The Journal of Physical Chemistry B最新文献

{"title":"Significant Effects of Excitonic Coupling and Charge Transfer on the Circular Dichroism Spectrum of Photosynthetic Light-Harvesting I Complex.","authors":"Rio Tsuji, Kazuhiro J Fujimoto, Naho Hiwatashi, Zheng-Yu Wang-Otomo, Takeshi Yanai","doi":"10.1021/acs.jpcb.5c02145","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c02145","url":null,"abstract":"<p><p>Spectral properties of light-harvesting (LH) complexes are key to understanding excitation-energy transfer in photosynthesis. This study examines the physicochemical factors that shape the circular dichroism (CD) spectrum of LH1 in <i>Rhodospirillum rubrum</i>. Calculations using four computational models reveal that intermolecular electronic interactions, particularly excitonic coupling, primarily determine the LH1 CD spectrum shape, while charge transfer effects contribute significantly to the redshift of the peaks. Another finding is that the LH1-specific spectrum shape arises from excitonic coupling extending over 12 bacteriochlorophyll (BChl) <i>a</i> molecules. Further computational analysis additionally identified an anticlockwise rotation of the transition dipole moments of the BChl <i>a</i> assembly as a contributing factor. Our results demonstrate how slight variations in intermolecular orientation influence CD spectrum shape, offering insight into the mechanisms governing the optical properties of light-harvesting antennas. Our computational approach advances the systematic study of CD spectrum shapes associated with chromophore aggregation.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300703","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":"Self-Assembly of Pseudo Isocyanine Chloride in the Presence of Attractive Polyethylene Glycol Crowders.","authors":"Leon Koch, Satyendra Rajput, Antonio Richter, Benedikt König, Divya Nayar, Simon Ebbinghaus, Klaus Huber","doi":"10.1021/acs.jpcb.4c06843","DOIUrl":"https://doi.org/10.1021/acs.jpcb.4c06843","url":null,"abstract":"<p><p>The present work analyzes the impact of a synthetic model crowder on the self-assembly of a probe in aqueous solution. Pseudo isocyanine chloride (PIC) serves as a probe exhibiting self-assembly to fiber-like aggregates and thus representing a widespread phenomenon in biological cells. Ethylene glycol (EG) or polyethylene glycol (PEG) is used as a model crowder. The specific feature of this type of crowder is an attractive interaction to the PIC cation, thereby retarding the self-assembly of PIC instead of promoting it. First, the self-assembly of PIC is analyzed in the presence of EG. The results are interpreted by means of preferential adsorption of EG on PIC cations and by means of a model process in which nucleation initiates chain growth via monomer addition. Supplemented by molecular dynamics simulations on PIC in aqueous solutions of EG, these experiments provide a microscopic understanding of the nature of the interaction between PIC and EG and their effect on the PIC self-assembly. Experiments are then extended to several PEG samples, differing in their degree of polymerization. The inhibiting effect of PEG crowders is found to be quantified by the number density of the monomeric EG units in the PEG chains rather than the number density of PEG chains, discarding significant volume exclusion effects of PEG-based crowders on the PIC self-assembly. The work thus unravels as a particular feature the impact of attractive crowder-probe interactions on the self-assembly of a probe. Results are not only highly relevant for biological systems but also support future developments in sensor technology based on the insight gained with this responsive synthetic model system.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300702","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":"Mobile-Phase Contributions to Analyte Retention and Selectivity in Reversed-Phase Liquid Chromatography: 2. Solute-Specific Effects.","authors":"Andreas Steinhoff, Alexandra Höltzel, Ulrich Tallarek","doi":"10.1021/acs.jpcb.5c01697","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c01697","url":null,"abstract":"<p><p>Analyte retention in reversed-phase liquid chromatography decreases with increasing solute polarity of a compound, whereby the parameters of the water-organic solvent (W-OS) mobile phase can influence the retention order of the compounds (selectivity). Through molecular dynamics simulations in a slit-pore model of a silica-based, endcapped, C₁₈ stationary phase equilibrated with W-methanol and W-acetonitrile mobile phases, we investigate how the system discriminates between small, neutral compounds with low to moderate solute polarity at the molecular level. The experimental retention behavior of the analyte ensemble was recovered by the stationary phase-averaged number of bonded-phase contacts per analyte molecule, which depends on the number of hydrophobic structural elements in a compound and its average penetration depth into the bonded-phase chains. Evasion of W contacts by the hydrophobic structural elements pushes an analyte molecule deeper into the bonded-phase chains, but only as far as allowed by its hydrogen-bond requirements, which limit the analyte density in the solvated stationary phase to locations with sufficient W density. Selectivity effects arise when mobile phase-induced changes in stationary-phase solvation alter the density limitations of a compound relative to another. Differential analyte retention results therefore from the solute-specific response to the mobile phase-controlled W density distribution in the system.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300701","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 Importance of Hydrogen Bonded Networks in the Dynamic Heterogeneity of Deep Eutectic Solvents.","authors":"Allison Stettler, Gary A Baker, G J Blanchard","doi":"10.1021/acs.jpcb.5c02468","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c02468","url":null,"abstract":"<p><p>We have examined the composition-dependent rotational diffusion dynamics of the chromophores perylene (neutral), oxazine 725 (cationic) and disodium fluorescein (anionic) in a series of choline chloride/1,3-propanediol (ChCl/PD) deep eutectic solvents (DESs). We find that the rotational diffusion dynamics of all chromophores do not correlate with the bulk viscosities of any of these ChCl/PD DES compositions, consistent with dynamic heterogeneity in all cases. Comparison with other DES systems─choline chloride/ethylene glycol (ChCl/EG) and choline chloride/glycerol (ChCl/Gly)─enables evaluation of the influence of hydrogen bond donor (HBD) structure and hydroxyl group density. This comparison highlights the critical role of hydrogen-bonded networks in these DESs and underscores the pivotal function of ChCl in disrupting these networks at ca. 15 mol % ChCl across all three DES systems. Taken collectively, these data point to the constituent structural factors that mediate the properties of DESs on local and bulk scales.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300704","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":"Influence of Internal Interfaces on the Structure and Dynamics of IL-Based Electrolytes Confined in a Metal-Organic Framework.","authors":"Janis Hessling, Leonard Dick, Sophia Keil, Vahideh Alizadeh, Michael Ryan Hansen, Barbara Kirchner, Monika Schönhoff","doi":"10.1021/acs.jpcb.5c01702","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c01702","url":null,"abstract":"<p><p>Hybrid solid-state electrolytes, which combine ionic liquids with metal-organic frameworks, offer a promising approach to enhancing the safety and energy density of next-generation batteries. A thorough understanding of the interplay between the solid and liquid phases in hybrid solid-state electrolytes is crucial for optimizing their performance as battery electrolytes. This study investigates how interactions between different ionic liquid-based electrolytes and the metal-organic framework ZIF-8 influence the coordination and dynamics of Li⁺ in confinement. To this end, we examine five different ionic liquids, varying the chemical nature of the cation. Raman spectroscopy, supported by 2D solid-state NMR and simulations, are used to elucidate Li⁺ coordination and ion-wall interactions. The impact of these interactions on local Li⁺ dynamics and charge transport in the ionic liquid-ZIF-8 hybrid system is investigated using ⁷Li spin relaxation, impedance spectroscopy, and simulations. The results reveal a competitive interaction between Li⁺ and the ionic liquid cation with the ZIF-8 framework, which can be fine-tuned by modifying the molecular structure of the ionic liquid cation. As a consequence, local Li⁺ dynamics is enhanced, depending on the ionic liquid cation. The beneficial interactions in the confined system can even make Li⁺ the fastest diffusing species, in contrast to bulk electrolyte, where Li⁺ transport is limited by strong Li-anion clusters. Thus, blocking Li⁺-framework interactions through other competitive interactions might be an effective strategy to enhance Li⁺ dynamics and increase Li conductivity in a hybrid solid-state electrolyte. Although confinement within the ZIF-8 model system leads to an overall decrease in conductivity, this study provides valuable insights into the design of hybrid electrolytes for next-generation battery applications.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144309307","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":"Direct Measurement of the Effect of Cholesterol and 7-Dehydrocholesterol on Membrane Dipole Electric Field in Single and Mixed Sterol Vesicles Using Vibrational Stark Effect Spectroscopy.","authors":"Sydney C Povilaitis, Jessica A Hector, Morgan E Mantsch, Lauren J Webb","doi":"10.1021/acs.jpcb.5c00279","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c00279","url":null,"abstract":"<p><p>Cholesterol is an important contributor to the properties, structure, and function of biological membranes. An immediate biosynthetic precursor to cholesterol, 7-dehydrocholesterol (7DHC), differs only in a single double bond, yet defects in the conversion of 7DHC to cholesterol result in metabolic disorders. The membrane dipole field, <i>F⃗</i>_d, is the greatest contributor to the total membrane electric field and arises from the alignment of interfacial lipids and water molecules. We have previously shown, using vibrational stark effect (VSE) spectroscopy, that the magnitude of membrane dipole field decreases with increasing cholesterol content and that sterol structure can differentially affect <i>F⃗</i>_d. Here, we employ VSE spectroscopy to directly measure <i>F⃗</i>_d in small unilamellar vesicles (SUVs) composed of DMPC and 0-40% cholesterol or 7DHC. Our results show that cholesterol and 7DHC influence <i>F⃗</i>_d in a similar way, reducing the magnitude of <i>F⃗</i>_d with increasing sterol content in a trimodal manner corresponding to phase transitions in DMPC/sterol bilayers. To probe <i>F⃗</i>_d in membranes that better model diseased states, VSE measurements were performed on SUVs with 40% total sterol, but mixed compositions of cholesterol and 7DHC. <i>F⃗</i>_d was bimodal in these systems, reflecting a 7DHC-like field at 10% cholesterol/30% 7DHC but a cholesterol-like content at 15% cholesterol (25% 7DHC) and above. We propose possible sources of these trimodal and bimodal effects and discuss the implications on our understanding of membrane electrostatics and cholesterol-related metabolic disorders.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144300700","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":"Low-Temperature Structural Study of Smectic C_A* Glass by X-ray Diffraction.","authors":"Aleksandra Deptuch, Marcin Kozieł, Marcin Piwowarczyk, Magdalena Urbańska, Ewa Juszyńska-Gałązka","doi":"10.1021/acs.jpcb.5c03603","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c03603","url":null,"abstract":"<p><p>The liquid crystalline compound, forming the glass of the smectic C_A* phase, is investigated by X-ray diffraction in the 18-298 K range. The characteristic distances within the smectic C_A* phase are determined, and the specific volume is estimated. The electron density profile along the smectic layer normal is inferred and compared with the results of the density functional theory calculations. Observations of the selective reflection of the visible light investigate the helical ordering within the smectic C_A* glass. The results indicate slow change with temperature of the smectic layer spacing, intermolecular distances, and electron density distribution below the glass transition temperature. The change in the temperature dependence of the specific volume is well below the glass transition temperature. Meanwhile, the relative range of the short-range order within the smectic layers and the helix pitch are rather constant in the glassy state.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144292983","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":"Solvation Free Energies of Ion Dissociations in Dichloromethane: En Route to Accurate Computations.","authors":"Adélaïde Savoy, Eno Paenurk, Robert Pollice, Philippe H Hünenberger, Peter Chen","doi":"10.1021/acs.jpcb.5c01446","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c01446","url":null,"abstract":"<p><p>Calculating accurate free energies for solution-phase reactions is notoriously difficult. In our previous joint experimental and computational studies, we observed a striking failure of quantum mechanical calculations with popular implicit solvent models to even qualitatively reproduce the experimental trends of dissociation free energies of numerous proton-bound pyridine dimers in organic solvents [Pollice, R. . <i>J. Am. Chem. Soc.</i> 2017, 139(37), 13126-13140]; [Pollice, R. . <i>Angew. Chem., Int. Ed.</i> 2019, 58(40), 14281-14288]. In this article, we expand the computational study of the dissociation of proton-bound pyridine dimers in the gas phase and in dichloromethane (DCM). In an effort to determine the prerequisites for reproducing the experimental trends and magnitudes of the dissociation free energies (Δ<i>G</i>_diss) in solvent, we investigated the impact of accounting for the ensemble free energy, umbrella sampling, thermodynamic integration, and explicit solvation using semiempirical quantum mechanics and molecular mechanics. We estimated the effect of conformational free energy contributions with semiempirical quantum mechanics (SE). Molecular dynamics (MD) with explicit solvation and classical molecular mechanics (MM) was used as a method to treat not only the solute but also the solvent configurational entropy. We found that explicit solvation with MM is indeed capable of reproducing Δ<i>G</i>_diss in DCM for our test system within an acceptable error margin. We analyze and discuss the results and limitations of our approach for calculating the solvation free energy.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281646","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":"Exciton Coupling and Charge Transfer Dynamics in Zn(II) Complexes of π-Extended Dipyrrins.","authors":"Dabin Kim, Luca Ravotto, April Bialas, Thomas Troxler, Zhongping Ou, Karl M Kadish, Andrei V Cheprakov, Frank C Spano, Sergei A Vinogradov, Jessica M Anna","doi":"10.1021/acs.jpcb.5c03312","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c03312","url":null,"abstract":"<p><p>Dipyrrins form a group of versatile chromophores, which find use as laser dyes as well as in light harvesting and bioimaging applications. The mode of the central ion coordination and the ensuing molecular geometry play a key role in the photophysics of dipyrrins, whereby some complexes are brightly fluorescent and some completely lack emissivity. However, the relationship between the structure and excitation dynamics in dipyrrins is still poorly understood. Here, we used a range of spectroscopic methods to investigate the photophysics of Zn(II) complexes of <i>meso</i>-Ar-2,2'-di-<i>tert</i>-butoxycarbonyl-dibenzodipyrrins (BDP; Ar = 4-MeO₂C-C₆H₄). In particular, two-dimensional electronic spectroscopy (2DES) was used to characterize the initial excited states in a homoleptic <i>bis</i>-dipyrrinate Zn(BDP)₂, in which two dipyrrin ligands are oriented in a nonorthogonal geometry. From the position of the peaks in the 2DES spectra and spectral modeling, the initial excited states of Zn(BDP)₂ were assigned to excitonic states. The low oscillator strength, associated with excitation to the lower excitonic state, is responsible in part for the weak emissivity of Zn(BDP)₂, contrasting the bright fluorescence of <i>mono</i>-dippyrinate Zn(BDP)X. Femtosecond (fs-), nanosecond (ns-) transient absorption (TA), and time-resolved fluorescence spectroscopies were used to monitor the solvent-dependent evolution of the excitonic states, which appear to evolve into an intermediate state possibly with charge transfer character. Taken together, our findings reveal a significant impact of both structural and environmental factors on the photophysics of dipyrrins and present the first example of the application of 2DES to investigate excitonic states in a system where the interacting chromophores are held together via coordination of an optically neutral metal ion. On a broader scale, we demonstrate that nonorthogonal <i>bis</i>-dipyrrin complexes constitute a versatile model for studying exciton coupling and associated energy and charge dynamics.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144289356","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":"Thermally Invertible Helical PEDOTs Synthesized by Asymmetric Electrochemical Polymerization in Temperature-Responsive Chiral Liquid Crystals.","authors":"Yoshinori Okada, Keita Horie, Kazuo Akagi","doi":"10.1021/acs.jpcb.5c02914","DOIUrl":"https://doi.org/10.1021/acs.jpcb.5c02914","url":null,"abstract":"<p><p>A thermal stimulus-responsive chiral nematic liquid crystal (N*-LC) is prepared by adding a chiral dopant with a thermally switchable helical sense into a host nematic liquid crystal. The helical sense of the N*-LC is reversibly controlled with a temperature difference of just 20 °C. Helical poly(3,4-ethylenedioxythiophene)s (H-PEDOTs) are synthesized through the asymmetric electrochemical polymerization of <i>ter</i>-ethylenedioxythiophene (EDOT) in N*-LCs containing an electrolyte. The helical senses of the H-PEDOTs are rigorously controlled by modulating the polymerization temperature. Changes in the chiroptical and electrochemical properties of H-PEDOTs upon electrochemical doping and dedoping were investigated. The circular dichroism (CD) spectra measured from the visible to near-infrared regions indicate that the helically π-stacked structure formed in neutral H-PEDOT is preserved even in oxidized H-PEDOT after electrochemical doping. This is the first example revealing that a helically π-stacked structure exists in the polaron and bipolaron states of conjugated polymers. The relationships between the helical sense of the N*-LC and those of the helically π-stacked structure, screwed fibril bundles and spiral morphology of the H-PEDOT were elucidated using a newly proposed mechanism for electrochemical polymerization in the N*-LC.</p>","PeriodicalId":60,"journal":{"name":"The Journal of Physical Chemistry B","volume":" ","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144281647","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}