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Williams AE, Hammer NI, Tschumper GS. Relative energetics of CH 3CH 2O, CH 3CHOH, and CH 2CH 2OH radical products from ethanol dehydrogenation. J Chem Phys 2021; 155:114306. [PMID: 34551536 DOI: 10.1063/5.0062809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
This study has examined the relative energetics of nine stationary points associated with the three different radical isomers generated by removing a H atom from ethanol at the O atom (ethoxy, CH3CH2O), the α C atom (CH3CHOH), and the β C atom (CH2CH2OH). For the first time, CCSD(T) geometry optimizations and harmonic vibrational frequency computations with the cc-pVTZ and aug-cc-pVTZ basis sets have been carried out to characterize two unique minima for each isomer along with three transition state structures with Cs symmetry. Explicitly correlated CCSD(T) computations were also performed to estimate the relative energetics of these nine stationary points near the complete basis set limit. These benchmark results were used to assess the performance of various density functional theory (DFT) and wave function theory methods, and they will help guide method selection for future studies of alcohols and their radicals. The structures generated by abstracting H from the α C atom have significantly lower electronic energies (by at least 7 kcal mol-1) than the CH3CH2O and CH2CH2OH radicals. Although previously reported as a minimum on the ground-state surface, the 2A″ Cs structure of the ethoxy radical was found to be a transition state in this study with MP2, CCSD(T), and a number of DFT methods. An implicit solvation model used in conjunction with DFT and MP2 methods did not qualitatively change the relative energies of the isomers, but the results suggest that the local minima for the CH3CHOH and CH2CH2OH radicals could become more energetically competitive in condensed phase environments, such as liquid water and ethanol.
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Affiliation(s)
- Ashley E Williams
- Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi 38677, USA
| | - Nathan I Hammer
- Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi 38677, USA
| | - Gregory S Tschumper
- Department of Chemistry and Biochemistry, University of Mississippi, P.O. Box 1848, University, Mississippi 38677, USA
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Benitez Y, Parsons AJ, Lunny KG, Continetti RE. Dissociative Photodetachment Dynamics of the OH -(C 2H 4) Anion Complex. J Phys Chem A 2021; 125:4540-4547. [PMID: 34030440 DOI: 10.1021/acs.jpca.1c01835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photoelectron-photofragment coincidence (PPC) measurements on OH-(C2H4) anions at a photon energy of 3.20 eV revealed stable and dissociative photodetachment product channels, OH-C2H4 + e- and OH + C2H4 + e-, respectively. The main product channel observed was dissociation to the reactants (>67%), OH + C2H4 (v = 0, 1, 2) + e-, where vibrational excitation in the C-H stretching modes of the C2H4 photofragments corresponds to a minor channel. The low kinetic energy release (KER) of the dissociating fragments is consistent with weak repulsion between the OH + C2H4 reactants near the transition state as well as the partitioning of energy into rotation of the dissociation products. An impulsive model was used to account for rotational energy partitioning in the dissociative photodetachment (DPD) process and showed good agreement with the experimental results. The low KER of the dissociating fragments and the similarities in the photoelectron spectra between stable and dissociative events support a mechanism involving the van der Waals complex formed upon photodetachment of OH-(C2H4) as an intermediate in the dominant OH + C2H4 + e- dissociative channel.
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Affiliation(s)
- Yanice Benitez
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Austin J Parsons
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Katharine G Lunny
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Robert E Continetti
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
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Ye C, Gray V, Kushwaha K, Kumar Singh S, Erhart P, Börjesson K. Optimizing photon upconversion by decoupling excimer formation and triplet triplet annihilation. Phys Chem Chem Phys 2020; 22:1715-1720. [PMID: 31895392 DOI: 10.1039/c9cp06561j] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Perylene is a promising annihilator candidate for triplet-triplet annihilation photon upconversion, which has been successfully used in solar cells and in photocatalysis. Perylene can, however, form excimers, reducing the energy conversion efficiency and hindering further development of TTA-UC systems. Alkyl substitution of perylene can suppress excimer formation, but decelerate triplet energy transfer and triplet-triplet annihilation at the same time. Our results show that mono-substitution with small alkyl groups selectively blocks excimer formation without severly compromising the TTA-UC efficiency. The experimental results are complemented by DFT calculations, which demonstrate that excimer formation is suppressed by steric repulsion. The results demonstrate how the chemical structure can be modified to block unwanted intermolecular excited state relaxation pathways with minimal effect on the preferred ones.
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Affiliation(s)
- Chen Ye
- Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
| | - Victor Gray
- Department of Chemistry-Ångström Laboratory, Uppsala University, 75120, Uppsala, Sweden and Department of Physics, Cavendish Laboratory, University of Cambridge, 19 JJ Thompson Avenue, Cambridge, CB3 0HE, UK
| | - Khushbu Kushwaha
- Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
| | - Sandeep Kumar Singh
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Paul Erhart
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden
| | - Karl Börjesson
- Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg, Sweden.
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Womack CC, Ratliff BJ, Butler LJ, Lee SH, Lin JJM. Photoproduct Channels from BrCD2CD2OH at 193 nm and the HDO + Vinyl Products from the CD2CD2OH Radical Intermediate. J Phys Chem A 2012; 116:6394-407. [DOI: 10.1021/jp212167t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Caroline C. Womack
- The James Franck Institute and
the Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Britni J. Ratliff
- The James Franck Institute and
the Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Laurie J. Butler
- The James Franck Institute and
the Department of Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Shih-Huang Lee
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan, Republic
of China
| | - Jim Jr-Min Lin
- Institute of Atomic
and Molecular
Sciences, Academia Sinica, Taipei 10617,
Taiwan, Republic of China
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Edwards L, Ryazanov M, Reisler H, Klippenstein SJ. D-Atom Products in Predissociation of CD2CD2OH from the 202−215 nm Photodissociation of 2-Bromoethanol. J Phys Chem A 2010; 114:5453-61. [DOI: 10.1021/jp100203v] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- L.W. Edwards
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
| | - M. Ryazanov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
| | - H. Reisler
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA
| | - S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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