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Nagasawa H, Ogawa S, Kashihara W, Isozaki T, Hirata K, Ishiuchi SI, Fujii M, Suzuki T. Conformational preference of 2-(4-methoxyphenyl)ethanol studied by supersonic jet spectroscopy: Intramolecular OH/π interaction. J Chem Phys 2024; 160:024303. [PMID: 38189621 DOI: 10.1063/5.0184664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Accepted: 12/20/2023] [Indexed: 01/09/2024] Open
Abstract
A π-type hydrogen bonding between the OH group and the π electron is a crucial factor for the conformational preference of the molecular structure with a flexible group. However, the information on the effect of the substituent on the OH/π interaction is insufficient. The laser-induced fluorescence (LIF) excitation, the dispersed fluorescence (DF), the IR-UV hole-burning, and the IR dip spectra of jet-cooled 2-(4-methoxyphenyl)ethanol were measured for the first time. Almost all bands observed in the spectral region of 35 550-36 500 cm-1 in the LIF excitation spectrum were successfully assigned with the DF and the IR-UV hole-burning spectra coupled with the quantum chemical calculation at M06-2x/6-311G and MP2/6-311G levels. Five conformers were found in the LIF excitation spectrum. The most stable conformer was Ggπ, and the second most stable conformer was Ggπ' (the trans rotamer of the methoxy group for Ggπ). Ggπ and Ggπ' had the OH group directed toward the π electron system of the benzene ring. The OH stretching frequency of Ggπ/Ggπ' of MPE in the IR dip spectra was red-shifted against that of Ggπ of phenylethanol, indicating that the introduction of the methoxy group would enhance the intramolecular OH/π interaction. In addition, the torsional vibration between the benzene ring and the side chain (-CH2CH2OH) (mode 63) was observed in the DF spectra of the Ggπ-00 and Ggπ'-00 band excitation, but their intensities were rather different, resulting from the different orientation of the OH group for each conformer toward the π electron system. The methoxy group would increase the negative charge on the benzene ring and would enhance the intramolecular OH/π interaction through the electrostatic interaction.
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Affiliation(s)
- Hironari Nagasawa
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan
| | - Sakuya Ogawa
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan
| | - Wataru Kashihara
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan
| | - Tasuku Isozaki
- Division of Natural Sciences, College of Arts and Sciences, J. F. Oberlin University, 3758 Tokiwa-machi, Machida, Tokyo 194-0294, Japan
| | - Keisuke Hirata
- Laboratory for Chemistry and Life Science, Institute for Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Shun-Ichi Ishiuchi
- Laboratory for Chemistry and Life Science, Institute for Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
- Department of Chemistry, School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Masaaki Fujii
- Laboratory for Chemistry and Life Science, Institute for Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
| | - Tadashi Suzuki
- Department of Chemistry and Biological Science, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan
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Kato T, Fujii A. Experimental confirmation of the Badger-Bauer rule in the protonated methanol clusters: weak hydrogen bond formation as a measure of terminal OH acidity in hydrogen bond networks. Phys Chem Chem Phys 2023; 25:30188-30192. [PMID: 37920966 DOI: 10.1039/d3cp04644c] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
We report a linear correlation between the OH stretch frequency shift of the protonated methanol cluster, H+(MeOH)n, upon the π-hydrogen bond formation with benzene and the enthalpy change in clustering of H+(MeOH)n to H+(MeOH)n+1. This result suggests a new method to explore hydrogen bond strength in hydrogen bond networks.
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Affiliation(s)
- Takeru Kato
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Asuka Fujii
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
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Shinkai T, Hsu PJ, Fujii A, Kuo JL. Infrared spectroscopy and theoretical structure analyses of protonated fluoroalcohol clusters: the impact of fluorination on the hydrogen bond networks. Phys Chem Chem Phys 2022; 24:12631-12644. [PMID: 35579401 DOI: 10.1039/d2cp01300b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
To explore the impact of fluorination on the hydrogen bond networks of protonated alkylalcohols, infrared spectroscopy and theoretical computations of protonated 2,2,2-trifluoroethanol clusters, H+(TFE)n, (n = 4-7), were performed. It has been demonstrated that the development of the hydrogen bond networks from a linear type to cyclic types occurs in this size region for the protonated alkylalcohol clusters. In contrast, infrared spectroscopy of H+(TFE)n in the OH/CH stretch region clearly indicated that the linear type structures are held in the whole size range, irrespective of temperature of the clusters. The extensive stable isomer structure search of H+(TFE)n based on our latest sampling approach supported the strong preference of the linear type hydrogen bond networks. Detailed analyses of the free OH stretching vibrational bands evidenced the intra- and intermolecular OH⋯FC interactions in the clusters. In addition, infrared spectra of protonated clusters of 2,2-difluoroethanol, 2,2-difluoropropanol, and 3,3,3-trifluoropropanol were measured for n = 4 and 5, and their spectra also indicated the effective inhibition of the cyclic hydrogen bond network formation by the fluorination.
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Affiliation(s)
- Takahiro Shinkai
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Po-Jen Hsu
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
| | - Asuka Fujii
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
| | - Jer-Lai Kuo
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan.
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