Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces
Abstract
The single-conformation ultraviolet and infrared spectroscopy of three short-chain para-dialkylbenzenes (para-diethylbenzene, para-dipropylbenzene, and para-dibutylbenzene) is reported for the jet-cooled, isolated molecules. The present study builds off previous work on single-chain n-alkylbenzenes, where an anharmonic local mode Hamiltonian method was developed to account for stretch-bend Fermi resonance in the alkyl CH stretch region [D. P. Tabor et al., J. Chem. Phys. 144, 224310 (2016)]. The jet-cooled molecules are interrogated using laser-induced fluorescence (LIF) excitation, fluorescence dip infrared spectroscopy, and dispersed fluorescence. The LIF spectra in the S1 ← S0 origin region show a dramatic increase in the number of resolved transitions with increasing length of the alkyl chains, reflecting an explosion in the number of unique low-energy conformations formed when two independent alkyl chains are present. Since the barriers to isomerization of the alkyl chain are similar in size, this results in an “egg carton” shaped potential energy surface. A combination of electronic frequency shift and alkyl CH stretch infrared spectra is used to generate a consistent set of conformational assignments. Using these experimental techniques in conjunction with computational methods, subsets of origin transitions in the LIF excitation spectrum can be classified into different conformational families. Two conformations are resolved inmore »
- Authors:
-
- Purdue Univ., West Lafayette, IN (United States)
- Publication Date:
- Research Org.:
- Purdue Univ., West Lafayette, IN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1512948
- Alternate Identifier(s):
- OSTI ID: 1436560
- Grant/Contract Number:
- FG02-96ER14656
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Journal of Chemical Physics
- Additional Journal Information:
- Journal Volume: 148; Journal Issue: 18; Journal ID: ISSN 0021-9606
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Citation Formats
Mishra, Piyush, Hewett, Daniel M., and Zwier, Timothy S. Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces. United States: N. p., 2018.
Web. doi:10.1063/1.5029373.
Mishra, Piyush, Hewett, Daniel M., & Zwier, Timothy S. Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces. United States. https://doi.org/10.1063/1.5029373
Mishra, Piyush, Hewett, Daniel M., and Zwier, Timothy S. Wed .
"Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces". United States. https://doi.org/10.1063/1.5029373. https://www.osti.gov/servlets/purl/1512948.
@article{osti_1512948,
title = {Conformational explosion: Understanding the complexity of short chain para -dialkylbenzene potential energy surfaces},
author = {Mishra, Piyush and Hewett, Daniel M. and Zwier, Timothy S.},
abstractNote = {The single-conformation ultraviolet and infrared spectroscopy of three short-chain para-dialkylbenzenes (para-diethylbenzene, para-dipropylbenzene, and para-dibutylbenzene) is reported for the jet-cooled, isolated molecules. The present study builds off previous work on single-chain n-alkylbenzenes, where an anharmonic local mode Hamiltonian method was developed to account for stretch-bend Fermi resonance in the alkyl CH stretch region [D. P. Tabor et al., J. Chem. Phys. 144, 224310 (2016)]. The jet-cooled molecules are interrogated using laser-induced fluorescence (LIF) excitation, fluorescence dip infrared spectroscopy, and dispersed fluorescence. The LIF spectra in the S1 ← S0 origin region show a dramatic increase in the number of resolved transitions with increasing length of the alkyl chains, reflecting an explosion in the number of unique low-energy conformations formed when two independent alkyl chains are present. Since the barriers to isomerization of the alkyl chain are similar in size, this results in an “egg carton” shaped potential energy surface. A combination of electronic frequency shift and alkyl CH stretch infrared spectra is used to generate a consistent set of conformational assignments. Using these experimental techniques in conjunction with computational methods, subsets of origin transitions in the LIF excitation spectrum can be classified into different conformational families. Two conformations are resolved in para-diethylbenzene, seven in para-dipropylbenzene, and about nineteen in para-dibutylbenzene. These chains are largely independent of each other as there are no new single-chain conformations induced by the presence of a second chain. A cursory LIF excitation scan of para-dioctylbenzene shows a broad congested spectrum at frequencies consistent with interactions of alkyl chains with the phenyl π cloud},
doi = {10.1063/1.5029373},
journal = {Journal of Chemical Physics},
number = 18,
volume = 148,
place = {United States},
year = {Wed May 09 00:00:00 EDT 2018},
month = {Wed May 09 00:00:00 EDT 2018}
}
Web of Science
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Works referencing / citing this record:
Broadband rotational spectroscopy of trans 3-pentenenitrile and 4-pentenenitrile
journal, January 2019
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