1
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Park SM, Kwon CH. Deciphering the conformational preference and ionization dynamics of tetrahydrofuran: Insights from advanced spectroscopic techniques. J Chem Phys 2024; 160:114308. [PMID: 38497473 DOI: 10.1063/5.0186570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 03/04/2024] [Indexed: 03/19/2024] Open
Abstract
Tetrahydrofuran (THF) has garnered significant attention due to its pivotal role in biological and chemical processes. The diverse array of conformations exhibited by THF profoundly impacts its reactivity and interactions with other molecules. Understanding these conformational preferences is crucial for comprehending its molecular behavior. In this study, we utilize infrared (IR) resonant vacuum ultraviolet photoionization/mass-analyzed threshold ionization (VUV-PI/MATI) mass spectroscopies to capture distinctive vibrational spectra of individual conformers, namely, "twisted" and "bent," within THF. Our conformer-specific vibrational spectra provide valuable insights into the relative populations of these two conformers. The analysis reveals that the twisted (C2) conformer is more stable than the bent (CS) conformer by 17 ± 15 cm-1. By precisely tuning the VUV photon energy to coincide with vibrational excitation via IR absorption, we selectively ionize specific conformers, yielding two-photon IR + VUV-PI/MATI spectra corresponding to the twisted and bent conformers. This investigation conclusively affirms that both the twisted and bent conformers coexist in the neutral state, while only the twisted conformer exists in the cationic state. These findings not only bridge gaps in existing knowledge but also provide profound insights into the behavior of this pivotal molecule in the realms of biology and medicine.
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Affiliation(s)
- Sung Man Park
- Department of Chemistry and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
| | - Chan Ho Kwon
- Department of Chemistry and Institute for Molecular Science and Fusion Technology, Kangwon National University, Chuncheon 24341, Republic of Korea
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2
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Boyer MA, Sibert EL. A general expression for vibrational Hamiltonians expressed in oblique coordinates. J Chem Phys 2023; 159:234108. [PMID: 38108478 DOI: 10.1063/5.0181135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Accepted: 11/29/2023] [Indexed: 12/19/2023] Open
Abstract
We examine the properties of oblique coordinates. The coordinates, introduced by Zúñiga et al. [J. Phys. B: At., Mol. Opt. Phys. 52, 055101, (2019)], reduce vibrational mode-mixing and enhance the quality of vibrational assignments in quantum mechanical investigations of two-dimensional model Hamiltonians. Oblique coordinates are obtained by making non-orthogonal rotations of the original coordinates that convert the matrix representation of the quadratic Hamiltonian operator into a block-diagonal matrix where the blocks are distinguished by the total quanta of vibrational excitation. Using techniques for the polar decomposition of matrices, we present a scheme for finding these coordinates for systems of arbitrary dimensions. Several molecular examples are presented that highlight the advantages of these coordinates.
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Affiliation(s)
- Mark A Boyer
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Edwin L Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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3
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Neisser RW, Davis JP, Alfieri ME, Harkins H, Petit AS, Tabor DP, Kidwell NM. Photophysical Outcomes of Water-Solvated Heterocycles: Single-Conformation Ultraviolet and Infrared Spectroscopy of Microsolvated 2-Phenylpyrrole. J Phys Chem A 2023; 127:10540-10554. [PMID: 38085923 DOI: 10.1021/acs.jpca.3c04472] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
The molecular chromophores within brown carbon (BrC) aerosols absorb solar radiation at visible and near-ultraviolet wavelengths. This contributes to the overall warming of the troposphere and the photochemical aging of aerosols. In this investigation, we combine a suite of experimental and theoretical methods to reveal the conformation-specific ultraviolet and infrared spectroscopy of 2-phenylpyrrole (2PhPy)─an extended π-conjugated pyrrole derivative and a model BrC chromophore─along with its water microsolvated molecular complexes (2PhPy:nH2O, n = 1-3). Using resonant two-photon ionization and double-resonance holeburning techniques alongside MP3 (ground state) and ADC(3) (excited state) torsional potential energy surfaces and discrete variable representation simulations, we characterized the ultraviolet spectra of 2PhPy and 2PhPy:1H2O. This analysis revealed evidence for Herzberg-Teller vibronic coupling along the CH wagging and NH stretching coordinates of the aromatic rings. Conformation-specific infrared spectroscopy revealed extended hydrogen-bonding networks of the 2PhPy:nH2O complexes. Upon stepwise addition of H2O solvation, the nearest H2O acceptor forms a strong, noncovalent interaction with the pyrrole NH donor, while the second and third H2O partners interface with the phenyl and pyrrole aromatic rings through growing van der Waals π/H atom stabilization. A local-mode Hamiltonian approach was employed for comparison with the experimental spectra, thus identifying the vibrational spectral signatures to specific 2PhPy:nH2O oscillators.
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Affiliation(s)
- Ruby W Neisser
- Department of Chemistry, The College of William & Mary, Williamsburg, Virginia 23187-8795, United States
| | - John P Davis
- Department of Chemistry, The College of William & Mary, Williamsburg, Virginia 23187-8795, United States
| | - Megan E Alfieri
- Department of Chemistry, The College of William & Mary, Williamsburg, Virginia 23187-8795, United States
| | - Hayden Harkins
- Department of Chemistry and Biochemistry, California State University─Fullerton, Fullerton, California 92834-6866, United States
| | - Andrew S Petit
- Department of Chemistry and Biochemistry, California State University─Fullerton, Fullerton, California 92834-6866, United States
| | - Daniel P Tabor
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Nathanael M Kidwell
- Department of Chemistry, The College of William & Mary, Williamsburg, Virginia 23187-8795, United States
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4
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Schweer SM, Gawrilow M, Nejad A, Suhm MA. Formic acid-methanol complexation vs. esterification: elusive pre-reactive species identified by vibrational spectroscopy. Phys Chem Chem Phys 2023; 25:29982-29992. [PMID: 37904580 DOI: 10.1039/d3cp04705a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2023]
Abstract
Vibrational spectra of the mixed dimer and the two mixed trimers of methanol and formic acid as well as some of their isotopologues are presented. Out of the eight expected OH stretching fundamentals of these three pre-reactive hydrogen-bonded complexes, the three modes mainly involving an acid OH group bound to the alcohol appear to be missing in the jet-cooled spectra despite a combination of infrared and Raman probing. A possibility of spectral overlap is discussed in the mixed dimer case, but largely discarded. The missing modes correspond to (fractional) concerted elongation of all engaged OH bonds, promoting synchronous degenerate proton transfer between the molecules. One other trimer mode is very tentatively attributed to a broad spectral feature, whereas all OH bonds contacting carbonyl groups can be unambiguously identified by four relatively narrow infrared absorptions. The spectral features are confirmed by vibrational perturbation theory and deviate in a subtle but systematic way from scaled harmonic predictions which were previously validated for the formic acid complex with a more acidic alcohol. Despite being exothermic and exergonic, ester formation can only be detected in the rarefied gas expansions after extended pre-mixture of the gases, which somewhat contrasts the recent microwave spectroscopic evidence of in situ ester formation and in particular the lack of pre-reactive complex signals.
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Affiliation(s)
- Sophie M Schweer
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
| | - Maxim Gawrilow
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
| | - Arman Nejad
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
| | - Martin A Suhm
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
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5
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Palanisamy N, Banik S. An approximation to the vibrational coupled-cluster method for CH-stretching of large molecules: application to naphthalene and anthracene. Phys Chem Chem Phys 2023; 25:20076-20092. [PMID: 37462438 DOI: 10.1039/d3cp01313h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
We propose an approximation to the vibrational coupled-cluster method (VCCM) to describe the CH-stretching region of the vibrational spectrum of large molecules. The vibrational modes of a molecule are divided into two sets: the target set and the bath set. The target set includes the CH stretches and the modes that are strongly coupled with the CH stretches and/or involve strong Fermi resonances with a CH stretch fundamental. The rest of the modes are in the bath set. First, the effective harmonic oscillator (EHO) approximation is invoked for the whole system to obtain the zeroth-order frequencies and modified potentials. The effects of interaction between the bath set and the target sets are included in the modified potential from the EHO calculation. The VCCM equations are constructed with the modified potential from the EHO calculations and for the target set only. The transition energies and intensities are calculated using such a truncated VCCM approximation. The proposed method is applied to calculate the IR spectra of naphthalene and anthracene. The results with three different criteria for selecting the modes in the target set are compared with the experimental IR spectra.
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Affiliation(s)
- Nivedhitha Palanisamy
- Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India.
| | - Subrata Banik
- Department of Chemistry, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India.
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6
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Foley CD, Allen CD, Au K, Lee C, Rempe SB, Ren P, Sibert EL, Zwier TS. Molecular Cage Reports on Its Contents: Spectroscopic Signatures of Cryo-Cooled K +- and Ba 2+-Benzocryptand Complexes. J Phys Chem A 2023. [PMID: 37478410 DOI: 10.1021/acs.jpca.3c03457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2023]
Abstract
UV photofragment spectroscopy and IR-UV double resonance methods are used to determine the structure and spectroscopic responses of a three-dimensional [2.2.2]-benzocryptand cage to the incorporation of a single K+ or Ba2+ imbedded inside it (labeled as K+-BzCrypt, Ba2+-BzCrypt). We studied the isolated ion-cryptand complex under cryo-cooled conditions, brought into the gas phase by nano-electrospray ionization. Incorporation of a phenyl ring in place of the central ethyl group in one of the three N-CH2-CH2-O-CH2-CH2-O-CH2-CH2-N chains provides a UV chromophore whose S0-S1 transition we probe. K+-BzCrypt and Ba2+-BzCrypt have their S0-S1 origin transitions at 35,925 and 36,446 cm-1, respectively, blue-shifted by 174 and 695 cm-1 from that of 1,2-dimethoxybenzene. These origins are used to excite a single conformation of each complex selectively and record their IR spectra using IR-UV dip spectroscopy. The alkyl CH stretch region (2800-3000 cm-1) is surprisingly sensitive to the presence and nature of the encapsulated ion. We carried out an exhaustive conformational search of cage conformations for K+-BzCrypt and Ba2+-BzCrypt, identifying two conformations (A and B) that lie below all others in energy. We extend our local mode anharmonic model of the CH stretch region to these strongly bound ion-cage complexes to predict conformation-specific alkyl CH stretch spectra, obtaining quantitative agreement with experiment for conformer A, the gas-phase global minimum. The large electrostatic effect of the charge on the O- and N-lone pairs affects the local mode frequencies of the CH2 groups adjacent to these atoms. The localized CH2 scissors modes are pushed up in frequency by the adjacent O/N-atoms so that their overtones have little effect on the alkyl CH stretch region. However, the localized CH2 wags are nearly degenerate and strongly coupled to one another, producing an array of delocalized wag normal modes, whose highest frequency members reach up above 1400 cm-1. As such, their overtones mix significantly with the CH stretch modes, most notably involving the CH2 symmetric stretch fundamentals of the central ethyl groups in the all-alkyl chains and the CH stretches adjacent to the N-atoms and antiperiplanar to the nitrogen lone pair.
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Affiliation(s)
- Casey D Foley
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Cole D Allen
- Department of Biomedical Engineering, University of Texas-Austin, Austin, Texas 78712, United States
| | - Kendrew Au
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Chin Lee
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
| | - Susan B Rempe
- Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | - Pengyu Ren
- Department of Biomedical Engineering, University of Texas-Austin, Austin, Texas 78712, United States
| | - Edwin L Sibert
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Timothy S Zwier
- Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, California 94550, United States
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7
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Kraka E, Quintano M, La Force HW, Antonio JJ, Freindorf M. The Local Vibrational Mode Theory and Its Place in the Vibrational Spectroscopy Arena. J Phys Chem A 2022; 126:8781-8798. [DOI: 10.1021/acs.jpca.2c05962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Elfi Kraka
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas75275-0314, United States
| | - Mateus Quintano
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas75275-0314, United States
| | - Hunter W. La Force
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas75275-0314, United States
| | - Juliana J. Antonio
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas75275-0314, United States
| | - Marek Freindorf
- Computational and Theoretical Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave, Dallas, Texas75275-0314, United States
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8
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Sibert EL, Bernath PF. A local mode study of ring puckering effects in the infrared spectra of cyclopentane. J Chem Phys 2022; 156:214305. [DOI: 10.1063/5.0095010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We report and interpret recently recorded high-resolution infrared spectra for the fundamentals of the CH2 scissors and CH stretches of gas phase cyclopentane at −26.1 and −50 °C, respectively. We extend previous theoretical studies of this molecule, which is known to undergo barrierless pseudorotation due to ring puckering, by constructing local mode Hamiltonians of the stretching and scissor vibrations for which the frequencies, couplings, and linear dipoles are calculated as functions of the pseudorotation angle using B3LYP/6-311++(d,p) and MP2/cc-pVTZ levels of theory. Symmetrization ( D5 h) of the vibrational basis sets leads to simple vibration/pseudorotation Hamiltonians whose solutions lead to good agreement with the experiment at medium resolution, but which miss interesting line fractionation when compared to the high-resolution spectra. In contrast to the scissor motion, pseudorotation leads to significant state mixing of the CH stretches, which themselves are Fermi coupled to the scissor overtones.
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Affiliation(s)
- Edwin L. Sibert
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Peter F. Bernath
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, USA
- Department of Physics, Old Dominion University, Norfolk, Virginia 23529, USA
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9
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Lawler JT, Harrilal CP, DeBlase AF, Sibert EL, McLuckey SA, Zwier TS. Single-conformation spectroscopy of cold, protonated DPG-containing peptides: switching β-turn types and formation of a sequential type II/II' double β-turn. Phys Chem Chem Phys 2022; 24:2095-2109. [PMID: 35019911 DOI: 10.1039/d1cp04852j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
D-Proline (DPro, DP) is widely utilized to form β-hairpin loops in engineered peptides that would otherwise be unstructured, most often as part of a DPG sub-unit that forms a β-turn. To observe whether DPG facilitated this effect in short protonated peptides, conformation specific IR-UV double resonance photofragment spectra of the cold (∼10 K) protonated DP and LP diastereomers of the pentapeptide YAPGA was carried out in the hydride stretch (2800-3700 cm-1) and amide I/II (1400-1800 cm-1) regions. A model localized Hamiltonian was developed to better describe the 1600-1800 cm-1 region commonly associated with the amide I vibrations. The CO stretch fundamentals experience extensive mixing with the N-H bending fundamentals of the NH3+ group in these protonated peptides. The model Hamiltonian accounts for experiment in quantitative detail. In the DP diastereomer, all the population is funneled into a single conformer which presented as a type II β-turn with A and DP in the i + 1 and i + 2 positions, respectively. This structure was not the anticipated type II' β-turn across DPG that we had hypothesized based on solution-phase propensities. Analysis of the conformational energy landscape shows that both steric and charge-induced effects play a role in the preferred formation of the type II β-turn. In contrast, the LP isomer forms three conformations with very different structures, none of which were type II/II' β-turns, confirming that LPG is not a β-turn former. Finally, single-conformation spectroscopy was also carried out on the extended peptide [YAADPGAAA + H]+ to determine whether moving the protonated N-terminus further from DPG would lead to β-hairpin formation. Despite funneling its entire population into a single peptide backbone structure, the assigned structure is not a β-hairpin, but a concatenated type II/type II' double β-turn that displaces the peptide backbone laterally by about 7.5 Å, but leaves the backbone oriented in its original direction.
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Affiliation(s)
- John T Lawler
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | | | - Andrew F DeBlase
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Edwin L Sibert
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706, USA.
| | - Scott A McLuckey
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
| | - Timothy S Zwier
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA. .,Gas Phase Chemical Physics, Sandia National Laboratories, Livermore, CA 94550, USA
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10
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Ozaki Y, Beć KB, Morisawa Y, Yamamoto S, Tanabe I, Huck CW, Hofer TS. Advances, challenges and perspectives of quantum chemical approaches in molecular spectroscopy of the condensed phase. Chem Soc Rev 2021; 50:10917-10954. [PMID: 34382961 DOI: 10.1039/d0cs01602k] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The purpose of this review is to demonstrate advances, challenges and perspectives of quantum chemical approaches in molecular spectroscopy of the condensed phase. Molecular spectroscopy, particularly vibrational spectroscopy and electronic spectroscopy, has been used extensively for a wide range of areas of chemical sciences and materials science as well as nano- and biosciences because it provides valuable information about structure, functions, and reactions of molecules. In the meantime, quantum chemical approaches play crucial roles in the spectral analysis. They also yield important knowledge about molecular and electronic structures as well as electronic transitions. The combination of spectroscopic approaches and quantum chemical calculations is a powerful tool for science, in general. Thus, our article, which treats various spectroscopy and quantum chemical approaches, should have strong implications in the wider scientific community. This review covers a wide area of molecular spectroscopy from far-ultraviolet (FUV, 120-200 nm) to far-infrared (FIR, 400-10 cm-1)/terahertz and Raman spectroscopy. As quantum chemical approaches, we introduce several anharmonic approaches such as vibrational self-consistent field (VSCF) and the combination of periodic harmonic calculations with anharmonic corrections based on finite models, grid-based techniques like the Numerov approach, the Cartesian coordinate tensor transfer (CCT) method, Symmetry-Adapted Cluster Configuration-Interaction (SAC-CI), and the ZINDO (Semi-empirical calculations at Zerner's Intermediate Neglect of Differential Overlap). One can use anharmonic approaches and grid-based approaches for both infrared (IR) and near-infrared (NIR) spectroscopy, while CCT methods are employed for Raman, Raman optical activity (ROA), FIR/terahertz and low-frequency Raman spectroscopy. Therefore, this review overviews cross relations between molecular spectroscopy and quantum chemical approaches, and provides various kinds of close-reality advanced spectral simulation for condensed phases.
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Affiliation(s)
- Yukihiro Ozaki
- School of Biological and Environmental Sciences, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan. and Toyota Physical and Chemical Research Institute, Yokomichi, Nagakute, Aichi 480-1192, Japan
| | - Krzysztof B Beć
- Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Yusuke Morisawa
- Department of Chemistry, School of Science and Engineering, Kindai University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Shigeki Yamamoto
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Ichiro Tanabe
- Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Christian W Huck
- Institute of Analytical Chemistry and Radiochemistry, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Thomas S Hofer
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80-82, A6020 Innsbruck, Austria
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11
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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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12
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Beć KB, Grabska J, Huck CW. Current and future research directions in computer-aided near-infrared spectroscopy: A perspective. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 254:119625. [PMID: 33706116 DOI: 10.1016/j.saa.2021.119625] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/09/2021] [Accepted: 02/09/2021] [Indexed: 06/12/2023]
Abstract
The present review aims to draw a perspective on the vibrational spectroscopy combined with the tools of computational chemistry. This includes an overview of the accomplishments made so far, the assessment of the present development trends and the prospects for continuing these advances. State-of-the-art methods, current challenges and the expected future advances are evaluated from the point-of-view of the practical application in vibrational spectroscopy. A special attention is given to near-infrared (NIR) spectroscopy, which occupies a distinct position among the techniques of vibrational spectroscopy. As the result of intrinsically complex spectra, reliance on the anharmonicity as well as keen interest given to complex materials, NIR spectroscopy may particularly benefit from computational chemistry. The present key limitations hindering development of NIR spectroscopy are identified; these constitute primarily the limit in the treatable system size and the inability to effectively include chemical matrix effects. Given the expanding role of NIR spectroscopy in science and industry, lifting these limitations would directly enhance the general potential of this technique.
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Affiliation(s)
- Krzysztof B Beć
- Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, CCB-Center for Chemistry and Biomedicine, Innrain 80/82, 6020 Innsbruck, Austria
| | - Justyna Grabska
- Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, CCB-Center for Chemistry and Biomedicine, Innrain 80/82, 6020 Innsbruck, Austria.
| | - Christian W Huck
- Institute of Analytical Chemistry and Radiochemistry, Leopold-Franzens University, CCB-Center for Chemistry and Biomedicine, Innrain 80/82, 6020 Innsbruck, Austria
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13
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Barone V, Alessandrini S, Biczysko M, Cheeseman JR, Clary DC, McCoy AB, DiRisio RJ, Neese F, Melosso M, Puzzarini C. Computational molecular spectroscopy. ACTA ACUST UNITED AC 2021. [DOI: 10.1038/s43586-021-00034-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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14
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Weakly RB, Gaynor JD, Khalil M. Multimode two-dimensional vibronic spectroscopy. II. Simulating and extracting vibronic coupling parameters from polarization-selective spectra. J Chem Phys 2021; 154:184202. [PMID: 34241007 DOI: 10.1063/5.0047727] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Experimental demonstrations of polarization-selection two-dimensional Vibrational-Electronic (2D VE) and 2D Electronic-Vibrational (2D EV) spectroscopies aim to map the magnitudes and spatial orientations of coupled electronic and vibrational coordinates in complex systems. The realization of that goal depends on our ability to connect spectroscopic observables with molecular structural parameters. In this paper, we use a model Hamiltonian consisting of two anharmonically coupled vibrational modes in electronic ground and excited states with linear and bilinear vibronic coupling terms to simulate polarization-selective 2D EV and 2D VE spectra. We discuss the relationships between the linear vibronic coupling and two-dimensional Huang-Rhys parameters and between the bilinear vibronic coupling term and Duschinsky mixing. We develop a description of the vibronic transition dipoles and explore how the Hamiltonian parameters and non-Condon effects impact their amplitudes and orientations. Using simulated polarization-selective 2D EV and 2D VE spectra, we show how 2D peak positions, amplitudes, and anisotropy can be used to measure parameters of the vibronic Hamiltonian and non-Condon effects. This paper, along with the first in the series, provides the reader with a detailed description of reading, simulating, and analyzing multimode, polarization-selective 2D EV and 2D VE spectra with an emphasis on extracting vibronic coupling parameters from complex spectra.
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Affiliation(s)
- Robert B Weakly
- Department of Chemistry, University of Washington, P.O. Box 351700, Seattle, Washington 98195, USA
| | - James D Gaynor
- Department of Chemistry, University of Washington, P.O. Box 351700, Seattle, Washington 98195, USA
| | - Munira Khalil
- Department of Chemistry, University of Washington, P.O. Box 351700, Seattle, Washington 98195, USA
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Gui S, Jiang L, Liu ZF. Evolution of the linker in microhydrated hydrogen dinitrate anions: From H + to H 5 O 2. J Comput Chem 2021; 42:1514-1525. [PMID: 33990989 DOI: 10.1002/jcc.26560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Revised: 04/24/2021] [Accepted: 04/27/2021] [Indexed: 11/09/2022]
Abstract
Hydrogen dinitrate anion, HNO3 (NO3 - ), is a proton-bound dimer with a very strong hydrogen bond. By employing ab initio molecular dynamics (AIMD) method, we studied the effects of the proton transfer and the rotation of the nitrates on the vibrational profiles of HNO3 (NO3 - )(H2 O)n (n = 0-2). The AIMD results indicate that the structure of the n = 0 cluster is very flexible, even though its hydrogen bond is quite strong. Significant rotations around the hydrogen bond and frequent transfers of proton from HNO3 to NO3 - are observed in AIMD simulations. Dynamic changes are therefore an important factor in understanding the broadening of vibrational features. For n = 1, the extent of structural fluctuation increases further, as H2 O could move around the anion while the HNO3 (NO3 - ) core also goes through structural changes. Its vibrational spectrum can be understood as a mixture of many isomers visited during AIMD simulations. By n = 2, the structure is stabilized around one isomer, with the linker between the two nitrates being H5 O2 + , rather than H+ . Due to strong hydrogen bonds between nitrates and water molecules, this H5 O2 + takes the extraordinary structure with the H+ localized on one H2 O, rather than being shared. While this novel structure is stable during AIMD simulations, the dynamic fluctuations in hydrogen bond distances still produce significant broadening in its vibrational profile.
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Affiliation(s)
- Shaojun Gui
- Department of Chemistry and Centre for Scientific Modeling and Computation, Chinese University of Hong Kong, Hong Kong, China
| | - Ling Jiang
- State Key Laboratory of Molecular Reaction Dynamics, Collaborative Innovation Center of Chemistry for Energy and Materials (iChEM), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Zhi-Feng Liu
- Department of Chemistry and Centre for Scientific Modeling and Computation, Chinese University of Hong Kong, Hong Kong, China.,CUHK Shenzhen Research Institute, Shenzhen, China
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16
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Yadav S, Banik S, Prasad MD. Understanding of the C-H stretch region of infra-red spectroscopy: an analysis of the final state wavefunctions. Phys Chem Chem Phys 2021; 23:9176-9188. [PMID: 33885051 DOI: 10.1039/d0cp01157f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The nature of the wavefunctions associated with the final states in the CH stretching region of several medium sized molecules is analysed. The number of optically bright transitions is much larger than the number of CH oscillators present in the molecule, and they are spread over a range of about 300 cm-1. Several of them are clustered together within about 5 cm-1 with near equal intensities. The final states of all these transitions are superpositions of multiple zeroth order states. In almost all of such superpositions, no single zeroth order state has more than 50% weight. Several multiquantum states, with three to four quanta of excitation dominate the final states, with the CH chromophore contributing only a small weightage. Thus the band structure of the CH stretch region is due to several optically bright transitions whose final states are superpositions of low frequency multiquantum states with the CH chromophore contributing only a small weight to make them spectroscopically active.
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Affiliation(s)
- Swati Yadav
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India.
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17
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Nejad A, Suhm MA, Meyer KAE. Increasing the weights in the molecular work-out of cis- and trans-formic acid: extension of the vibrational database via deuteration. Phys Chem Chem Phys 2020; 22:25492-25501. [PMID: 33169758 DOI: 10.1039/d0cp04451b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The higher-energy cis- as well as the global minimum trans-rotamers of the four H/D isotopologues of the formic acid monomer have been examined with Raman jet spectroscopy extending the vibrational gas phase reference database by eleven new cis-band positions for HCOOD, DCOOH, and DCOOD. With these new additions, all O-H/D, C-H/D, and C[double bond, length as m-dash]O stretching as well as the O-D in-plane bending vibrations of these higher-energy rotamers are known in addition to the previously determined C-O stretch and OH torsion of cis-HCOOH. Further, a comparison of the vibrational spectra of all four H/D isotopologues of the globally stable trans-rotamer of formic acid is shown to be very helpful in revealing similarities and differences in these systems, particularly with regard to Fermi resonances. Amongst the most prominent ones is the ν5/2ν9 resonance doublet of trans-HCOOH, for which we provide more insight into a recently suggested label switch of the resonance partners via the comparison of infrared and Raman jet spectra.
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Affiliation(s)
- Arman Nejad
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
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18
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Abstract
Three energetically close pairs of vibrational states in glycolic acid are investigated by Raman spectroscopy in a supersonic jet to provide challenging benchmarks for vibrational and electronic structure theory and to solve some open issues in this prototypical hydroxy acid. The alcoholic OH stretching fundamental is located only 8 cm-1 below the acidic OH stretch at 3586 cm-1, much less shifted than predicted by previous anharmonic calculations and by experimental analogy to a fluorene derivative. This and further near-degeneracies in the CH and C=O stretching region are used to assess the predictive power of an exploratory set of quantum chemical calculations including anharmonic VPT2 corrections.
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Affiliation(s)
- Arman Nejad
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Enno Meyer
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
| | - Martin A Suhm
- Institute of Physical Chemistry, University of Göttingen, Tammannstr. 6, 37077 Göttingen, Germany
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19
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Bakels S, Gaigeot MP, Rijs AM. Gas-Phase Infrared Spectroscopy of Neutral Peptides: Insights from the Far-IR and THz Domain. Chem Rev 2020; 120:3233-3260. [PMID: 32073261 PMCID: PMC7146864 DOI: 10.1021/acs.chemrev.9b00547] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
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Gas-phase, double
resonance IR spectroscopy has proven to be an
excellent approach to obtain structural information on peptides ranging
from single amino acids to large peptides and peptide clusters. In
this review, we discuss the state-of-the-art of infrared action spectroscopy
of peptides in the far-IR and THz regime. An introduction to the field
of far-IR spectroscopy is given, thereby highlighting the opportunities
that are provided for gas-phase research on neutral peptides. Current
experimental methods, including spectroscopic schemes, have been reviewed.
Structural information from the experimental far-IR spectra can be
obtained with the help of suitable theoretical approaches such as
dynamical DFT techniques and the recently developed Graph Theory.
The aim of this review is to underline how the synergy between far-IR
spectroscopy and theory can provide an unprecedented picture of the
structure of neutral biomolecules in the gas phase. The far-IR signatures
of the discussed studies are summarized in a far-IR map, in order
to gain insight into the origin of the far-IR localized and delocalized
motions present in peptides and where they can be found in the electromagnetic
spectrum.
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Affiliation(s)
- Sjors Bakels
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7-c, 6525 ED Nijmegen, The Netherlands
| | - Marie-Pierre Gaigeot
- LAMBE CNRS UMR8587, Université d'Evry val d'Essonne, Blvd F. Mitterrand, Bât Maupertuis, 91025 Evry, France
| | - Anouk M Rijs
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7-c, 6525 ED Nijmegen, The Netherlands
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20
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Karmakar S, Keshavamurthy S. Intramolecular vibrational energy redistribution and the quantum ergodicity transition: a phase space perspective. Phys Chem Chem Phys 2020; 22:11139-11173. [DOI: 10.1039/d0cp01413c] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The onset of facile intramolecular vibrational energy flow can be related to features in the connected network of anharmonic resonances in the classical phase space.
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Affiliation(s)
- Sourav Karmakar
- Department of Chemistry
- Indian Institute of Technology
- Kanpur
- India
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21
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Oswald S, Suhm MA. Soft experimental constraints for soft interactions: a spectroscopic benchmark data set for weak and strong hydrogen bonds. Phys Chem Chem Phys 2019; 21:18799-18810. [PMID: 31453998 DOI: 10.1039/c9cp03651b] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
An experimental benchmark data base on rotational constants, vibrational properties and energy differences for weakly and more strongly hydrogen-bonded complexes and their constituents from the spectroscopic literature is assembled. It is characterized in detail and finally contracted to a more compact, discriminatory set (ENCH-51, for Experimental Non-Covalent Harmonic with 51 entries). The meeting points between theory and experiment consist of equilibrium rotational constants and harmonic frequencies and energies, which are back-corrected from experimental observables and are very easily accessible by quantum chemical calculations. The relative performance of B3LYP-D3, PBE0-D3 and M06-2X density functional theory predictions with a quadruple-zeta basis set is used to illustrate systematic errors, error compensation and selective performance for structural, vibrational and energetical observables. The current focus is on perspectives and different benchmarking methodologies, rather than on a specific theoretical method or a specific class of compounds. Extension of the data base in chemical, observable and quantum chemical method space is encouraged.
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Affiliation(s)
- Sönke Oswald
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
| | - Martin A Suhm
- Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, 37077 Göttingen, Germany.
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