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Modelling of the torsional ir spectra of the HSSSH, DSSSH, and DSSSD molecules. COMPUT THEOR CHEM 2023. [DOI: 10.1016/j.comptc.2023.114080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
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Medel R. Simple models for the quick estimation of ground state hydrogen tunneling splittings in alcohols and other compounds. Phys Chem Chem Phys 2021; 23:17591-17605. [PMID: 34369526 DOI: 10.1039/d1cp02115j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Models for the quick estimation of energy splittings caused by coherent tunneling of hydrogen atoms are evaluated with available experimental data for alcohols and improvements are proposed. The discussed models are mathematically simple and require only results from routine quantum chemical computations, i.e. hybrid DFT calculation of the equilibrium geometry and the transition state within the harmonic approximation. A benchmark of experimental splittings spanning four orders of magnitude for 27 alcohol species is captured by three evaluated models with a mean symmetric deviation factor of 1.7, 1.5 and 1.4, respectively, i.e. the calculated values deviate on average by this factor in either direction. Limitations of the models are explored with alcohols featuring uncommon properties, such as an inverted conformational energy sequence, a very light molecular frame, an elevated torsional frequency, or a coupling with a second internal degree of freedom. If the splitting of either the protiated or deuterated form of an alcohol is already experimentally determined, the one of the second isotopolog can be estimated by three additional models with a mean symmetric deviation factor of 1.14, 1.19 and 1.15, respectively. It is shown that this can be achieved with a novel approach without any quantum chemical calculation by directly correlating experimental splittings of isotopologs across related species. This is also demonstrated for other classes of compounds with hydrogen tunneling, such as amines, thiols, and phenols. Furthermore, it is found that the isotope effect can even be anticipated without any further knowledge about the system solely from the size of either splitting with a mean symmetric deviation factor of 1.3. This is based on an extensive sample of 77 pairs of splittings spanning eight orders of magnitude for isotopologs of chemically diverse compounds.
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Affiliation(s)
- Robert Medel
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
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Medel R, Suhm MA. Understanding benzyl alcohol aggregation by chiral modification: the pairing step. Phys Chem Chem Phys 2020; 22:25538-25551. [PMID: 33169124 DOI: 10.1039/d0cp04825a] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combination of linear infrared and Raman spectroscopy in supersonic slit jet expansions is used to clarify the conformational preferences in the dimer of the transiently chiral benzyl alcohol (phenylmethanol) under vacuum isolation. By experimentally exploring close analogies with the permanently chiral 1-phenylethanol, which is conformationally locked in the jet through intramolecular chirality induction, and by computational analysis of their conformational energy landscapes, several conclusions are drawn. The lowest energy dimer is confirmed to be cooperatively OHOHπ-bonded and shown to be homochiral. Its heterochiral counterpart is slightly higher in energy and can be spectrally assigned as a minor constituent. A metastable heterochiral OHπ/OHπ structure with weakly coupled hydrogen bonds is efficiently trapped behind a Ci symmetry-enhanced barrier and can be assigned by IR/Raman mutual exclusion. Its homochiral counterpart is kinetically less stable but might be addressed by rotational spectroscopy. Ratings of standard density functionals with a standard basis set in terms of reproducing these experimental chirality synchronization benchmarks are presented.
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Affiliation(s)
- Robert Medel
- Institute of Physical Chemistry, University of Goettingen, Tammannstr. 6, 37077 Goettingen, Germany.
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Ivanova B, Spiteller M. 3D structural analysis of isomers of benzaldehydes and benzoic acids and their base catalysed C–C coupled derivatives under electrospray ionization conditions – mass spectrometric stochastic dynamic and quantum chemical approaches. J Mol Struct 2020. [DOI: 10.1016/j.molstruc.2019.127022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Evangelisti L, Caminati W. Modeling the internal rotation tunnelling in benzyl alcohol by ring fluorination: The rotational spectrum of 3,5-difluorobenzyl alcohol. Chem Phys Lett 2019. [DOI: 10.1016/j.cpletx.2018.100004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Ivanova B, Spiteller M. Experimental and theoretical mass spectrometric quantification of diffusion parameters and 3D structural determination of ions of L-tryptophyl-l-tryptophan in electrospray ionization conditions in positive operation mode. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2018.07.055] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Quantitative correlations between collision induced dissociation mass spectrometry coupled with electrospray ionization or atmospheric pressure chemical ionization mass spectrometry – Experiment and theory. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2017.12.098] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Ivanova B, Spiteller M. Quantitative collision induced mass spectrometry of substituted piperazines – A correlative analysis between theory and experiment. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2017.07.107] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Simón-Carballido L, Bao JL, Alves TV, Meana-Pañeda R, Truhlar DG, Fernández-Ramos A. Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods. J Chem Theory Comput 2017; 13:3478-3492. [PMID: 28665605 DOI: 10.1021/acs.jctc.7b00451] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational-vibrational partition functions. Twenty molecules having two hindered rotors were studied for temperatures between 100 and 2500 K. These molecules present several kinds of situations; they include molecules with nearly separable rotors, molecules in which the reduced moments of inertia change substantially with the internal rotation, and molecules presenting compound rotation. Partition functions obtained by the rigid-rotor harmonic oscillator approximation, a method involving global separability of torsions and the multistructural methods without explicit potential coupling [MS-T(U)] and with explicit potential coupling [MS-T(C)] of torsions, are compared to those obtained with a quantized version - called the extended two-dimensional torsion (E2DT) method - of the extended hindered rotor approximation of Vansteenkiste et al. ( Vansteenkiste et al. J. Chem. Phys. 2006 , 124 , 044314 ). In the E2DT method, quantum effects due to the torsional modes were incorporated by the two-dimensional nonseparable method, which is a method that is based on the solution of the torsional Schrödinger equation and that includes full coupling in both the kinetic and potential energy. By comparing other methods to the E2DT method and to experimental thermochemical data, this study concludes that the harmonic approximation yields very poor results at high temperatures; the global separation of torsions from the rest of the degrees of freedom is not justified even when an accurate method to treat the torsions is employed; it is confirmed that methods based on less complete potential energy coupling of torsions, such as MS-T(U), are not accurate when dealing with rotors with different barrier heights, and more complete inclusion of torsional coupling to the method in MS-T(C) improves substantially the results in such a way that it could be used in cases where the E2DT method is unaffordable.
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Affiliation(s)
- Luis Simón-Carballido
- Center for Research in Biological Chemistry and Molecular Materials (CIQUS) and Department of Physical Chemistry, University of Santiago de Compostela , 15782 Santiago de Compostela, Spain
| | - Junwei Lucas Bao
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States
| | - Tiago Vinicius Alves
- Departamento de Físico-Química, Instituto de Química, Universidade Federal da Bahia , Rua Barão de Jeremoabo, 147, Salvador, Bahia 40170-115, Brazil
| | - Rubén Meana-Pañeda
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States.,Laboratory of Computational Biology, NHLBI, National Institutes of Health, 5635 Fishers Lane, Suite T-906, Rockville, Maryland 20852, United States
| | - Donald G Truhlar
- Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431, United States
| | - Antonio Fernández-Ramos
- Center for Research in Biological Chemistry and Molecular Materials (CIQUS) and Department of Physical Chemistry, University of Santiago de Compostela , 15782 Santiago de Compostela, Spain
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