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Zou M, Hassan Y, Roy TK, McCoy AB, Lester MI. Infrared spectroscopy of the syn-methyl-substituted Criegee intermediate: A combined experimental and theoretical study. J Chem Phys 2024; 160:204309. [PMID: 38818894 DOI: 10.1063/5.0210122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Accepted: 05/06/2024] [Indexed: 06/01/2024] Open
Abstract
An IR-vacuum ultraviolet (VUV) ion-dip spectroscopy method is utilized to examine the IR spectrum of acetaldehyde oxide (CH3CHOO) in the overtone CH stretch (2νCH) spectral region. IR activation creates a depletion of the ground state population that reduces the VUV photoionization signal on the parent mass channel. IR activation of the more stable and populated syn-CH3CHOO conformer results in rapid unimolecular decay to OH + vinoxy products and makes the most significant contribution to the observed spectrum. The resultant IR-VUV ion-dip spectrum of CH3CHOO is similar to that obtained previously for syn-CH3CHOO using IR action spectroscopy with UV laser-induced fluorescence detection of OH products. The prominent IR features at 5984 and 6081 cm-1 are also observed using UV + VUV photoionization of OH products. Complementary theoretical calculations utilizing a general implementation of second-order vibrational perturbation theory provide new insights on the vibrational transitions that give rise to the experimental spectrum in the overtone CH stretch region. The introduction of physically motivated small shifts of the harmonic frequencies yields remarkably improved agreement between experiment and theory in the overtone CH stretch region. The prominent features are assigned as highly mixed states with contributions from two quanta of CH stretch and/or a combination of CH stretch with an overtone in mode 4. The generality of this approach is demonstrated by applying it to three different levels of electronic structure theory/basis sets, all of which provide spectra that are virtually indistinguishable despite showing large deviations prior to introducing the shifts to the harmonic frequencies.
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Affiliation(s)
- Meijun Zou
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Yarra Hassan
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
| | - Tarun Kumar Roy
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
| | - Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA
| | - Marsha I Lester
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
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2
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Mohamed A, Rana A, Perez E, Dahlmann F, Fry A, Menges FS, van Stipdonk M, Jäger S, Boyer MA, McCoy AB, Johnson MA. Characterization of the Oxazolone and Macrocyclic Motifs in the b n ( n = 2-5) Product Ions from Collision-Induced Dissociation of Protonated Oligoglycine Peptides with Isomer-Selective, Cryogenic Vibrational Spectroscopy. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:326-332. [PMID: 38150530 DOI: 10.1021/jasms.3c00372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2023]
Abstract
Collision-induced dissociation (CID) of small, protonated peptides leads to the formation of b-type fragment ions that can occur with several structural motifs driven by different covalent intramolecular bonding arrangements. Here, we characterize the so-called "oxazolone" and "macrocycle" bn ion structures that occur upon CID of oligoglycine peptides (Gn) ions (n = 2-6). This is determined by acquiring the vibrational band patterns of the cryogenically cooled, D2-tagged bn ions obtained using isomer-selective, two-color IR-IR photobleaching and analyzing them with predicted (DFT) harmonic spectra for the candidate structures. Both oxazolone and macrocyclic isomers are formed by b4, whereas only oxazolone species are created for b2 and b3 and the macrocycle is created for b5. As such, n = 4 corresponds to the minimum size where both Oxa and MC forms are present.
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Affiliation(s)
- Ahmed Mohamed
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Abhijit Rana
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Evan Perez
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- The University of Utah, 315 S. 1400 E. Rm 2020, Henry Eyring Bldg, Salt Lake City, Utah 84112, United States
| | - Franziska Dahlmann
- Institut for Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria
| | - Allison Fry
- Center of Excellence in Mass Spectrometry, Center for Metal Ions in Biological and Chemical Systems, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Fabian S Menges
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Michael van Stipdonk
- Center of Excellence in Mass Spectrometry, Center for Metal Ions in Biological and Chemical Systems, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, United States
| | - Svenja Jäger
- Chair of Physical Chemistry II, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany
| | - Mark A Boyer
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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Mandal I, Karimova NV, Zakai I, Gerber RB. Formation of Chlorine in the Atmosphere by Reaction of Hypochlorous Acid with Seawater. J Phys Chem Lett 2024; 15:432-438. [PMID: 38189241 PMCID: PMC11139381 DOI: 10.1021/acs.jpclett.3c03035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/16/2023] [Accepted: 12/20/2023] [Indexed: 01/09/2024]
Abstract
The highly reactive dihalogens play a significant role in the oxidative chemistry of the troposphere. One of the main reservoirs of these halogens is hypohalous acids, HOX, which produce dihalogens in the presence of halides (Y-), where X, Y = Cl, Br, I. These reactions occur in and on aerosol particles and seawater surfaces and have been studied experimentally and by field observations. However, the mechanisms of these atmospheric reactions are still unknown. Here, we establish the atomistic mechanism of HOCl + Cl- → Cl2 + OH- at the surface of the water slab by performing ab initio molecular dynamics (AIMD) simulations. Main findings are (1) This reaction proceeds by halogen-bonded complexes of (HOCl)···(Cl-)aq surrounded with the neighboring water molecules. (2) The halogen bonded (HOCl)···(Cl-)aq complexes undergo charge transfer from Cl- to OH- to form transient Cl2 at neutral pH. (3) The addition of a proton to one proximal water greatly facilitates the Cl2 formation, which explains the enhanced rate at low pH.
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Affiliation(s)
- Imon Mandal
- The
Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Natalia V. Karimova
- Department
of Chemistry, University of California, Irvine, California 92697, United States
| | - Itai Zakai
- The
Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - R. Benny Gerber
- The
Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
- Department
of Chemistry, University of California, Irvine, California 92697, United States
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4
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Khuu T, Schleif T, Mohamed A, Mitra S, Johnson MA, Valdiviezo J, Heindel JP, Head-Gordon T. Intra-cluster Charge Migration upon Hydration of Protonated Formic Acid Revealed by Anharmonic Analysis of Cold Ion Vibrational Spectra. J Phys Chem A 2023; 127:7501-7509. [PMID: 37669457 DOI: 10.1021/acs.jpca.3c03971] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
The rates of many chemical reactions are accelerated when carried out in micron-sized droplets, but the molecular origin of the rate acceleration remains unclear. One example is the condensation reaction of 1,2-diaminobenzene with formic acid to yield benzimidazole. The observed rate enhancements have been rationalized by invoking enhanced acidity at the surface of methanol solvent droplets with low water content to enable protonation of formic acid to generate a cationic species (protonated formic acid or PFA) formed by attachment of a proton to the neutral acid. Because PFA is the key feature in this reaction mechanism, vibrational spectra of cryogenically cooled, microhydrated PFA·(H2O)n=1-6 were acquired to determine how the extent of charge localization depends on the degree of hydration. Analysis of these highly anharmonic spectra with path integral ab initio molecular dynamics simulations reveals the gradual displacement of the excess proton onto the water network in the microhydration regime at low temperatures with n = 3 as the tipping point for intra-cluster proton transfer.
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Affiliation(s)
- Thien Khuu
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Tim Schleif
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Ahmed Mohamed
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Sayoni Mitra
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Jesús Valdiviezo
- Pitzer Theory Center, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Joseph P Heindel
- Pitzer Theory Center, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Teresa Head-Gordon
- Pitzer Theory Center, Department of Chemistry, University of California, Berkeley, California 94720, United States
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Pastorczak M, Duk K, Shahab S, Kananenka AA. Combinational Vibration Modes in H 2O/HDO/D 2O Mixtures Detected Thanks to the Superior Sensitivity of Femtosecond Stimulated Raman Scattering. J Phys Chem B 2023. [PMID: 37201478 DOI: 10.1021/acs.jpcb.3c01334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Overtones and combinational modes frequently play essential roles in ultrafast vibrational energy relaxation in liquid water. However, these modes are very weak and often overlap with fundamental modes, particularly in isotopologues mixtures. We measured VV and HV Raman spectra of H2O and D2O mixtures with femtosecond stimulated Raman scattering (FSRS) and compared the results with calculated spectra. Specifically, we observed the mode at around 1850 cm-1 and assigned it to H-O-D bend + rocking libration. Second, we found that the H-O-D bend overtone band and the OD stretch + rocking libration combination band contribute to the band located between 2850 and 3050 cm-1. Furthermore, we assigned the broad band located between 4000 and 4200 cm-1 to be composed of combinational modes of high-frequency OH stretching modes with predominantly twisting and rocking librations. These results should help in a proper interpretation of Raman spectra of aqueous systems as well as in the identification of vibrational relaxation pathways in isotopically diluted water.
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Affiliation(s)
- Marcin Pastorczak
- Institute of Physical Chemistry, Polish Academy of Sciences, Laser Centre, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Katsiaryna Duk
- Institute of Physical Chemistry, Polish Academy of Sciences, Laser Centre, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Samaneh Shahab
- Institute of Physical Chemistry, Polish Academy of Sciences, Laser Centre, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Alexei A Kananenka
- Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, United States
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6
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Stropoli SJ, Greis K, Schleif T, Johnson MA. Characterization of Oxidation Products from HOCl Uptake by Microhydrated Methionine Anions Using Cryogenic Ion Vibrational Spectroscopy. J Phys Chem A 2023; 127:4269-4276. [PMID: 37133983 DOI: 10.1021/acs.jpca.3c00509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The oxidation of the amino acid methionine (Met) by hypochlorous acid (HOCl) to yield methionine sulfoxide (MetO) has been implicated in both the interfacial chemistry of tropospheric sea spray aerosols and the destruction of pathogens in the immune system. Here, we investigate the reaction of deprotonated methionine water clusters, Met-·(H2O)n, with HOCl and characterize the resulting products using cryogenic ion vibrational spectroscopy and electronic structure calculations. Capture of the MetO- oxidation product in the gas phase requires the presence of water molecules attached to the reactant anion. Analysis of its vibrational band pattern confirms that the sulfide group of Met- has indeed been oxidized. Additionally, the vibrational spectrum of the anion corresponding to the uptake of HOCl by Met-·(H2O)n indicates that it exists as an "exit-channel" complex in which the Cl- product ion is bound to the COOH group following the formation of the S═O motif.
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Affiliation(s)
- Santino J Stropoli
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Kim Greis
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
- Institut für Chemie und Biochemie, Freie Universität Berlin, Altensteinstraße 23A, 14195 Berlin, Germany
- Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
| | - Tim Schleif
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
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Khuu T, Rana A, Edington SC, Yang N, McCoy AB, Johnson MA. Observation of Slow Eigen-Zundel Interconversion in H +(H 2O) 6 Clusters upon Isomer-Selective Vibrational Excitation and Buffer Gas Cooling in a Cryogenic Ion Trap. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:737-744. [PMID: 36972483 DOI: 10.1021/jasms.3c00007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
The formation of isomers when trapping floppy cluster ions in a temperature-controlled ion trap is a generally observed phenomenon. This involves collisional quenching of the ions initially formed at high temperature by buffer gas cooling until their internal energies fall below the barriers in the potential energy surface that separate them. Here we explore the kinetics at play in the case of the two isomers adopted by the H+(H2O)6 cluster ion that differ in the proton accommodation motif. One of these is most like the Eigen cation with a tricoordinated hydronium motif (denoted E), and the other is most like the Zundel ion with the proton equally shared between two water molecules (denoted Z). After initial cooling to about 20 K in the radiofrequency (Paul) trap, the relative populations of these two spectroscopically distinct isomers are abruptly changed through isomer-selective photoexcitation of bands in the OH stretching region with a pulsed (∼6 ns) infrared laser while the ions are in the trap. We then monitor the relaxation of the vibrationally excited clusters and reformation of the two cold isomers by recording infrared photodissociation spectra with a second IR laser as a function of delay time from the initial excitation. The latter spectra are obtained after ejecting the trapped ions into a time-of-flight photofragmentation mass spectrometer, thus enabling long (∼0.1 s) delay times. Excitation of the Z isomer is observed to display long-lived vibrationally excited states that are collisionally cooled on a ms time scale, some of which quench into the E isomer. These excited E species then display spontaneous interconversion to the Z form on a ∼10 ms time scale. These qualitative observations set the stage for a series of experimental measurements that can provide quantitative benchmarks for theoretical simulations of cluster dynamics and the potential energy surfaces that underlie them.
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Affiliation(s)
- Thien Khuu
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Abhijit Rana
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Sean C Edington
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Nan Yang
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Anne B McCoy
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
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