Anharmonic Aspects in Vibrational Circular Dichroism Spectra from 900 to 9000 cm-1 for Methyloxirane and Methylthiirane

Year: 2022

Authors: Fuse M., Longhi G., Mazzeo G., Stranges S., Leonel F., Aquila G., Bodo E., Brunetti B., Bicchi C., Cagliero C., Bloino J., Abbate S.

Autors Affiliation: Scuola Normale Super Pisa, I-56125 Pisa, Italy; Univ Brescia, Dipartimentodi Med Mol & Traslazionale, Brescia I-25123, Italy; CNR, Inst Nazl Ott INO, Res Unit Brescia, I-25123 Brescia, Italy; Univ Brescia, Dipartimento Med Mol & Traslazionale, I-25123 Brescia, Italy; Univ ´ La Sapienza, Dipartimentodi Chim Tecnol Farmaco, 00185, I-34149 Rome, Italy; OM CNR, Lab TASC, I-34149 Trieste, Italy; Univ ´ La Sapienza, Dipartimento Chim, I-00185 Rome, Italy; Univ Roma La Sapienza, ISMN CNR, I-00185 Rome, Italy; Univ Torino, Dipartimentodi Sci & Tecnol Farm, I-00124 Turin, Italy.

Abstract: Vibrational circular dichroism (VCD) spectra and the corresponding IR spectra of the chiral isomers of methyloxirane and of methylthiirane have been reinvestigated, both experimentally and theoretically, with particular attention to accounting for anharmonic corrections, as calculated by the GVPT2 approach. De novo recorded VCD spectra in the near IR (NIR) range regarding CH-stretching overtone transitions, together with the corresponding NIR absorption spectra, were also considered and accounted for, both with the GVPT2 and with the local mode approaches. Comparison of the two methods has permitted us to better describe the nature of active anharmonic modes in the two molecules and the role of mechanical and electrical anharmonicity in determining the intensities of VCD and IR/NIR data. Finally, two nonstandard IR/NIR regions have been investigated: the first one about approximate to 2000 cm(-1), involving mostly two-quanta bending mode transitions, the second one between 7000 and 7500 cm(-1) involving three-quanta transitions containing CH-stretching overtones and HCC/HCH bending modes.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY A

More Information: Funding was provided by the Italian Ministry of Education, University and Research (MIUR) through the PRIN program (PRIN 2017, project Physico-chemical Heuristic Approaches: Nanoscale Theory of Molecular Spectroscopy (PHAN-TOMS), prot. 2017A4XRCA and PRIN 2020, project Photoreactive Systems upon Irradiation: Modeling and Observation of Vibrational Interactions with the Environment (PSI-MOVIE), prot. 2020HTSXMA). S.S. and E.B. gratefully acknowledge financial support of La Sapienza, University of Rome through the project RG1181643265D950 Multi-disciplinary study of intrinsic properties of model chiral molecules. We thank JASCO Europe and Dr. Marco Grandi for help and assistance on our NIR-VCD apparatus. The SMART@SNS Laboratory (http://smart.sns.it) and the CINECA award under the ISCRA initiative are acknowledged for providing high-performance computing facilities.
KeyWords: Transition Current-density; Hcch Molecular Fragment; Raman Optical-activity; Overtone Transitions; Propylene-oxide; Local Modes; Vcd Spectra; Basis-sets; Nir-vcd; Water
DOI: 10.1021/acs.jpca.2c05332

Citations: 14
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