Revealing Long-Range Substituent Effects in the Laser-Induced Fluorescence and Dispersed Fluorescence Spectra of Jet-Cooled CHxF3- xCH2O (x = 1, 2, 3) Radicals

Benedek Koncz; Gábor Bazsó; Md Asmaul Reza; Hamzeh Telfah; Kristóf Hegedüs; Jinjun Liu; György Tarczay

doi:10.1021/acs.jpca.9b09829

Revealing Long-Range Substituent Effects in the Laser-Induced Fluorescence and Dispersed Fluorescence Spectra of Jet-Cooled CH_xF_{3- x}CH₂O (x = 1, 2, 3) Radicals

J Phys Chem A. 2019 Dec 26;123(51):10947-10960. doi: 10.1021/acs.jpca.9b09829. Epub 2019 Dec 16.

Authors

Benedek Koncz¹, Gábor Bazsó¹, Md Asmaul Reza², Hamzeh Telfah², Kristóf Hegedüs³, Jinjun Liu^{2

4}, György Tarczay^{1

5}

Affiliations

¹ ELTE Eötvös University , Institute of Chemistry, Laboratory of Molecular Spectroscopy , PO Box 32, H-1518 Budapest 112 , Hungary.
² Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States.
³ Research Centre for Natural Sciences , Institute of Organic Chemistry , PO Box 286, H-1519 Budapest , Hungary.
⁴ Conn Center for Renewable Energy Research , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States.
⁵ MTA-ELTE Lendület Laboratory Astrochemistry Research Group , PO Box 32, H-1518 Budapest 112 , Hungary.

PMID: 31790245
DOI: 10.1021/acs.jpca.9b09829

Abstract

The B̃-X̃ laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the atmospherically important β-monofluoro ethoxy (MFEO), β,β-difluoro ethoxy (DFEO), and β,β,β-trifluoro ethoxy (TFEO) radicals were recorded with vibronic resolution under jet-cooled conditions. To simulate the spectra, Franck-Condon factors were obtained from quantum chemical computations carried out at the CAM-B3LYP/6-311++G(d,p) level of theory. The simulations reproduce well both the LIF and DF spectra. Both conformers (G and T) of MFEO and one (G) of the two conformers of DFEO contribute to the LIF spectrum. A comparison between the experimental and calculated spectra confirms the expected long-range field effects of the CH_xF_3-x group on electronic transition energies and bond strengths, especially in the excited electronic (B̃) state. Although TFEO has only one conformer, its LIF spectrum is highly congested, which is attributed to the interaction between CO stretch and the -CF₃ internal rotation.