The Journal of Physical Chemistry A最新文献

{"title":"Quadrupole-Central-Transition ²³Na, ³⁹K, ⁸⁷Rb NMR Studies of Alkali Metal Ions under Different Molecular Tumbling Conditions: A Simple Model to Treat Chemical Exchange Involving Quadrupolar Nuclei.","authors":"Ziyao Peng, Gang Wu","doi":"10.1021/acs.jpca.4c07473","DOIUrl":"10.1021/acs.jpca.4c07473","url":null,"abstract":"<p><p>We report a new NMR method for treating two-site chemical exchange involving half-integer quadrupolar nuclei in a solution. The new method was experimentally verified with extensive ²³Na (<i>I</i> = 3/2), ³⁹K (<i>I</i> = 3/2), and ⁸⁷Rb (<i>I</i> = 3/2) NMR results from alkali metal ions (Na⁺, K⁺, and Rb⁺) in a solution over a wide range of molecular tumbling conditions. In the fast-motion limit, all allowed single-quantum NMR transitions for a particular quadrupolar nucleus are degenerate giving rise to one Lorentzian signal. In the slow-motion regime, although the NMR signal from quadrupolar nuclei should in principle exhibit a multi-Lorentzian line shape, only the quadrupole central transition (QCT) is often detectable in practice. In all the cases studied in this work, we found that alkali metal ions undergo fast exchange between free and bound states. Using the new theoretical method, we were able to interpret the experimental transverse relaxation data (i.e., line widths) obtained for ²³Na, ³⁹K, and ⁸⁷Rb NMR signals including QCT signals over a large temperature range and extract information about ion-binding dynamics in different chemical environments. This work fills a gap in the literature where a unified approach for treating NMR transverse relaxation data for quadrupolar nuclei over the entire range of motion has been lacking. Our results suggest that the new approach is applicable in the study of alkali metal ion binding to biological macromolecules.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"803-813"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941499","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 Investigations on the Molecular Magnetic Behavior of Actinide Molecules [AnPc₂]^0/- (An = U, Cf): Prediction of the High Magnetic Blocking Barrier and Magnetic Blocking Temperature in [CfPc₂]<sup />.","authors":"Jie Liu, Yaqing Chen, Huan Tang, Hong Chen, Ruizhi Qiu, Hongkuan Yuan","doi":"10.1021/acs.jpca.4c06757","DOIUrl":"10.1021/acs.jpca.4c06757","url":null,"abstract":"<p><p>Searching for single-molecule magnets (SMM) with large effective blocking barriers, long relaxation times, and high magnetic blocking temperatures is vitally important not only for the fundamental research of magnetism at the molecular level but also for the realization of new-generation magnetic memory unit. Actinides (An) atoms possess extremely strong spin-orbit coupling (SOC) due to their 5<i>f</i> orbitals, and their ground multiplets are largely split into several sublevels because of the strong interplay between the SOC of An atoms and the crystal field (CF) formed by ligand atoms. Compared to TM-based SMMs, more dispersed energy level widths of An-based SMMs will give a larger total zero field splitting (ZFS) and thus provide a necessary condition to derive a higher <i>U</i>_eff. In combination of the density functional theory (DFT) as well as the CF model Hamiltonian and <i>ab initio</i> calculation, we have investigated the structural stability and electronic structures as well as the magnetodynamic behavior of [AnPc₂]^0/- (An = U, Cf) molecules. We find that An atoms can strongly interact with its ligand N atoms in forming An-N ionic bonds, and 5<i>f</i> electrons are more localized in the Cf atom than in the U atom, giving U⁴⁺(5f²) and Cf³⁺(5f⁹) valence states. Although the UPc₂ molecule has a modest value of <i>U</i>_eff = 514 cm^-1, it is not a good SMM due to the easy occurrence of quantum tunneling of magnetization (QTM). Based on the consistent results of CF Hamiltonian and <i>ab initio</i> calculations on the [CfPc₂]^- molecule, we propose that almost prohibited QTM within the Kramers doublets (KDs) as well as very low transition probabilities between different states via hindered spin-flip transitions would result in a high <i>U</i>_eff = 1401 cm^-1. The estimated high magnetic blocking temperature (<i>T</i>_B) of 58 K renders [CfPc₂]^- an excellent SMM candidate, implying that magnetic hysteresis could be observed in future experiments.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"717-732"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941515","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":"Spatial Signatures of Electron Correlation in Least-Squares Tensor Hypercontraction.","authors":"Chao Yin, Sara Beth Becker, James H Thorpe, Devin A Matthews","doi":"10.1021/acs.jpca.4c06666","DOIUrl":"10.1021/acs.jpca.4c06666","url":null,"abstract":"<p><p>Least-squares tensor hypercontraction (LS-THC) has received some attention in recent years as an approach to reduce the significant computational costs of wave function-based methods in quantum chemistry. However, previous work has demonstrated that LS-THC factorization performs disproportionately worse in the description of wave function components (e.g., cluster amplitudes <i>T̂</i>₂) than Hamiltonian components (e.g., electron repulsion integrals (<i>pq</i>|<i>rs</i>)). This work develops novel theoretical methods to study the source of these errors in the context of the real-space <i>T̂</i>₂ kernel, and reports, for the first time, the existence of a \"correlation feature\" in the errors of the LS-THC representation of the \"exchange-like\" correlation energy <i>E</i>_<i>X</i> and <i>T̂</i>₂ that is remarkably consistent across ten molecular species, three correlated wave functions, and four basis sets. This correlation feature portends the existence of a \"pair point kernel\" missing in the usual LS-THC representation of the wave function, which critically depends upon pairs of grid points situated close to atoms and with interpair distances between one and two Bohr radii. These findings point the way for future LS-THC developments to address these shortcomings.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"788-802"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941505","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 Study on the Kinetics of Secondary Oxygen Addition Reactions for N-Butyl Radicals.","authors":"Xiaojun Zhou, Le Li, Jie Xue, Fan Wang, Xiao He","doi":"10.1021/acs.jpca.4c07506","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07506","url":null,"abstract":"<p><p>Chemical kinetics for second oxygen addition reactions (·QOOH + O₂) of long-chain alkanes are of great importance in low-temperature combustion technologies. However, kinetic data for key reactions of ·QOOH + O₂ systems are often difficult to obtain experimentally and are primarily estimated or calculated by using theoretical methods. In this work, barrier heights (BHs), reaction energies (Δ<i>E</i>s), and relative energies (REs) of stationary points for key reactions of two representative ·QOOH + O₂ systems in the low-temperature oxidation of <i>n</i>-butyl as well as pressure-dependent rate constants for the involved reactions are calculated with the high-level quantum chemical method CCSD(T)-F12b/CBS. These results can be employed in the development of low-temperature combustion mechanisms for <i>n</i>-butane and longer straight-chain alkanes. In addition, the performance of some quantum chemistry methods with a lower computational cost on BHs, Δ<i>E</i>s, and REs as well as rate constants is also investigated. Our results indicate that the maximum error on these energies with PNO-LCCSD(T)-F12a is within 1 kcal/mol, and rate constants with this method are in the best agreement with reference values, with a maximum relative error of about half the reference values. Due to its low computational cost and memory requirements, this method is strongly recommended for studying low-temperature combustion reactions involving larger hydrocarbon fuels.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021253","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":"Side-On Bound Beryllium Dinitrogen Complex: A Precursor for Complete Conversion of Dinitrogen to Ammonia Mediated by <i>N</i>-Heterocyclic Carbene.","authors":"Siddhartha K Purkayastha, Ankur K Guha","doi":"10.1021/acs.jpca.4c06738","DOIUrl":"10.1021/acs.jpca.4c06738","url":null,"abstract":"<p><p>The complete conversion of dinitrogen to ammonia mediated by a side-on N₂-bound carbene-beryllium complex, [NHC-Be(η²-N₂)] has been studied considering both the symmetric and unsymmetric pathways. <i>N</i>-heterocyclic carbenes complexed with Be(η²-N₂) moieties were considered substrates in our study. We found that two mechanistic pathways were possible for the reduction of dinitrogen to form ammonia. Our calculations revealed that the symmetric pathway is more favorable compared to the unsymmetric one. The interconversion of the complex from the symmetric product to the unsymmetric one involves a large activation energy barrier for the proton transfer pathway. Both of these pathways were associated with high exergonicity, and the N-N bond is observed to be elongated, which indicates that the NHC-Be(η²-N₂) complex is a promising candidate for dinitrogen activation and subsequent reduction, resulting in the formation of ammonia. The bonding scenario of the NHC-Be(η²-N₂) complex can be explained well by the famous Dewar-Chatt-Duncanson (DCD) model. Our calculations reveal that the symmetric pathway is found to be more suitable due to more negative values of change in Gibbs free energy. Solvent phase calculations have identified the viability of the NHC-Be(η²-N₂) complex, indicating that the complex is sustainable in low-polar organic solvents, such as toluene and diethyl ether.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"705-716"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941501","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":"Acid-Base Equilibrium of 5,5,6-Trihydroxy-6-Methyldihydropyrimidine-2,4(1<i>H</i>,3<i>H</i>)-Dione in the Gas Phase and in Water.","authors":"Svetlana F Petrova, Edward M Khamitov, Timur R Nugumanov, Sergey P Ivanov","doi":"10.1021/acs.jpca.4c05989","DOIUrl":"10.1021/acs.jpca.4c05989","url":null,"abstract":"<p><p>The first-stage acid-base equilibrium of 5,5,6-trihydroxy-6-methyldihydropyrimidine-2,4(1<i>H</i>,3<i>H</i>)-dione was studied for the first time in aqueous solutions. Its constant (pK_a1 = 9.23 ± 0.03) and thermodynamic parameters (Δ<i>G</i>₂₉₈ = 52 ± 1 kJ·mol^-1, Δ<i>H</i> = 83 ± 1 kJ·mol^-1, and Δ<i>S</i>₂₉₈ = 103 ± 4 J·mol^-1·K^-1) were determined by potentiometric titration. Computational analysis, including molecular dynamics (MD) simulations and quantum chemical calculations, was conducted to evaluate solvation effects and proton dissociation sites. MD simulations identified distinct solvation shells and interactions with water molecules, while quantum chemical calculations highlighted the primary deprotonation site. Fuzzy bond order (FBO) analysis and energy calculations of anionic forms corroborated these findings, demonstrating a strong correlation between the Δ<i>E</i> and FBO values. The research established the dissociation sequence for conformational <i><b>R</b></i>- and <i><b>S</b></i>-isomers of the title compound and validated the FBO method as an efficient tool for assessing dissociation processes in polybasic acids.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"661-666"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968742","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":"Correction to \"Leveraging Machine Learning To Predict the Atmospheric Lifetime and the Global Warming Potential of SF6 Replacement Gases\".","authors":"Guobin Zhao, Haewon Kim, Changwon Yang, Yongchul G Chung","doi":"10.1021/acs.jpca.5c00016","DOIUrl":"10.1021/acs.jpca.5c00016","url":null,"abstract":"","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"814"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142941470","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 Study on the Internal Conversion Decay Pathways of Bithiophene-Fused Isoquinolines.","authors":"Takeshi Yoshikawa, Atsuya Inoue, Kaito Aoyama, Yasuhiro Ikabata, Takahiro Sawano, Ryo Takeuchi, Ken Sakata","doi":"10.1021/acs.jpca.4c07552","DOIUrl":"10.1021/acs.jpca.4c07552","url":null,"abstract":"<p><p>In this study, the radiative and nonradiative decay pathways from the first singlet excited states (denoted as S₁) of three bithiophene-fused isoquinolines were investigated by using the mixed-reference spin-flip time-dependent density functional theory approach. These isoquinolines, which are prepared via [2 + 2 + 2] cycloaddition reactions between three types of bithiophene-linked diynes and nitriles, exhibit different fluorescence quantum yields in response to the positions of their sulfur atoms. The decay processes, including the fluorescence emission and internal conversion, were considered. In the internal conversion pathway, the minimum energy conical intersection structures between the ground and first singlet excited states (denoted as S₀/S₁ MECI) of the ring strain for the isoquinoline skeleton and the ring opening of the thiophene skeleton were systematically explored. Dewar-type ring strain resulted in the smallest energy barrier from the equilibrium geometries of the ground state (denoted as S₀) to the MECI structures between the S₀ and S₁ states. The energy difference between the three types of bithiophene-fused isoquinolines at the transition state geometries of the S₁ state varies owing to the steric effects between the methyl groups and the hydrogen atom of the thiophene ring, and the excitation energy increases owing to a decrease in aromaticity. In addition, the oscillator strengths of the S₀ and S₁ states were evaluated at the equilibrium geometries of the S₁ state to determine the contribution of the fluorescence process. The obtained theoretical results are consistent with the experimental results.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"744-753"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142963379","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":"Structural Changes in Metal Chalcogenide Nanoclusters Associated with Single Heteroatom Incorporation.","authors":"Xilai Li, Shana Havenridge, Habib Gholipour-Ranjbar, Dylan Forbes, Wyatt Crain, Cong Liu, Julia Laskin","doi":"10.1021/acs.jpca.4c07000","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07000","url":null,"abstract":"<p><p>Atomically precise nanoclusters (NCs) are promising building blocks for designing materials and interfaces with unique properties. By incorporating heteroatoms into the core, the electronic and magnetic properties of NCs can be precisely tuned. To accurately predict these properties, density functional theory (DFT) is often employed, making the rigorous benchmarking of DFT results particularly important. In this study, we present a benchmarking approach based on metal chalcogenide NCs as a model system. We synthesized a series of bimetallic, iron-cobalt chalcogenide NCs [Co_6-<i>x</i>Fe_<i>x</i>S₈(PEt₃)₆]⁺ (<i>x</i> = 0-6) (PEt = triethyl phosphine) and investigated the effect of heteroatoms in the octahedral metal chalcogenide core on their size and electronic properties. Using ion mobility-mass spectrometry (IM-MS), we observed a gradual increase in the collision cross section (CCS) with an increase in the number of Fe atoms in the core. DFT calculations combined with trajectory method CCS simulations successfully reproduced this trend, revealing that the increase in cluster size is primarily due to changes in metal-ligand bond lengths, while the electronic properties of the core remain largely unchanged. Moreover, this method allowed us to exclude certain multiplicity states of the NCs, as their CCS values were significantly different from those predicted for the lowest-energy structures. This study demonstrates that gas-phase IM-MS is a powerful technique for detecting subtle size differences in atomically precise NCs, which are often challenging to observe using conventional NC characterization methods. Accurate CCS measurements are established as a benchmark for comparison with theoretical calculations. The excellent correspondence between experimental data and theoretical predictions establishes a robust foundation for investigating structural changes of transition metal NCs of interest to a broad range of applications.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143021251","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":"Insight into the Excited States in Monomers and π-Stacked Dimers of Azulene-Fused Acenes: ADC(2) and TD-DFT Studies.","authors":"Palak Mandal, Aditya N Panda","doi":"10.1021/acs.jpca.4c08515","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c08515","url":null,"abstract":"<p><p>Charge transfer (CT) states in polycyclic aromatic hydrocarbons play crucial roles in determining their electronic properties and their potential applications in organic electronics. In this work, we investigate the nature of the excited states in monomers and π-stacked dimers of azulene-fused naphthalene and anthracene systems, focusing on the interplay between structure and excited-state properties. Four different isomers for azulene-fused naphthalene (<b>NapAz-A</b>, <b>NapAz-B</b>, <b>NapAz-C</b>, and <b>NapAz-D</b>) and anthracene (<b>AntAz-A</b>, <b>AntAz-B</b>, <b>AntAz-C</b>, and <b>AntAz-D</b>) are considered. The excited-state studies are performed at the SCS-ADC(2) level and at the TD-DFT level using CAM-B3LYP, SCS-ωB2GP-PLYP, and SCS-RSX-QIDH functionals. For the monomers, the SCS-ADC(2) results reveal that states with CT characters are different in naphthalene- and anthracene-based systems. In π-stacked dimers, a few of the excited states are of the charge resonance (CR) type in <b>NapAz-A</b>, <b>NapAz-B</b>, and <b>NapAz-C</b> and the intermolecular CT type in <b>NapAz-D</b>. Similarly, <b>AntAz-A</b>, <b>AntAz-B</b>, and <b>AntAz-D</b> have some CR type excited states, whereas the <b>AntAz-C</b> isomer has intramolecular CT type excited states. Overall, among the three DFT functionals considered, CAM-B3LYP has been found to reproduce well the SCS-ADC(2) excited results in both monomers and π-stacked dimers.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996331","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}