The Journal of Physical Chemistry A最新文献

{"title":"Role of the Radical Character in Singlet Fission: An Ab Initio and Quantum Chemical Topology Analysis.","authors":"Karin S Thalmann, Kalith M Ismail, R K Kathir, Diogo J L Rodrigues, Michael Thoss, Ángel Martín Pendás, Pedro B Coto","doi":"10.1021/acs.jpca.4c06380","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06380","url":null,"abstract":"<p><p>The radical character of molecules exhibiting singlet fission is related to the energy level matching relationships that facilitate this process. Using a linear H₄ model molecule, we employ quantum chemical topology descriptors based on full configuration interaction calculations to rationalize singlet fission. In this context, the influence of the closed-shell to diradical and diradical to tetraradical character on the singlet fission energy matching conditions is analyzed. We find that in the diradical limit the singlet fission efficiency can be manipulated considering the active molecule coupled to an excited diradical, while in the diradical to tetraradical limit, the efficiency is dependent only on the gap between the lowest-lying excited singlet and triplet state. Furthermore, our results reveal possible design strategies for molecules with radical character exhibiting efficient singlet fission.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845316","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":"Physical Adsorption and Raman Spectra of Hydrazine Hydrate on the Graphene Surface.","authors":"Zu-Ming Li, Yu-Jun Zhao, Ji-Hai Liao, Jiang Zhang","doi":"10.1021/acs.jpca.4c07193","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07193","url":null,"abstract":"<p><p>In experimental studies, hydrazine hydrate is widely employed as a reducing agent for the conversion of graphene oxide to graphene. Herein, we conducted theoretical calculations using cluster models to investigate the adsorption behavior of hydrazine hydrate on the surface of graphene. The calculated adsorption energy reveals that hydrazine hydrate can physically bind to the graphene surface. Our findings indicate that two hydrogen bonds stabilize the hydrazine hydrate molecule, while its adsorption onto the graphene surface is primarily driven by van der Waals forces. By combining computational simulations and experimental measurements, we thoroughly examined the Raman spectra of both free and adsorbed hydrazine hydrates, which enabled us to gain detailed insights into their molecular vibrations. Notably, in the Raman spectra of free hydrazine hydrate, a strong peak at around 3300 cm^-1 corresponds to the NH₂ vibration. Similarly, peaks near 3300 cm^-1 were observed in the Raman spectra of graphene with adsorbed hydrazine hydrate molecules. The results are expected to provide valuable references for future experimental investigations involving hydrazine hydrate.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142851644","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":"Predicting Rate Constants of Hydrogen Abstraction Reactions between OH/HO₂ and Alkanes by Machine Learning Models.","authors":"Min Xia, Yu Zhang, Hongwei Song, Ya Jia, Minghui Yang","doi":"10.1021/acs.jpca.4c07426","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07426","url":null,"abstract":"<p><p>The hydrogen abstraction reactions by small radicals from fuel molecules play an important role in the oxidation of fuels. However, experimental measurements and/or theoretical calculations of their rate constants under combustion conditions are very challenging due to their high reactivity. Machine learning offers a promising approach to predicting thermal rate constants. In this work, three machine learning methods, XGB, FNN, and XGB-FNN hybrid algorithms, were employed to train and predict the rate constants of the hydrogen abstraction reactions between alkanes and OH/HO₂. Six descriptors were selected according to the Pearson correlation coefficients, the importance of descriptors, and the clustering heat map. It was proven that the XGB-FNN model is the most robust. The constructed XGB-FNN model achieved an average deviation of 89.13% for the alkanes + OH reactions and 190.93% for the alkanes + HO₂ reactions on their respective prediction sets. The model was also used to predict the rate constants of the reactions involving larger alkanes, demonstrating its extrapolation capability. Furthermore, the model has the ability to distinguish the reactivity of the reactions with the hydrogen atom abstracted at different sites of alkane.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142851647","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":"Microsolvation-Driven Hours-Long Spectral Dynamics in Phenoxazine Dyes.","authors":"Ritu Kumari, Vineeta Chaturvedi, Mudit Pithi, Avik K Pati","doi":"10.1021/acs.jpca.4c06314","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06314","url":null,"abstract":"<p><p>The phenoxazine class of dyes has found widespread applications in chemistry and biology for more than a century, particularly for lipid membrane studies. Here, we report a general phenomenon on the ensemble spectral stability of traditional phenoxazine class of dyes (nile red, cresyl violet, and nile blue) that exhibit hours-long microstructural transitions reflected through systematic changes of electronic spectra over an hour. Mechanistic investigations reveal that such spectral dynamics of the dyes can be mitigated by tuning microenvironments, where microsolvation plays an underlying role. These microsolvation-induced microstructural changes in a single dye species tend to follow zeroth-order kinetics. The half-life values of such processes systematically vary with solvent hydrogen bonding strength and ionic radius of the dyes' counteranions. In so doing, using a model lipid membrane, we demonstrate that the spectral response of a phenoxazine dye must be utilized appropriately for studying membrane properties. These findings of the phenoxazine class of dyes are of high significance for their careful applications in chemistry and biology.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833160","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":"Spectroscopy and Excited-State Dynamics of Methyl Ferulate in Molecular Beams.","authors":"Ivan Romanov, Yorrick Boeije, Josene M Toldo, Marianna T Do Casal, Mario Barbatti, Wybren Jan Buma","doi":"10.1021/acs.jpca.4c05792","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c05792","url":null,"abstract":"<p><p>The spectroscopic and dynamic properties of methyl ferulate─a naturally occurring ultraviolet-protecting filter─and microsolvated methyl ferulate have been studied under molecular beam conditions using resonance-enhanced multiphoton ionization spectroscopy in combination with quantum chemical calculations. We demonstrate and rationalize how the phenyl substitution pattern affects the state ordering of the lower excited singlet state manifold and what the underlying reason is for the conformation-dependent Franck-Condon (FC) activity in the UV-excitation spectra. Studies on microsolvated methyl ferulate reveal potential coordination sites and the influence of such coordination on the spectroscopic properties. Our quantum chemical studies also enable us to obtain a quantitative understanding of the dominant excited-state decay routes of the photoexcited ππ* state involving a ∼3 ns intersystem crossing pathway to the triplet manifold─which is much slower than found for coumarates─and a relatively fast intersystem crossing back to the ground state (∼30 ns). We show that a common <i>T</i>₁/<i>S</i>₀ crossing can very well explain the observation that <i>T</i>₁ lifetimes are quasi-independent of the phenyl substitution pattern.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833163","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":"In Search of Entangled Singlet Pure Diradicals.","authors":"Georges Trinquier, Jean-Paul Malrieu","doi":"10.1021/acs.jpca.4c06971","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06971","url":null,"abstract":"<p><p>Recent work has documented conjugate polycyclic hydrocarbons presenting unusual properties: accepting full on-bond electron pairing, they could be considered as closed-shell architectures, but their ground-state wave function is actually a pure diradical singlet, free of any ionic component, in contrast to diradicaloids. These so-called <i>entangled</i> molecules also differ from disjoint diradicals, which do not accept on-bond electron pairing, in that their singly occupied molecular orbitals (SOMOs) are spatially entangled rather than disjoint. The present work first extends the study to a broad series of architectures exhibiting the same properties, namely: they present two degenerate SOMOs in the topological Hückel Hamiltonian, and their pure diradical wave functions lead to symmetry-keeping geometries. These solutions are always of lower energy than the closed-shell solutions that break symmetry and destroy aromaticity of some six-membered rings. A topological criterion ensuring that a given conjugate hydrocarbon will behave as an entangled pure diradical is then formulated. Next, a second set of molecules is proposed, still exhibiting two degenerate Hückel SOMOs, but with smaller contrast between the energies of open-shell and closed-shell solutions. Conservation of six-membered rings aromaticity appears as the driving factor ruling the stability of diradical solutions.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142845315","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":"General Spin-Restricted Open-Shell Configuration Interaction Approach: Application to Metal K-Edge X-ray Absorption Spectra of Ferro- and Antiferromagnetically Coupled Dimers.","authors":"Tiago Leyser da Costa Gouveia, Dimitrios Maganas, Frank Neese","doi":"10.1021/acs.jpca.4c05228","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c05228","url":null,"abstract":"<p><p>In this work, we present a generalized implementation of the previously developed restricted open-shell configuration interaction singles (ROCIS) family of methods. The new method allows us to treat high-spin (HS) ferro- as well as antiferromagnetically (AF) coupled systems while retaining the total spin as a good quantum number. To achieve this important and nontrivial goal, we employ the machinery of the iterative configuration expansion (ICE) method, which is able to tackle general configuration interaction (CI) problems on the basis of spin-adapted configuration state functions (CSFs). While ICE is designed to work in restricted orbital spaces, the new general-spin ROCIS (GS-ROCIS) method is designed to be applicable to larger molecules by employing a prototyping strategy. This new method can be applied to closed-shell, high-spin open-shell, as well as antiferromagnetic reference CSFs. In addition, GS-ROCIS can be combined with the pair natural orbital (PNO) machinery in the form of the PNO-GS-ROCIS method. With this extension, one can drastically reduce the required virtual space in the vicinity of the involved core orbitals, leading to computational savings of several orders of magnitude with negligible (<1%) loss in accuracy. To demonstrate the use of the new methodology, the metal K pre-edge X-ray absorption excitation problem of an antiferromagnetically coupled copper model dimer was investigated. By first analyzing a model copper dimer, it is shown that even for the minimum core excitation problem that involves the two antiferromagnetically coupled singly occupied orbitals and one virtual orbital, the resulting GS-ROCIS and broken-symmetry configuration interaction singles (BS-CIS) spectra may differ in terms of the number, energy position, and relative intensity of the computed bands. Furthermore, the methodology was validated to perform equally well in computing the K-edge spectra of antiferromagnetic nickel oxide dimers and mixed-valence cobalt oxide trimers. Collectively, the present development represents an important methodological advance in the application of theoretical X-ray spectroscopy.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833159","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":"Convergence Analysis and Predictions for Optimizing Reciprocal Grids: A First-Principles and Machine Learning Study.","authors":"Jinyoung Byun, Donggeon Lee, Euyheon Hwang, Sooran Kim, Ji-Sang Park","doi":"10.1021/acs.jpca.4c05782","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c05782","url":null,"abstract":"<p><p>When crystalline materials are investigated by performing first-principles density functional theory (DFT) calculations, the reciprocal grid should be fine enough to obtain the converged total energy and electronic structure. Herein, we performed a convergence test of the total energy for the density of reciprocal points to determine fine enough reciprocal grids for high-throughput calculations. Our results show that the nonlinearity of the band structures affects the convergence of the total energy, especially for materials with a finite band gap. We further investigate which physical properties make a finer reciprocal grid necessary based on machine learning (ML) analysis. Our developed models using DFT-based features and elemental properties-based features exhibit <i>R</i>² of 0.803 and 0.880, respectively. Our ML model quantitatively shows the importance of nonlinearity and band gaps in predicting errors in total energy calculations. Furthermore, our ML model using elemental features can be applied to estimate the appropriate reciprocal grid, facilitating high-throughput calculations.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833158","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":"Ro-Vibrational Spectrum of Vanadium Monoxide (VO) at 10 μm.","authors":"Eileen Döring, Luisa Blum, Alexander A Breier, Thomas F Giesen, Guido W Fuchs","doi":"10.1021/acs.jpca.4c05996","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c05996","url":null,"abstract":"<p><p>The high resolution ro-vibrational spectrum of the diatomic molecule vanadium oxide (VO) in the gas phase was measured around 1000 cm^-1. In total, 1529 ro-vibrational transitions were assigned, in a spectral range of 984-1036 cm^-1. For many transitions, the hyperfine structure resulting from the nuclear spin of ⁵¹V were resolved and the molecular parameters for the first (<i>v</i> = 1) and second (<i>v</i> = 2) excited vibrational state of VO were derived. The molecules were generated using a laser ablation source in which a vanadium rod was laser ablated and gaseous nitrous oxide (N₂O) was introduced, as an oxygen donor. Subsequent supersonic adiabatic expansion cooled the molecules. The spectrum of VO was measured with quantum cascade lasers where the laser beams were perpendicularly oriented to the supersonic jet.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833162","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 of Extensive Hydrogen Abstraction Reactions for 2-Hydroxyethylhydrazine (HEH).","authors":"Xin Bai, Ruining He, Shuyuan Liu, Qingbo Zhu, Zhandong Wang, Fang Wang, Yang Li","doi":"10.1021/acs.jpca.4c07404","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07404","url":null,"abstract":"<p><p>Energetic ionic liquids have a high potential to replace the traditional monopropellant hydrazine as a high-energy green propellant and can be widely used in aerospace technology. A high-energy ionic liquid─HEHN has also gained extensive attention from researchers. To explore the reaction mechanism of HEHN and establish a chemical kinetic model for high-energy ionic liquid propellants, 28 hydrogen abstraction reactions of HEH, which is the main decomposition product of HEHN, were investigated in this study. Seven abstractors were involved, including ^•H, ^•OH, NO₂, HO₂^•, ^•CH₃, CH₃O^•, and CH₃O₂^•. In the case of <i>ab initio</i> calculations, the M06-2<i>X</i>/6311++G(d,p) approach was utilized for geometry optimization, determination of vibrational frequencies, and dihedral scans. The CCSD/cc-pVXZ (X = T, Q) level of theory was used to calculate the single-point energies (SPEs). The rate coefficients of all 28 reactions and the thermochemical parameters of all involved species were determined. The results indicate that the rate of hydrogen abstraction at the -NH site is faster than that at other sites at relatively low temperatures. For all four abstraction sites, HEH + ^•H, ^•OH, and CH₃O^• have higher reaction rates than HEH + CH₃O₂^• and HO₂^•. In particular, NO₂ systems at the -NH and -NH₂ sites even begin to show higher reactivity than the ^•H, ^•OH, and CH₃O^• systems when the temperature is above ∼1100 K.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142833164","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}