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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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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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Agarwal P, Nieuwoudt MK, Li S, Procter G, Andrews GP, Jones DS, Svirskis D. Exploiting Hydrogen Bonding to Enhance Lidocaine Loading and Stability in a Poly Ethylene-co-Vinyl acetate Carrier Matrix. Int J Pharm 2022; 621:121819. [DOI: 10.1016/j.ijpharm.2022.121819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 05/06/2022] [Accepted: 05/07/2022] [Indexed: 10/18/2022]
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Zhang X, Zhou S, Leonik FM, Wang L, Kuroda DG. Quantum mechanical effects in acid–base chemistry. Chem Sci 2022; 13:6998-7006. [PMID: 35774178 PMCID: PMC9200130 DOI: 10.1039/d2sc01784a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 05/17/2022] [Indexed: 01/04/2023] Open
Abstract
Acid–base chemistry has immense importance for explaining and predicting the chemical products formed by an acid and a base when mixed together. However, the traditional chemistry theories used to describe acid–base reactions do not take into account the effect arising from the quantum mechanical nature of the acidic hydrogen shuttling potential and its dependence on the acid base distance. Here, infrared and NMR spectroscopies, in combination with first principles simulations, are performed to demonstrate that quantum mechanical effects, including electronic and nuclear quantum effects, play an essential role in defining the acid–base chemistry when 1-methylimidazole and acetic acid are mixed together. In particular, it is observed that the acid and the base interact to form a complex containing a strong hydrogen bond, in which the acidic hydrogen atom is neither close to the acid nor to the base, but delocalized between them. In addition, the delocalization of the acidic hydrogen atom in the complex leads to characteristic IR and NMR signatures. The presence of a hydrogen delocalized state in this simple system challenges the conventional knowledge of acid–base chemistry and opens up new avenues for designing materials in which specific properties produced by the hydrogen delocalized state can be harvested. Acid-based theories do not consider the quantum mechanical nature of the acidic hydrogen shuttling potential. Here, it is demonstrated that this particularity is needed to explain the formation acid-base complex with a delocalized acidic hydrogen.![]()
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Affiliation(s)
- Xiaoliu Zhang
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Shengmin Zhou
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Fedra M. Leonik
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Lu Wang
- Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Daniel G. Kuroda
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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Chen L, Fournier JA. Probing Hydrogen-Bonding Interactions within Phenol-Benzimidazole Proton-Coupled Electron Transfer Model Complexes with Cryogenic Ion Vibrational Spectroscopy. J Phys Chem A 2021; 125:9288-9297. [PMID: 34652915 DOI: 10.1021/acs.jpca.1c05879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydrogen-bonding interactions within a series of phenol-benzimidazole model proton-coupled electron transfer (PCET) dyad complexes are characterized using cryogenic ion vibrational spectroscopy. A highly red-shifted and surprisingly broad (>1000 cm-1) transition is observed in one of the models and assigned to the phenolic OH stretch strongly H-bonded to the N(3) benzimidazole atom. The breadth is attributed to a combination of anharmonic Fermi-resonance coupling between the OH stretch and background doorway states involving OH bending modes and strong coupling of the OH stretch frequency to structural deformations along the proton-transfer coordinate accessible at the vibrational zero-point level. The other models show unexpected protonation of the benzimidazole group upon electrospray ionization instead of at more basic remote amine/amide groups. This leads to the formation of HO-+HN(3) H-bond motifs that are much weaker than the OH-N(3) H-bond arrangement. H-bonding between the N(1)H+ benzimidazole group and the carbonyl on the tyrosine backbone is the stronger and preferred interaction in these complexes. The results show that conjugation effects, secondary H-bond interactions, and H-bond soft modes strongly influence the OH-N(3) interaction and highlight the importance of the direct monitoring of proton stretch transitions in characterizing the proton-transfer reaction coordinate in PCET systems.
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Affiliation(s)
- Liangyi Chen
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Joseph A Fournier
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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Sibert EL, Blodgett KN, Zwier TS. Spectroscopic Manifestations of Indirect Vibrational State Mixing: Novel Anharmonic Effects on a Prereactive H Atom Transfer Surface. J Phys Chem A 2021; 125:7318-7330. [PMID: 34382795 DOI: 10.1021/acs.jpca.1c04264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The NH stretch region of the IR spectrum of methyl anthranilate is modeled in the S1 state to understand the connection between the absence of this fundamental in the fluorescence-dip infrared spectra of Blodgett et al. [Phys. Chem. Chem. Phys. 2020, 22, 14077] and its relevance to the H atom dislocation that occurs upon electronic excitation. A set of coordinates are chosen that highlight the role of certain low-frequency modes. A Hamiltonian is developed in which a large-amplitude two-dimensional surface describing the H-bonded H atom is linearly and quadratically coupled to the remaining degrees of freedom which are treated at the harmonic level. The surface is calculated within the time-dependent density functional theory framework by using the B3LYP/6-311++(d, p) level of theory with dispersion. Our spectral results show that indirect couplings lead to massive intensity sharing over hundreds of wavenumbers. This sharing is predicted to be dramatically reduced upon deuteration. The spectral broadening mechanism is found to involve off-resonant doorway states that are themselves strongly coupled to states nearly degenerate with the NH stretch fundamental and represents a complementary mechanism to previous explanations based on Fermi resonance or the presence of Franck-Condon like combination bands with low-frequency motions. Consistent with the spectra predictions, time-dependent calculations show that if the NH stretch fundamental were excited with an ultrafast laser, it would decay within 40 fs. The competition between H atom dislocation and vibrational relaxation is discussed.
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Affiliation(s)
- Edwin L Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Karl N Blodgett
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, United States
| | - Timothy S Zwier
- Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551, 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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Asfin RE. IR Spectra of Hydrogen-Bonded Complexes of Trifluoroacetic Acid with Acetone and Diethyl Ether in the Gas Phase. Interaction between CH and OH Stretching Vibrations. J Phys Chem A 2019; 123:3285-3292. [PMID: 30916959 DOI: 10.1021/acs.jpca.8b10215] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The spectra of complexes of trifluoroacetic acid (TFA) with acetone and diethyl ether (DEE) and their perdeuterated isotopologues were extracted from the spectra of the mixture of the compounds recorded at room temperature. The ν(OH) bands of the complexes with protiated and deuterated acetone notably differ from each other, whereas these ν(OH) bands are practically not affected by the deuteration of DEE. An assumption about the interaction of CH and OH groups in the (CH3)-C═O···HO fragment is made. According to density functional theory calculations, complexes of TFA with both acetone and DEE have a cyclic structure with one strong ═O···HO hydrogen bond and one weak CH···O═ bond. The structural, spectroscopic, and electronic properties indicate an essential role of weak bonds in the total complexation energy of the systems studied.
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Affiliation(s)
- Ruslan E Asfin
- Department of Physics , Saint Petersburg State University , 7/9 Universitetskaya Nab. , 199034 Saint Petersburg , Russian Federation
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9
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Sibert EL. Modeling vibrational anharmonicity in infrared spectra of high frequency vibrations of polyatomic molecules. J Chem Phys 2019; 150:090901. [DOI: 10.1063/1.5079626] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Edwin L. Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Van Hoozen BL, Petersen PB. Vibrational tug-of-war: The pKAdependence of the broad vibrational features of strongly hydrogen-bonded carboxylic acids. J Chem Phys 2018; 148:134309. [PMID: 29626887 DOI: 10.1063/1.5026675] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Brian L. Van Hoozen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | - Poul B. Petersen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
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