Barrierless proton transfer across weak CH⋯O hydrogen bonds in dimethyl ether dimer
- Laboratory of Physical Chemistry, ETH Zürich, Zürich 8093 (Switzerland)
- Department of Chemistry, Boston University, Boston, Massachusetts 02215-2521 (United States)
- Molecular Dynamics Group, Paul Scherrer Institut, Villigen 5232 (Switzerland)
- Department of Chemistry, University of the Pacific, Stockton, California 95211 (United States)
We present a combined computational and threshold photoelectron photoion coincidence study of two isotopologues of dimethyl ether, (DME − h{sub 6}){sub n} and (DME − d{sub 6}){sub n}n = 1 and 2, in the 9–14 eV photon energy range. Multiple isomers of neutral dimethyl ether dimer were considered, all of which may be present, and exhibited varying C–H⋯O interactions. Results from electronic structure calculations predict that all of them undergo barrierless proton transfer upon photoionization to the ground electronic state of the cation. In fact, all neutral isomers were found to relax to the same radical cation structure. The lowest energy dissociative photoionization channel of the dimer leads to CH{sub 3}OHCH{sub 3}{sup +} by the loss of CH{sub 2}OCH{sub 3} with a 0 K appearance energy of 9.71 ± 0.03 eV and 9.73 ± 0.03 eV for (DME − h{sub 6}){sub 2} and deuterated (DME − d{sub 6}){sub 2}, respectively. The ground state threshold photoelectron spectrum band of the dimethyl ether dimer is broad and exhibits no vibrational structure. Dimerization results in a 350 meV decrease of the valence band appearance energy, a 140 meV decrease of the band maximum, thus an almost twofold increase in the ground state band width, compared with DME − d{sub 6} monomer.
- OSTI ID:
- 22415532
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 11 Vol. 142; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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