbon chain length increases. The InC_<i>n</i>^- (<i>n</i> = 4, 6, 8, and 10) anions exhibit higher VDEs than their adjacent anions with odd carbon numbers. The most stable structures of InC_<i>n</i>^- and InC_<i>n</i> (<i>n</i> = 3-10) adopt <i>C</i>_∞v symmetric linear structures with the indium atom located at the end of the carbon chain, except for InC₁₀. InC₁₀ exhibits a C₁₀ ring structure with the indium atom bonding externally to one carbon atom, which is slightly more stable than the linear structure. Bonding analysis reveals the monovalent nature of the indium atom and the covalent character of the In-C bond. Finally, the limitations of the CCSD(T) method in achieving high-accuracy calculations for this system are discussed.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4204-4216"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143951368","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":"Electron Spin Resonance Study of Radicals Produced from Organic Triplet Excited States in Photolyzed Aqueous Mixtures.","authors":"Maria Misovich, Hannah Folarin, Suranjan K Paul, Ryan Walter, R Michael Everly, Jonas Baltrusaitis, Lyudmila V Slipchenko, Alexander Laskin","doi":"10.1021/acs.jpca.4c08458","DOIUrl":"10.1021/acs.jpca.4c08458","url":null,"abstract":"<p><p>Photochemically produced triplet excited states of organic matter (³C*) play a crucial role in establishing free radical pools that drive oxidation chemistry in atmospheric and terrestrial water systems. Chemical characterization and quantitative speciation of these free radical mixtures are challenging due to their short lifetimes and the inherent complexity of the mixtures. In this study, we demonstrate the use of electron paramagnetic resonance (EPR) spectroscopy, assisted with the spin trap reagent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), to measure concentrations of free radicals initiated by ³C* formed through the photoexcitation of 3,4-dimethoxybenzaldehyde (DMB). We evaluate the background radical contributions from the photolysis of aqueous DMPO under various conditions of single-wavelength and broadband irradiation. Subsequently, we characterize and quantify the DMPO-trapped radical products produced in irradiated aqueous mixtures containing DMB, struvite microcrystal colloids, and a mixture of both DMB and struvite, serving as environmentally relevant proxies. The identified DMPO-trapped radical products include the spin adduct with hydroxyl (^·OH) radicals (DMPO-OH), the spin adduct with hydrogen (^·H) radicals (DMPO-H), the DMPO dimer radical, and the oxidation product DMPOX. Among these, DMPO-OH was found to exist at the highest concentration. The concentration of DMPO products increased linearly with ³C* concentration up to 50 μM, with DMPO-OH existing in the highest concentration. Struvite microcrystals were observed to influence the relative proportions of the DMPO products, altering the radical pool composition. Our experimental observations and computational studies of DMPO excitation energies in an aqueous environment revealed its photolytic lability under irradiation with wavelengths of 365 nm or shorter. These findings indicate the necessity of accounting for background photolysis reactions of DMPO to avoid overestimating radical concentrations during quantitative EPR studies. This work provides valuable insights into the mechanisms of free radical formation mediated by ³C* and evaluates the utility and limitations of DMPO as a tool for investigating complex aqueous photochemical radical systems.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4265-4274"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143956085","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":"Recursion Equations in Polycyclic Hydrocarbon Series and the Number of Dewar Long-Bond Resonance Structures with Applications.","authors":"Jerry Ray Dias","doi":"10.1021/acs.jpca.5c01651","DOIUrl":"10.1021/acs.jpca.5c01651","url":null,"abstract":"<p><p>Basic recursion equations for characteristic and matching polynomials and the number of Dewar resonance structures for polycyclic polyene series are derived. Fibonacci-like series of numbers frequently appear in recursion and analytical expressions for determining resonance energy terms for polycyclic polyene series successively built up by given Aufbau units. Linear polycyclic polyene series built up from given Aufbau units usually give analytical expressions for determining their resonance energy terms. Polycyclic polyene series with all fixed pπ bonds (<b><i>K</i></b> = 1) have some aromatic stabilization energy as measured by topological resonance energy (TRE), which is explained by the appearance of sextet and larger aromatic circuits in some of their Dewar resonance structures (<i>DS</i>); note that <i>DS</i> can be read as singular (Dewar structure) or plural (Dewar structures) depending on the context. It is demonstrated that a finer evaluation of relative resonance energy and aromaticity requires the inclusion of both Dewar structures (<i>DS</i>) and Kekulé structures (<b><i>K</i></b>). In the valence-bond determination of bond lengths and aromaticity of polycyclic conjugated systems with fixed single and double bonds, the inclusion of Dewar resonance structures is required. Topological conjugation energy (TCE) for all series, whether they have all fixed pπ double bonds (<b><i>K</i></b> = 1) or numerous Kekulé resonance structures (<b><i>K</i></b> > 1), is very similar.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4234-4244"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143951293","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":"Time-Dependent Particle-Breaking Hartree-Fock Model for Electronically Open Molecules.","authors":"Jacob Pedersen, Bendik Støa Sannes, Regina Paul Née Matveeva, Sonia Coriani, Ida-Marie Høyvik","doi":"10.1021/acs.jpca.5c00810","DOIUrl":"10.1021/acs.jpca.5c00810","url":null,"abstract":"<p><p>We develop the time-dependent particle-breaking Hartree-Fock (TDPBHF) model to describe excited states and linear response properties of electronically open molecules. This work represents the first step toward building a wave function-based response theory framework for electronically open quantum systems equivalent to that of closed quantum systems. In the limit of particle conservation, TDPBHF reduces to standard time-dependent Hartree-Fock theory. We illustrate the TDPBHF model by computing valence absorption spectra and frequency-dependent electric dipole polarizabilities for a set of small- to medium-sized organic molecules. The particle-breaking interactions are observed to nonuniformly redshift the excitation energies and induce qualitative changes in the absorption profile. In addition, the mixing of multiple excitations in the TDPBHF wave function is observed to dampen the divergence of the response function in the vicinity of resonance energies.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"4288-4300"},"PeriodicalIF":2.7,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12086847/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143952975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evans–Polanyi-like Formulations for Rapidly Predicting Key Depolymerization Barriers in Xylopyranoses: Toward the Faster Development of Kinetic Models for Hemicellulose Pyrolysis","authors":"Leandro Ayarde-Henríquez*,&nbsp;Jacopo Lupi,&nbsp;Bernardo Ballotta and Stephen Dooley,&nbsp;","doi":"10.1021/acs.jpca.5c0067510.1021/acs.jpca.5c00675","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c00675https://doi.org/10.1021/acs.jpca.5c00675","url":null,"abstract":"<p >This work elucidates Evans–Polanyi-like (EPL) relations to rapidly estimate the standard activation enthalpy of three ubiquitous reaction classes playing a central role in hemicellulose pyrolysis: ring-opening, ring contraction, and elimination. These models bypass computing the reaction enthalpy by leveraging computationally cheap local and global electron-density-based chemical reactivity descriptors, such as Fukui’s functions (<i>f</i>), electron population of C–O bonds (<i>N</i>), and the gross intrinsic strength bond index (Δ<i>g</i>^pair), evaluated for reactants solely. More than 270 reactions observed in twenty-eight functionalized β-<span>d</span>-xylopyranoses, the hemicellulose building block, are used under the 20–80% partition scheme for validating-deriving purposes. By using multilinear regression analysis, four EPL equations are proposed for informing barriers at the M06–2X/6–311++G(d,p), CBS-QB3, G4, and DLPNO–CCSD(T)-F12/cc-pVTZ-F12//M06–2X/6–311++G(d,p) levels. An adjusted coefficient of determination of 0.80 characterizes these parametric polynomials. Moreover, MAE and RMSE of ≈3.3 and ≈4.1 kcal mol^–1 describe the performance of the best-fitting models at DFT and G4. Conversely, the highest values, MAE = 3.6 and RMSE = 4.7 kcal mol^–1, are associated with the CBS-QB3 level. The benchmarking of the computed activation enthalpies at 298 K yields simple functions for high-level estimations from low levels of theory with <i>R</i>² ranging from 0.94 to 0.98. Extrapolating the DPLNO barriers to the complete basis set limit tends to lower them by 0.63 kcal mol^–1. EPL expressions are tailored to facilitate the development of chemical kinetic models for hemicellulose pyrolysis, as the reactant structure is the only input required.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"129 21","pages":"4767–4785 4767–4785"},"PeriodicalIF":2.7,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.jpca.5c00675","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144165835","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydration and Conformation of 2-Ethylfuran Explored by Microwave Spectroscopy","authors":"Charlotte N. Cummings,&nbsp; and ,&nbsp;Nicholas R. Walker*,&nbsp;","doi":"10.1021/acs.jpca.5c0128110.1021/acs.jpca.5c01281","DOIUrl":"https://doi.org/10.1021/acs.jpca.5c01281https://doi.org/10.1021/acs.jpca.5c01281","url":null,"abstract":"<p >Rotational spectra of one conformer of a 2-ethylfuran···H₂O complex and two conformers of the isolated 2-ethylfuran molecule have been recorded by chirped-pulse Fourier transform microwave spectroscopy. The species were probed while entrained within a gas sample undergoing supersonic expansion. The spectra of five isotopologues of the complex have been analyzed to yield rotational (<i>A</i>₀, <i>B</i>₀, <i>C</i>₀) and centrifugal distortion constants (<i>D</i>_<i>J</i>, <i>D</i>_<i>JK</i>, <i>d</i>₁) allowing structural parameters to be determined by fitting to the experimentally determined moments of inertia. Quantum chemical calculations have been performed to support the interpretation of the experimental results and gain further insights. 2-Ethylfuran is shown to adopt C₁ symmetry within the observed conformer of 2-ethylfuran···H₂O with the length of the hydrogen bond, <i>r</i>(H_b···O1), which connects H₂O with 2-ethylfuran determined to be 2.0950(42) Å in the <i>r</i>₀ geometry. The geometry of the hydrogen bonding interaction deviates from linearity such that the ∠(O_w–H_b···O1) angle (where O_w and O1 are the oxygen atoms of water and furan, respectively) is 167.69(16)° in the <i>r</i>₀ geometry. The experimental and theoretical results thus imply the presence of a weak interaction between the oxygen of H₂O and the ethyl group within the observed conformer of 2-ethylfuran···H₂O. Evidence is presented to suggest that the C_s conformer of the isolated 2-ethylfuran molecule is lower in energy than the C₁ conformer implying that the energy ordering of the two lowest-energy conformers of 2-ethylfuran reverses when the isolated molecule is hydrated by a single H₂O molecule.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":"129 21","pages":"4644–4653 4644–4653"},"PeriodicalIF":2.7,"publicationDate":"2025-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acs.jpca.5c01281","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144165838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}