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Jurado Romero A, Calero C, Sibert EL, Rey R. High energy vibrational excitations of nitromethane in liquid water. J Chem Phys 2023; 158:2890474. [PMID: 37184013 DOI: 10.1063/5.0147459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 04/28/2023] [Indexed: 05/16/2023] Open
Abstract
The pathways and timescales of vibrational energy flow in nitromethane are investigated in both gas and condensed phases using classical molecular mechanics, with a particular focus on relaxation in liquid water. We monitor the flow of excess energy deposited in vibrational modes of nitromethane into the surrounding solvent. A marked energy flux anisotropy is found when nitromethane is immersed in liquid water, with a preferential flow to those water molecules in contact to the nitro group. The factors that permit such anisotropic energy relaxation are discussed, along with the potential implications on the molecule's non-equilibrium dynamics. In addition, the energy flux analysis allows us to identify the solvent motions responsible for the uptake of solute energy, confirming the crucial role of water librations. Finally, we also show that no anisotropic vibrational energy relaxation occurs when nitromethane is surrounded by argon gas.
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Affiliation(s)
- Arnau Jurado Romero
- Departament de Física, Universitat Politècnica de Catalunya, Barcelona 08034, Spain
| | - Carles Calero
- Departament de Física de la Matèria Condensada and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Edwin L Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Rossend Rey
- Departament de Física, Universitat Politècnica de Catalunya, Barcelona 08034, Spain
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2
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Neupane P, Katiyar A, Bartels DM, Thompson WH. Investigation of the Failure of Marcus Theory for Hydrated Electron Reactions. J Phys Chem Lett 2022; 13:8971-8977. [PMID: 36136966 DOI: 10.1021/acs.jpclett.2c02168] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Reactions of the hydrated electron with a wide variety of substrates have been found to exhibit unusually similar activation energies in a manner incompatible with Marcus electron transfer theory. Given the fundamental linear response assumption of Marcus theory, one possible explanation for this apparent failure is that the underlying free energy surfaces governing the reactions are not harmonic; i.e., hydrated electron structural fluctuations exhibit non-Gaussian behavior. In this work, we test this hypothesis by using simulations to calculate the hydrated electron vertical detachment energy distribution. We consider both cavity and noncavity models for the hydrated electron, between which the actual hydrated electron behavior is expected to lie. Our results identify a possible origin for non-Gaussian behavior of the hydrated electron but show that it is not of sufficient magnitude to explain the failure of Marcus theory to describe its reactions. Thus, other explanations must be sought.
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Affiliation(s)
- Pauf Neupane
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - Ankita Katiyar
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
| | - David M Bartels
- Notre Dame Radiation Laboratory & Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Ward H Thompson
- Department of Chemistry, University of Kansas, Lawrence, Kansas 66045, United States
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3
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Vong A, Schwartz BJ. Bond-Breaking Reactions Encounter Distinct Solvent Environments Causing Breakdown of Linear Response. J Phys Chem Lett 2022; 13:6783-6791. [PMID: 35856802 DOI: 10.1021/acs.jpclett.2c01656] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Solvent effects are important for understanding solution-phase chemical reactions. Surprisingly, very few studies have explored how solvent dynamics change during the course of a reaction with solutes that encounter a wide range of configurations. Here, we use quantum simulation methods to explore the solvent dynamics during a solution-phase bond-breaking reaction: the photodissociation of Na2+ in liquid Ar. We find that the solute experiences a small number of distinct solvent environments that change in a discrete fashion as the bond lengthens. In characterizing the solvent environments, we show also that linear response fails by all measures, even when nonstationarity of solvent dynamics is considered. This observation of distinct solvent response environments with a solvent that can undergo only translational motions highlights the complexity of solute-solvent interactions, but that there are only a few environments gives hope to the idea that solvation dynamics can be understood for solution-phase reactions that explore a wide configuration space.
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Affiliation(s)
- Andy Vong
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
| | - Benjamin J Schwartz
- Department of Chemistry & Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States
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Hodge SR, Berg MA. Nonlinear measurements of kinetics and generalized dynamical modes. I. Extracting the one-dimensional Green's function from a time series. J Chem Phys 2021; 155:024122. [PMID: 34266246 DOI: 10.1063/5.0053422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Often, a single correlation function is used to measure the kinetics of a complex system. In contrast, a large set of k-vector modes and their correlation functions are commonly defined for motion in free space. This set can be transformed to the van Hove correlation function, which is the Green's function for molecular diffusion. Here, these ideas are generalized to other observables. A set of correlation functions of nonlinear functions of an observable is used to extract the corresponding Green's function. Although this paper focuses on nonlinear correlation functions of an equilibrium time series, the results are directly connected to other types of nonlinear kinetics, including perturbation-response experiments with strong fields. Generalized modes are defined as the orthogonal polynomials associated with the equilibrium distribution. A matrix of mode-correlation functions can be transformed to the complete, single-time-interval (1D) Green's function. Diagonalizing this matrix finds the eigendecays. To understand the advantages and limitation of this approach, Green's functions are calculated for a number of models of complex dynamics within a Gaussian probability distribution. Examples of non-diffusive motion, rate heterogeneity, and range heterogeneity are examined. General arguments are made that a full set of nonlinear 1D measurements is necessary to extract all the information available in a time series. However, when a process is neither dynamically Gaussian nor Markovian, they are not sufficient. In those cases, additional multidimensional measurements are needed.
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Affiliation(s)
- Stuart R Hodge
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Mark A Berg
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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Hodge SR, Corcelli SA, Berg MA. Nonlinear measurements of kinetics and generalized dynamical modes. II. Application to a simulation of solvation dynamics in an ionic liquid. J Chem Phys 2021; 155:024123. [PMID: 34266263 DOI: 10.1063/5.0053424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Solvation dynamics in ionic liquids show features that are often associated with supercooled liquids, including "stretched" nonexponential relaxation. To better understand the mechanism behind the stretching, the nonlinear mode-correlation methods proposed in Paper I [S. R. Hodge and M. A. Berg, J. Chem. Phys. 155, 024122 (2021)] are applied to a simulation of a prototypical ionic liquid. A full Green's function is recovered. In addition, specific tests for non-Gaussian dynamics are made. No deviations from Gaussian dynamics are found. This finding is incompatible with rate heterogeneity as a cause of the nonexponential relaxation and appears to be in conflict with an earlier multidimensional analysis of the same data. Although this conflict is not resolved here, this work does demonstrate the practicality of mode-correlation analysis in the face of finite datasets and calculations.
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Affiliation(s)
- Stuart R Hodge
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
| | - Steven A Corcelli
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - Mark A Berg
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA
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Rey R, Hynes JT. Solvation Dynamics in Water. 4. On the Initial Regime of Solvation Relaxation. J Phys Chem B 2020; 124:7668-7681. [PMID: 32790403 DOI: 10.1021/acs.jpcb.0c05706] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It is shown, by means of numerical and analytic work, that initial molecular momenta play little significant role in the initial fast solvation relaxation that follows electronic excitation of, and charge creation for, a standard model system of a solute in water. Instead, the nonequilibrium dynamics are predominantly described by noninertial "steering" by the torques directly generated by the newly created charge distribution. It is this process that largely overcomes inertia and drives the relaxation dynamics on a time scale of a few tens of femtoseconds in the key initial regime of the dynamics. These results are discussed in the context of commonly employed descriptions such as inertial, Gaussian, and underdamped dynamical behavior.
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Affiliation(s)
- Rossend Rey
- Departament de Fı́sica, Universitat Politècnica de Catalunya, Campus Nord B4-B5, Barcelona 08034, Spain
| | - James T Hynes
- PASTEUR, Department of Chemistry, École Normale Supérieure, PSL University, Sorbonne Université, CNRS, 75005 Paris, France.,Department of Chemistry, University of Colorado, Boulder, Colorado 80309, United States
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Wang X, Guo J, Li T, Wei Z. To unravel the connection between the non-equilibrium and equilibrium solvation dynamics of tryptophan: success and failure of the linear response theory of fluorescence Stokes shift. RSC Adv 2020; 10:18348-18354. [PMID: 35517244 PMCID: PMC9053704 DOI: 10.1039/d0ra01227k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Accepted: 04/15/2020] [Indexed: 11/21/2022] Open
Abstract
The connections between the non-equilibrium solvation dynamics upon optical transitions and the system's equilibrium fluctuations are explored in aqueous liquid. Linear response theory correlates time-dependent fluorescence with the equilibrium time correlation functions. In the previous work [T. Li, J. Chem. Theory Comput., 2017, 13, 1867], Stokes shift was explicitly decomposed into the contributions of various order time correlation functions on the excited state surface. Gaussian fluctuations of the solute-solvent interactions validate linear response theory. Correspondingly, the deviation of the Gaussian statistics causes the inefficiency of linear response evaluation. The above mechanism is thoroughly tested in this study. By employing molecular simulations, multiple non-equilibrium processes, not necessarily initiated from the ground state equilibrium minimum, were examined for tryptophan. Both the success and failure of linear response theory are found for this simple system and the mechanism is analyzed. These observations, assisted by the width dynamics, the initial state linear response approach, and the variation of the solvation structures, integrally verify the virtue of the excited state Gaussian statistics on the dynamics of Stokes shift.
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Affiliation(s)
- Xiaofang Wang
- School of Physics and Optoelectronic Engineering, Xidian University Xi'an 710071 People's Republic of China
| | - Jirui Guo
- School of Physics and Optoelectronic Engineering, Xidian University Xi'an 710071 People's Republic of China
| | - Tanping Li
- School of Physics and Optoelectronic Engineering, Xidian University Xi'an 710071 People's Republic of China
| | - Zhiyi Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences Beijing 100190 China
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Guo J, Wang X, Li T, Wei Z. Linear Response Theory for Decomposition Energies of Stokes Shift in Proteins. J Phys Chem B 2020; 124:3540-3547. [PMID: 32212659 DOI: 10.1021/acs.jpcb.9b11519] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In aqueous solution, fluorescence Stokes shift experiments monitor the relaxation of the solute-solvent interactions upon photon excitation of the solute chromophore. Linear response (LR) theory expects the identical dynamics between the Stokes shift and the system's spontaneous fluctuations. Whether this identity guarantees similar dynamics between the nonequilibrated and equilibrium processes for the decomposition energy of the Stokes shift is the main focus of this study. In our previous work [Li, T. J. Chem. Theory Comput. 2017, 13, 1867-1873], Stokes shift is properly correlated with various order time-correlation functions. As a continuation, its decomposition energy from the subsystem is further represented as the full summation of all of the cross-time correlation functions between the decomposition energy and the total solute-solvent interactions. Gaussian statistics of the total solute-solvent interactions ensure the same decay rates among the odd orders not only for the time-correlation functions but also for the cross-time correlation functions, validating the LR of the Stokes shift and the decompositions, respectively. The above mechanism is verified by molecular dynamics simulations in the protein Staphylococcus nuclease and is robust even as the decomposed energy associated with an individual residue exhibits typical non-Gaussian properties. Further examinations reveal the consistent molecular motions for a specific residue over the nonequilibrium and equilibrium processes, which are responsible for the nonequilibrium dynamics of the associated decomposed energy. Our results show the appropriateness of LR on finer molecular scales.
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Affiliation(s)
- Jirui Guo
- School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, People's Republic of China
| | - Xiaofang Wang
- School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, People's Republic of China
| | - Tanping Li
- School of Physics and Optoelectronic Engineering, Xidian University, Xi'an 710071, People's Republic of China
| | - Zhiyi Wei
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Calero C, Sibert Iii EL, Rey R. Self-thermophoresis at the nanoscale using light induced solvation dynamics. NANOSCALE 2020; 12:7557-7562. [PMID: 32227019 DOI: 10.1039/d0nr01169j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Downsizing microswimmers to the nanoscale, and using light as an externally controlled fuel, are two important goals within the field of active matter. Here we demonstrate using all-atom molecular dynamics simulations that solvation relaxation, the solvent dynamics induced after visible light electronic excitation of a fluorophore, can be used to propel nanoparticles immersed in polar solvents. We show that fullerenes functionalized with fluorophore molecules in liquid water exhibit substantial enhanced mobility under external excitation, with a propulsion speed proportional to the power dissipated into the system. We show that the propulsion mechanism is quantitatively consistent with a molecular scale instance of self-thermophoresis. Strategies to direct the motion of functionalized fullerenes in a given direction using confined environments are also discussed.
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Affiliation(s)
- Carles Calero
- Departament de Física de la Matèria Condensada and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Edwin L Sibert Iii
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Rossend Rey
- Departament de Física, Universitat Politècnica de Catalunya, Barcelona 08034, Spain.
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Honegger P, Heid E, Schröder C, Steinhauser O. Dielectric spectroscopy and time dependent Stokes shift: two faces of the same coin? Phys Chem Chem Phys 2020; 22:18388-18399. [DOI: 10.1039/d0cp02840a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Different types of spectroscopy capture different aspects of dynamics and different ranges of intermolecular contributions.
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Affiliation(s)
- Philipp Honegger
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- 1090 Vienna
- Austria
| | - Esther Heid
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- 1090 Vienna
- Austria
| | - Christian Schröder
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- 1090 Vienna
- Austria
| | - Othmar Steinhauser
- University of Vienna
- Faculty of Chemistry
- Department of Computational Biological Chemistry
- 1090 Vienna
- Austria
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11
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Li T, Wang X. Theoretical Insights on Nonlinear Response Theory of Fluorescence Spectroscopy in Liquids. J Chem Theory Comput 2019; 15:471-476. [PMID: 30550279 DOI: 10.1021/acs.jctc.8b00538] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Correlations between the nonequilibrium solvation dynamics upon the photon excitation of the chromophore and a system's equilibrium fluctuations are deeply studied. As the linear response of the solvent has been linked with Gaussian statistics of the energy fluctuations in the literature, we specifically explore the cases beyond the regime of the linear response theory due to deviation from Gaussian fluctuations. As a continuation of our previous work, an analytical formalism is presented to project the energy shift with various order moments, where the non-Gaussian statistics arise from the overlap of the energy basins on the perturbed potential energy surface. It is shown that the nonequilibrium dynamics still correlate with the spontaneous regressions at equilibrium and are controlled by the decay rates of those higher order components with the prevailing contributions to the energy shift. Molecular dynamics simulations were performed in the protein Staphylococcus nuclease, in which even the dynamics of the high order moments are available. The results further verify the above relationship. Our scheme is used to evaluate Stokes shift using the information on non-Gaussian statistics at equilibrium, thus presenting a broad picture on the correlation between the nonequilibrium process and equilibrium properties in liquids.
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Affiliation(s)
- Tanping Li
- School of Physics and Optoelectronic Engineering , Xidian University , Xi'an , 710071 , People's Republic of China
| | - Xiaofang Wang
- School of Physics and Optoelectronic Engineering , Xidian University , Xi'an , 710071 , People's Republic of China
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Heid E, Schröder C. Solvation dynamics in polar solvents and imidazolium ionic liquids: failure of linear response approximations. Phys Chem Chem Phys 2018; 20:5246-5255. [PMID: 29400383 PMCID: PMC5815284 DOI: 10.1039/c7cp07052g] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/19/2018] [Indexed: 12/18/2022]
Abstract
This study presents the large scale computer simulations of two common fluorophores, N-methyl-6-oxyquinolinium betaine and coumarin 153, in five polar or ionic solvents. The validity of linear response approximations to calculate the time-dependent Stokes shift is evaluated in each system. In most studied systems linear response theory fails. In ionic liquids the magnitude of the overall response is largely overestimated, and linear response theory is not able to capture the individual contributions of cations and anions. In polar liquids, the timescales of solvation dynamics are often not correctly reproduced. These observations are complemented by a detailed analysis of Gaussian statistics including higher order correlation functions, variance of the energy gap distribution and its time evolution. The analysis of higher order correlation functions was found to be not suitable to predict a failure of linear response theory. Further analysis of radial distribution functions and hydrogen bonds in the ground and excited state, as well as the time evolution of the number of hydrogen bonds after solute excitation reveal an influence of solvent structure in some of the studied systems.
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Affiliation(s)
- Esther Heid
- University of Vienna , Faculty of Chemistry , Department of Computational Biological Chemistry , Währingerstraße 19 , A-1090 Vienna , Austria . ; Tel: +43 14277 52711
| | - Christian Schröder
- University of Vienna , Faculty of Chemistry , Department of Computational Biological Chemistry , Währingerstraße 19 , A-1090 Vienna , Austria . ; Tel: +43 14277 52711
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