The Journal of Physical Chemistry A最新文献

{"title":"Reactive Radical Etching of Quartz by Microwave Activated CH₄/H₂ Plasmas Promotes Gas Phase Nanoparticle Formation.","authors":"Michael N R Ashfold, Basile F E Curchod, Daniel Hollas, Jie Ma, Yuri A Mankelevich","doi":"10.1021/acs.jpca.4c05787","DOIUrl":"10.1021/acs.jpca.4c05787","url":null,"abstract":"<p><p>An attenuation of visible probe radiation identified in earlier absorption studies of microwave plasma-activated CH₄/H₂/Ar gas mixtures is shown to arise from nanoparticles in under-pumped regions on opposing sides of a reactor used for diamond chemical vapor deposition. The present modeling studies highlight (i) ejection of Si-containing species into the gas phase by reactive radical etching of the quartz window through which the microwave radiation enters the reactor, enabled by suitably high window temperatures (<i>T</i>_SiO2) and the synergistic action of near-window H atoms and C_<i>y</i>H_<i>x</i> radicals; (ii) subsequent processing of the ejected material, some of which are transported to and accumulate in stagnation regions in the entrance to the reactor side arms; and (iii) the importance of Si in facilitating homogeneous gas phase nucleation, clustering, and nanoparticle growth in these regions. The observed attenuation, its probe wavelength dependence, and its variations with changes in process conditions can all be rationalized by a combination of absorption and scattering contributions from Si/C/H containing nanoparticles with diameters <i>d</i> in the range of 50-100 nm. Possible implications for Si incorporation in CVD diamond samples are discussed.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"10884-10905"},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142805542","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":"The Investigation on the Reactivity and the Formation of Halogen Bond Complexes for the Reactions of α-Nucleophiles XO^- (X = F, *Cl, Br, I) and CH₃CH₂Cl.","authors":"Gang Fu, Wenqing Zhen, Hongyi Wang, Li Yang, Jiaxu Zhang","doi":"10.1021/acs.jpca.4c04190","DOIUrl":"10.1021/acs.jpca.4c04190","url":null,"abstract":"<p><p>Precise prediction of reactivity and accurately identifying the types of reaction complexes are prerequisites for delineating the microscopic mechanisms of ion-molecule reactions, which remain unclear for reactions involving α-nucleophilic reagents. Here, we investigate the potential energy surface of the multiatomic reactions XO^- (X = F, *Cl, Br, I) + CH₃CH₂Cl to elucidate the optimal descriptors for reaction reactivity and the origin of halogen bond/hydrogen bond compounds. Through analyzing the orbital composition and the relationship of energy barriers with the proton affinity and nucleophilic index, the local nucleophilic index is ultimately determined to be the optimal descriptor for predicting the reactivity of the reactions with α-nucleophilic reagents. Furthermore, it is found that the type of a reaction complex is closely related to the initial relative orientations of ions and molecules, the functional group substitutions, and the electrostatic potential extreme points of the halogen tops in the reactive substrates. In terms of the above factors, we can design suitable reaction substrates to generate intermolecular interactions with specific types, which is important in areas such as drug synthesis.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"10746-10757"},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142694884","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":"A Comparative Theoretical Study of the Atmospheric Chemistry of Dimethyl and Bis(trifluoromethyl) Sulfides.","authors":"Jiale He, Mi Zhang, Hua Hou, Baoshan Wang","doi":"10.1021/acs.jpca.4c07082","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c07082","url":null,"abstract":"<p><p>Dimethyl sulfide (CH₃SCH₃) is the largest natural source of atmospheric sulfur. Bis(trifluoromethyl) sulfides (CF₃SCF₃) are one of the perfluorinated thioethers with great interest as the new refrigerant fluid and dielectric replacement gas for the sake of environmental concern. In order to clarify the effect of fluorine substitution, degradation mechanisms and kinetics for the reactions of CH₃SCH₃ and CF₃SCF₃ with OH radicals in the atmosphere have been calculated comprehensively in a comparative manner using various high-level <i>ab initio</i> methods. It is revealed that the CH₃SCH₃ + OH reaction is predominated by addition/elimination and hydrogen abstraction mechanisms. A stable van der Waals complex exists via the long-range S···O interaction with a binding energy 9.1 kcal/mol, which decomposes straightforwardly by the S-C bond rupture. The collisional deactivation of the complex competes with two distinct hydrogen-abstraction paths. Theoretical rate coefficients are in good agreement with the available experimental data. In contrast, CF₃SCF₃ reacts with OH through the shallow wells (0.7 kcal/mol) to form the less stable tricoordinated S (III) covalent intermediates before the endothermic S-C bond fission. The room-temperature rate coefficient for the CF₃SCF₃ + OH reaction is 4 orders of magnitude lower than that for the CH₃SCH₃ + OH reaction. It is demonstrated that the atmospheric loss of CF₃SCF₃ has been retarded considerably with the lifetime around 300 years. The radiative efficiency is 0.463 W m^2- ppb^-1 and the global warming potential of CF₃SCF₃ is predicted to be approximately 14,000, indicative of a new super greenhouse gas. The present theoretical results will stimulate experimental studies of the dramatic impact on the reactivity of thioethers due to fluorination.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142851643","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 of Sulfates and Water to Monovalent Cations.","authors":"Mark J Stevens, Susan B Rempe","doi":"10.1021/acs.jpca.4c05454","DOIUrl":"10.1021/acs.jpca.4c05454","url":null,"abstract":"<p><p>The binding of the sulfate ligand group to monovalent cations in the presence of water is important for many systems. To understand the structure and energetics of sulfate complexes, we use density functional theory to study ethyl sulfate binding to the monovalent cations Li⁺, Na⁺, and K⁺, and to water. The free energies of binding and optimal structures are calculated for a range of the number of ethyl sulfates and waters. Without water, the most optimal structure for all the cations is bidentate binding by two ethyl sulfates, yielding a 4-fold coordination. With water, the lowest free energy structures also have two ethyl sulfates, but the coordination varies with cations. For complexes with water, the four oxygen atoms in the sulfate group enable multiple binding geometries for the cations and for hydrogen bonding with water. Many of these geometries differ in free energy by only a small amount (1-2 kcal/mol), meaning there will be multiple binding configurations in bulk solution. In comparison to the optimal structures for binding to the carboxylate group, there is more variation for binding to the sulfate group as a function of cation type and the number of waters. The polarization of the atoms is significant and varies among the sulfate oxygen atoms. The water oxygen charge is often larger than that of sulfate oxygen, which plays a role in the preference for monodentate ligand binding to cations in the presence of water.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"10785-10795"},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142789422","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":"Single-Sided Delocalized Polarization of the C₆₀ Cage and Reduced Infrared Intensities and Dipole Moment of H₂O@C₆₀.","authors":"Hajime Torii, Shumpei Sadai, Yoshifumi Hashikawa, Yasujiro Murata, Yuka Ikemoto","doi":"10.1021/acs.jpca.4c07072","DOIUrl":"10.1021/acs.jpca.4c07072","url":null,"abstract":"<p><p>The C₆₀ fullerene cage can encapsulate a small molecule like water and provides room to leave the encapsulated component rather isolated, but the true nature of the intracomplex interactions should be further elucidated for better understanding and utility of this series of complexes. Here, an analysis toward this goal is conducted for H₂O@C₆₀ by infrared spectral measurements and theoretical calculations. It is shown that the response of the π electrons of the C₆₀ cage upon encapsulating a water molecule is single-sided and delocalized in that the electron density is partially transferred from the -<i>z</i> side to the +<i>z</i> side of the cage (when the <i>z</i> axis is taken along the water dipole) but almost only inside the cage, explaining the significant reduction of the dipole moment and the infrared intensities. Those infrared intensities have a large temperature dependence in a way that the bands gain intensities upon lowering the temperature down to 10 K, possibly due to coupling with lattice phonons.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":"10867-10874"},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142790513","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":"Photoswitching Molecules Functionalized with Optical Cycling Centers Provide a Novel Platform for Studying Chemical Transformations in Ultracold Molecules.","authors":"Paweł Wójcik, Taras Khvorost, Guanming Lao, Guo-Zhu Zhu, Antonio Macias, Justin R Caram, Wesley C Campbell, Miguel A García-Garibay, Eric R Hudson, Anastassia N Alexandrova, Anna I Krylov","doi":"10.1021/acs.jpca.4c06320","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06320","url":null,"abstract":"<p><p>A novel molecular structure that bridges the fields of molecular optical cycling and molecular photoswitching is presented. It is based on a photoswitching molecule azobenzene functionalized with one and two CaO- groups, which can act as optical cycling centers (OCCs). This paper characterizes the electronic structure of the resulting model systems, focusing on three questions: (1) how the electronic states of the photoswitch are impacted by a functionalization with an OCC; (2) how the states of the OCC are impacted by the scaffold of the photoswitch; and (3) whether the OCC can serve as a spectroscopic probe of isomerization. The experimental feasibility of the proposed design and the advantages that organic synthesis can offer in the further functionalization of this molecular scaffold are also discussed. This work brings into the field of molecular optical cycling a new dimension of chemical complexity intrinsic to only polyatomic molecules.</p>","PeriodicalId":59,"journal":{"name":"The Journal of Physical Chemistry A","volume":" ","pages":""},"PeriodicalIF":2.7,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142862538","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":"The Noncovalent Interaction in Dinuclear Bridged Gold(I) Complexes: A Theoretical Study.","authors":"Dina Lara, Néstor Gutiérrez-Sánchez, Sebastián Miranda-Rojas, Fernando Mendizabal","doi":"10.1021/acs.jpca.4c06026","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c06026","url":null,"abstract":"<p><p>We present a study of the cooperative nature of the forces dominating the interaction between gold atoms and aryl-aryl stacking. For this purpose, we modeled a series of complexes of the type dpm(AuR)₂ (dpm= bis(phoshino)methane; R = -C₆H₅, -C₆F₅, -C₆Cl₅, and -Cl). The models were calculated at the MP2, CCSD(T), and DFT-D3(BJ) (PBE and TPSS) levels of theory. The results show Au-Au and aryl-aryl stacking distances associated with noncovalent interactions. Also, the Wiberg indices, NBO, NCI, and QTAIM analyses exposed a low-density character between the gold atoms and aryl-aryl stacking, revealing that this contribution explains the stability of the complexes via dispersive interactions. Finally, the absorption spectra obtained are comparable with the experimental ones, and the orbitals obtained demonstrate that after the transitions, the orbitals are delocalized between the gold atoms and the vertex atoms of the molecules.</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":"142845317","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":"Revisiting the Optical Spectrum of the Plutonyl Ion (PuO₂)²⁺ in 1 M HClO₄.","authors":"Norman M Edelstein","doi":"10.1021/acs.jpca.4c05837","DOIUrl":"https://doi.org/10.1021/acs.jpca.4c05837","url":null,"abstract":"<p><p>The analysis of the solution absorption spectrum of the plutonyl ion in an aqueous environment was given by Eisenstein and Pryce (E&P) in 1968. In 2011 a new spectrum was published of the (PuO₂)²⁺ ion in 1 M HClO₄. We have been provided with the original data of this spectrum and have found in the data a previously unreported low-lying transition at 7385 cm^-1 which we have assigned as a magnetic dipole transition. We have fit most of the near-infrared and optical transitions with Gaussian fits and tabulated a new energy level list up to 22,000 cm^-1 which mostly agrees with the data of E&P. We assumed a crystal field of D_∞h (only axial symmetry) and utilized the intensity calculations published for the isoelectronic (NpO₂)¹⁺ ion using a complete basis set for the 5f² problem including the Coulombic, spin-orbit as well as the crystal field Hamiltonian. Our results differ substantially from those of E&P. Subsequently, we used a truncated Hamiltonian to try to establish the effects of assuming the σ antibonding orbitals are at such high energies that we can ignore their contributions to the lower lying φ and δ orbitals.</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":"142851656","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":"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}