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Dean JLS, Winkler VS, Boyer MA, Sibert EL, Fournier JA. Investigating Intramolecular H Atom Transfer Dynamics in β-Diketones with Ultrafast Infrared Spectroscopies and Theoretical Modeling. J Phys Chem A 2023; 127:9258-9272. [PMID: 37882618 DOI: 10.1021/acs.jpca.3c05417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2023]
Abstract
The vibrational signatures and ultrafast dynamics of the intramolecular H-bond in a series of β-diketones are investigated with 2D IR spectroscopy and computational modeling. The chosen β-diketones exhibit a range of H atom donor-acceptor distances and asymmetry along the H atom transfer coordinate that tunes the intramolecular H-bond strength. The species with the strongest H-bonds are calculated to have very soft H atom potentials, resulting in highly red-shifted OH stretch fundamental frequencies and dislocation of the H atom upon vibrational excitation. These soft potentials lead to significant coupling to the other normal mode coordinates and give rise to the very broad vibrational signatures observed experimentally. The 2D IR spectra in both the OH and OD stretch regions of the light and deuterated isotopologues reveal broadened and long-lived ground-state bleach signatures of the vibrationally hot molecules. Polarization-sensitive transient absorption measurements in the OH and OD stretch regions reveal notable isotopic differences in orientational dynamics. Orientational relaxation was measured to occur on ∼600 fs and ∼2 ps time scales for the light and deuterated isotopologues, respectively. The orientational dynamics are interpreted in terms of activated H/D atom transfer events driven by collective intramolecular structural rearrangements.
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Affiliation(s)
- Jessika L S Dean
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Valerie S Winkler
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Mark A Boyer
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin Madison, Madison, Wisconsin 53706, United States
| | - Edwin L Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin Madison, Madison, Wisconsin 53706, United States
| | - Joseph A Fournier
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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2
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Soley M, Videla PE, Nibbering ETJ, Batista VS. Ultrafast Charge Relocation Dynamics in Enol-Keto Tautomerization Monitored with a Local Soft-X-ray Probe. J Phys Chem Lett 2022; 13:8254-8263. [PMID: 36018775 PMCID: PMC9465716 DOI: 10.1021/acs.jpclett.2c02037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 08/18/2022] [Indexed: 06/15/2023]
Abstract
Proton-coupled electron transfer (PCET) is the underlying mechanism governing important reactions ranging from water splitting in photosynthesis to oxygen reduction in hydrogen fuel cells. The interplay of proton and electronic charge distribution motions can vary from sequential to concerted schemes, with elementary steps occurring on ultrafast time scales. We demonstrate with a simulation study that femtosecond soft-X-ray spectroscopy provides key insights into the PCET mechanism of a photoinduced intramolecular enol* → keto* tautomerization reaction. A full quantum treatment of the electronic and nuclear dynamics of 2-(2'-hydroxyphenyl)benzothiazole upon electronic excitation reveals how spectral signatures of local excitations from core to frontier orbitals display the distinctly different stages of charge relocation for the H atom, donating, and accepting sites. Our findings indicate that ultraviolet/X-ray pump-probe spectroscopy provides a unique way to probe ultrafast electronic structure rearrangements in photoinduced chemical reactions essential to understanding the mechanism of PCET.
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Affiliation(s)
- Micheline
B. Soley
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
- Yale
Quantum Institute, Yale University, P.O. Box 208334, New Haven, Connecticut 06520-8263, United States
| | - Pablo E. Videla
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
- Energy
Sciences Institute, Yale University, P.O. Box 27394, West Haven, Connecticut 06516-7394, United States
| | - Erik T. J. Nibbering
- Max
Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max Born Strasse 2A, 12489 Berlin, Germany
| | - Victor S. Batista
- Department
of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, United States
- Yale
Quantum Institute, Yale University, P.O. Box 208334, New Haven, Connecticut 06520-8263, United States
- Energy
Sciences Institute, Yale University, P.O. Box 27394, West Haven, Connecticut 06516-7394, United States
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3
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Carbon dots on paper for determination of Cu2+ in sugar cane spirits samples for fluorescence digital image-based method. Microchem J 2022. [DOI: 10.1016/j.microc.2022.107500] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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4
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Dean JLS, Fournier JA. Vibrational Dynamics of the Intramolecular H-Bond in Acetylacetone Investigated with Transient and 2D IR Spectroscopy. J Phys Chem B 2022; 126:3551-3562. [PMID: 35536173 DOI: 10.1021/acs.jpcb.2c00793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Acetylacetone (AcAc) has proven to be a fruitful but highly challenging model system for the experimental and computational interrogation of strong intramolecular hydrogen bonds. Key questions remain, however, regarding the identity of the minimum-energy structure of AcAc and the dynamics of intramolecular proton transfer. Here, we investigate the OH/OD stretch and bend regions of the enol tautomer of AcAc and its deuterated isotopologue with transient absorption and 2D IR spectroscopy. The OH bend region reveals a single dominant diagonal transition near 1625 cm-1 with intense cross peaks to lower-frequency modes, demonstrating highly mixed fingerprint transitions that contain OH bend character. The anharmonic coupling of the OH bend results in a highly elongated OH bend excited-state absorption transition that indicates a large manifold of OH bend overtone/combination bands in the OH stretch region that leads to strong bend-stretch Fermi resonance interactions. The OH and OD stretch regions consist of broad ground-state bleach signals, but there is no clear evidence of ω21 excited-state absorptions due to rapid population relaxation arising from strong intramolecular coupling to bending, fingerprint, and low-frequency H-bond modes. Orientational relaxation dynamics persist for timescales longer than the vibrational lifetimes, with polarization anisotropy components decaying within approximately 2 and 10 periods of the O-O oscillation for the OH and OD stretch, respectively. The significant isotopic dependence of the orientational dynamics is discussed in the context of intramolecular mode coupling, diffusional processes, and contributions from proton/deuteron transfer dynamics.
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Affiliation(s)
- Jessika L S Dean
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, United States 63130
| | - Joseph A Fournier
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, United States 63130
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Loe CM, Liekhus-Schmaltz C, Govind N, Khalil M. Spectral Signatures of Ultrafast Excited-State Intramolecular Proton Transfer from Computational Multi-edge Transient X-ray Absorption Spectroscopy. J Phys Chem Lett 2021; 12:9840-9847. [PMID: 34606267 DOI: 10.1021/acs.jpclett.1c02483] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Excited-state intramolecular proton transfer (ESIPT) is a fundamental chemical process with several applications. Ultrafast ESIPT involves coupled electronic and atomic motions and has been primarily studied using femtosecond optical spectroscopy. X-ray spectroscopy is particularly useful because it is element-specific and enables direct, individual probes of the proton-donating and -accepting atoms. Herein, we report a computational study to resolve the ESIPT in 10-hydroxybenzo[h]quinoline (HBQ), an intramolecularly hydrogen bonded compound. We use linear-response time-dependent density functional theory (LR-TDDFT) combined with ab initio molecular dynamics (AIMD) and time-resolved X-ray absorption spectroscopy (XAS) computations to track the ultrafast excited-state dynamics. Our results reveal clear X-ray spectral signatures of coupled electronic and atomic motions during and following ESIPT at the oxygen and nitrogen K-edge, paving the way for future experiments at X-ray free electron lasers.
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Affiliation(s)
- Caroline M Loe
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | | | - Niranjan Govind
- Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Munira Khalil
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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Sensitivity of Intra- and Intermolecular Interactions of Benzo[h]quinoline from Car-Parrinello Molecular Dynamics and Electronic Structure Inspection. Int J Mol Sci 2021; 22:ijms22105220. [PMID: 34069244 PMCID: PMC8156133 DOI: 10.3390/ijms22105220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/03/2021] [Accepted: 05/05/2021] [Indexed: 01/29/2023] Open
Abstract
The O-H...N and O-H...O hydrogen bonds were investigated in 10-hydroxybenzo[h]quinoline (HBQ) and benzo[h]quinoline-2-methylresorcinol complex in vacuo, solvent and crystalline phases. The chosen systems contain analogous donor and acceptor moieties but differently coupled (intra- versus intermolecularly). Car–Parrinello molecular dynamics (CPMD) was employed to shed light onto principle components of interactions responsible for the self-assembly. It was applied to study the dynamics of the hydrogen bonds and vibrational features as well as to provide initial geometries for incorporation of quantum effects and electronic structure studies. The vibrational features were revealed using Fourier transformation of the autocorrelation function of atomic velocity and by inclusion of nuclear quantum effects on the O-H stretching solving vibrational Schrödinger equation a posteriori. The potential of mean force (Pmf) was computed for the whole trajectory to derive the probability density distribution and for the O-H stretching mode from the proton vibrational eigenfunctions and eigenvalues incorporating statistical sampling and nuclear quantum effects. The electronic structure changes of the benzo[h]quinoline-2-methylresorcinol dimer and trimers were studied based on Constrained Density Functional Theory (CDFT) whereas the Electron Localization Function (ELF) method was applied for all systems. It was found that the bridged proton is localized on the donor side in both investigated systems in vacuo. The crystalline phase simulations indicated bridged proton-sharing and transfer events in HBQ. These effects are even more pronounced when nuclear quantization is taken into account, and the quantized Pmf allows the proton to sample the acceptor area more efficiently. The CDFT indicated the charge depletion at the bridged proton for the analyzed dimer and trimers in solvent. The ELF analysis showed the presence of the isolated proton (a signature of the strongest hydrogen bonds) only in some parts of the HBQ crystal simulation. The collected data underline the importance of the intramolecular coupling between the donor and acceptor moieties.
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Rabe EJ, Goldwyn HJ, Hwang D, Masiello DJ, Schlenker CW. Intermolecular Hydrogen Bonding Tunes Vibronic Coupling in Heptazine Complexes. J Phys Chem B 2020; 124:11680-11689. [PMID: 33315409 DOI: 10.1021/acs.jpcb.0c07719] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To better understand how hydrogen bonding influences the excited-state landscapes of aza-aromatic materials, we studied hydrogen-bonded complexes of 2,5,8-tris (4-methoxyphenyl)-1,3,4,6,7,9,9b-heptaazaphenalene (TAHz), a molecular photocatalyst related to graphitic carbon nitride, with a variety of phenol derivatives (R-PhOH). By varying the electron-withdrawing character of the para-substituent on the phenol, we can modulate the strength of the hydrogen bond. Using time-resolved photoluminescence, we extract a spectral component associated with the R-PhOH-TAHz hydrogen-bonded complex. Surprisingly, we noticed a striking change in the relative amplitude of vibronic peaks in the TAHz-centered emission as a function of R-group on phenol. To gain a physical understanding of these spectral changes, we employed a displaced-oscillator model of molecular emission to fit these spectra. This fit assumes that two vibrational modes are dominantly coupled to the emissive electronic transition and extracts their frequencies and relative nuclear displacements (related to the Huang-Rhys factor). With the aid of quantum chemical calculations, we found that heptazine ring-breathing and ring-puckering modes are likely responsible for the observed vibronic progression, and both modes indicate decreasing molecular distortion in the excited state with increasing hydrogen bond strength. This finding offers new insights into intermolecular excited-state hydrogen bonding, which is a crucial step toward controlling excited-state proton-coupled electron transfer and proton transfer reactions.
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Affiliation(s)
- Emily J Rabe
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Harrison J Goldwyn
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Doyk Hwang
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - David J Masiello
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Cody W Schlenker
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.,Molecular Engineering and Sciences Institute, University of Washington, Seattle, Washington 98195-1652, United States.,Clean Energy Institute, University of Washington, Seattle, Washington 98195-1653, United States
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Malm C, Prädel LA, Marekha BA, Grechko M, Hunger J. Composition-Dependent Hydrogen-Bonding Motifs and Dynamics in Brønsted Acid-Base Mixtures. J Phys Chem B 2020; 124:7229-7238. [PMID: 32701282 PMCID: PMC7443859 DOI: 10.1021/acs.jpcb.0c04714] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
In
recent years the interaction of organophosphates and imines,
which is at the core of Brønsted acid organocatalysis, has been
established to be based on strong ionic hydrogen bonds. Yet, besides
the formation of homodimers consisting of two acid molecules and heterodimers
consisting of one acid and one base, also multimeric molecular aggregates
are formed in solution. These multimeric aggregates consist of one
base and several acid molecules. The details of the intermolecular
bonding in such aggregates, however, have remained elusive. To characterize
composition-dependent bonding and bonding dynamics in these aggregates,
we use linear and nonlinear infrared (IR) spectroscopy at varying
molar ratios of diphenyl phosphoric acid and quinaldine. We identify
the individual aggregate species, giving rise to the structured, strong,
and very broad infrared absorptions, which span more than 1000 cm–1. Linear infrared spectra and density functional theory
calculations of the proton transfer potential show that doubly ionic
intermolecular hydrogen bonds between the acid and the base lead to
absorptions which peak at ∼2040 cm–1. The
contribution of singly ionic hydrogen bonds between an acid anion
and an acid molecule is observed at higher frequencies. As common
to such strong hydrogen bonds, ultrafast IR spectroscopy reveals rapid,
∼ 100 fs, dissipation of energy from the proton transfer coordinate.
Yet, the full dissipation of the excess energy occurs on a ∼0.8–1.1
ps time scale, which becomes longer when multimers dominate. Our results
thus demonstrate the coupling and collectivity of the hydrogen bonds
within these complexes, which enable efficient energy transfer.
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Affiliation(s)
- Christian Malm
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Leon A Prädel
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Bogdan A Marekha
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Maksim Grechko
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Johannes Hunger
- Max-Planck-Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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Akiva A, Chuntonov L. Intramolecular hydrogen bonding protects the hydroxyl group from attack by fluctuating solvent forces. J Chem Phys 2020; 152:074502. [PMID: 32087624 DOI: 10.1063/1.5143572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ultrafast spectroscopy of molecular systems involving hydrogen- (H-) bonding has been at the forefront of fundamental chemical and physical research for several decades. Among the spectroscopic observables of the ultrafast dynamics is the pure dephasing of vibrationally excited molecules. Using third-order nonlinear vibrational spectroscopy, including polarization-selective transient grating measurements of vibrational lifetime and orientational diffusion as well as two-dimensional infrared spectroscopy, we determined different individual line shape components of hydroxyl stretching (νOH) excitations in a homologous series of chlorophenols and obtained the corresponding pure dephasing rates. The pure dephasing rates are correlated with vibrational anharmonicity of the νOH mode, which is tuned remotely from the hydroxyl site by changing the position of the chlorine substituents on the phenol ring. We found that in molecules where the hydroxyl group is in its free form, the pure dephasing rates scale linearly with the mode's anharmonicity such that assuming it is dominated by the third-order diagonal term, the ultrafast dynamics follow the prediction of the Kubo-Oxtoby theory. However, in the intramolecularly H-bonded ortho-chlorophenols, this trend is reversed, and the pure dephasing slows down by ∼50% for an increase in anharmonicity of only a few wavenumbers. Because the νOH mode's anharmonicity is known to reflect the H-bonding strength, our results suggest that intramolecular H-bonding can serve as a mechanism of protection from fluctuating forces exerted by the solvent. Such an effect can be relevant for ultrafast dynamics in biomolecules, where H-bonding plays a central role.
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Affiliation(s)
- Amit Akiva
- Schulich Faculty of Chemistry and Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
| | - Lev Chuntonov
- Schulich Faculty of Chemistry and Solid State Institute, Technion - Israel Institute of Technology, Haifa 3200003, Israel
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Kim J, Kim CH, Burger C, Park M, Kling MF, Kim DE, Joo T. Non-Born-Oppenheimer Molecular Dynamics Observed by Coherent Nuclear Wave Packets. J Phys Chem Lett 2020; 11:755-761. [PMID: 31927968 DOI: 10.1021/acs.jpclett.9b03488] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The reaction dynamics of a photochemical reaction is typically described by reaction coordinates based on the Born-Oppenheimer (BO) approximation. A strong interaction between electrons and nuclei, conventionally occurring at conical intersections, however, breaks the BO approximation and has major consequences for the efficiency of a photochemical reaction. Despite its importance, related studies into the non-BO dynamics are scarce. Here, we investigate the non-BO dynamics of excited-state intramolecular proton transfer (ESIPT) occurring in 10-hydroxybenzo[h]quinoline (HBQ). Two coherent vibrational modes at 237 and 794 cm-1 representing molecular dynamics on a diabatic surface in HBQ are identified by a wave packet analysis based on a transient absorption measurement with a time resolution of 11 fs and with a density functional theory-based model calculation. It is also revealed that the strong Coulomb field effect in HBQ leads to the completion of ESIPT within about two cycles of the OH stretching mode. The work paves the way for time-domain studies of molecular dynamics beyond the BO approximation in other photochemical reactions.
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Affiliation(s)
- JunWoo Kim
- Department of Chemistry , Pohang University of Science and Technology (POSTECH) , Pohang 37673 , Korea
| | - Chul Hoon Kim
- Center for Attosecond Science and Technology , Max Planck POSTECH/Korea Research Initiative (MPK) , Pohang 37673 , Korea
| | - Christian Burger
- Max Plank Institute of Quantum Optics , D-85748 Garching , Germany
- Physics Department , Ludwig-Maximilians-Universität Munich , D-85748 Garching , Germany
| | - Myeongkee Park
- Department of Chemistry , Pohang University of Science and Technology (POSTECH) , Pohang 37673 , Korea
| | - Matthias F Kling
- Max Plank Institute of Quantum Optics , D-85748 Garching , Germany
- Physics Department , Ludwig-Maximilians-Universität Munich , D-85748 Garching , Germany
| | - Dong Eon Kim
- Center for Attosecond Science and Technology , Max Planck POSTECH/Korea Research Initiative (MPK) , Pohang 37673 , Korea
- Department of Physics , Pohang University of Science and Technology (POSTECH) , Pohang 37673 , Korea
| | - Taiha Joo
- Department of Chemistry , Pohang University of Science and Technology (POSTECH) , Pohang 37673 , Korea
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