Photochemistry of fumaronitrile radical anion and its clusters

Dmitry Khuseynov, Andrew R. Dixon, Daniel J. Dokuchitz, Andrei M Sanov

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The photodetachment and photochemistry of the radical anion of fumaronitrile (trans-1,2-dicyanoethylene) and its clusters are investigated using photoelectron imaging and photofragment spectroscopy. We report the first direct spectroscopic determination of the adiabatic electron affinity (EA) of fumaronitrile (fn) in the gas phase, EA = 1.21 ± 0.02 eV. This is significantly smaller than one-half the EA of tetracyanoethylene (TCNE). The singlet-triplet splitting in fumaronitrile is determined to be δE S-T ≤ 2.6 eV, consistent with the known properties. An autodetachment transition is observed at 392 and 355 nm and assigned to the 2Bu anionic resonance in the vicinity of 3.3 eV. The results are in good agreement with the predictions of the CCSD(T) and EOM-XX-CCSD(dT) (XX = IP, EE) calculations. The H2O and Ar solvation energies of fn- are found to be similar to the corresponding values for the anion of TCNE. In contrast, a very large (0.94 eV) photodetachment band shift, relative to fn-, is observed for (fn)2-. In addition, while the photofragmentation of fn-, fn -·Ar, and fn-(H2O)1,2 yielded only the CN- fragment ions, the dominant anionic photofragment of (fn)2- is the fn- monomer anion. The band shift, exceeding the combined effect of two water molecules, and the fragmentation pattern, inconsistent with an intact fn- chromophore, rule out an electrostatically solvated fn-·fn structure of (fn)2- and favor a covalently bound dimer anion. A C 2 symmetry (fn)2- structure, involving a covalent bond between the two fn moieties, is proposed.

Original languageEnglish (US)
Pages (from-to)4510-4518
Number of pages9
JournalJournal of Physical Chemistry A
Volume118
Issue number25
DOIs
StatePublished - Jun 26 2014

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Photochemical reactions
photochemical reactions
Anions
electron affinity
anions
photodetachment
shift
covalent bonds
chromophores
solvation
Electron affinity
fragmentation
photoelectrons
monomers
dimers
fragments
vapor phases
fumaronitrile
symmetry
predictions

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Photochemistry of fumaronitrile radical anion and its clusters. / Khuseynov, Dmitry; Dixon, Andrew R.; Dokuchitz, Daniel J.; Sanov, Andrei M.

In: Journal of Physical Chemistry A, Vol. 118, No. 25, 26.06.2014, p. 4510-4518.

Research output: Contribution to journalArticle

Khuseynov, Dmitry ; Dixon, Andrew R. ; Dokuchitz, Daniel J. ; Sanov, Andrei M. / Photochemistry of fumaronitrile radical anion and its clusters. In: Journal of Physical Chemistry A. 2014 ; Vol. 118, No. 25. pp. 4510-4518.
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AB - The photodetachment and photochemistry of the radical anion of fumaronitrile (trans-1,2-dicyanoethylene) and its clusters are investigated using photoelectron imaging and photofragment spectroscopy. We report the first direct spectroscopic determination of the adiabatic electron affinity (EA) of fumaronitrile (fn) in the gas phase, EA = 1.21 ± 0.02 eV. This is significantly smaller than one-half the EA of tetracyanoethylene (TCNE). The singlet-triplet splitting in fumaronitrile is determined to be δE S-T ≤ 2.6 eV, consistent with the known properties. An autodetachment transition is observed at 392 and 355 nm and assigned to the 2Bu anionic resonance in the vicinity of 3.3 eV. The results are in good agreement with the predictions of the CCSD(T) and EOM-XX-CCSD(dT) (XX = IP, EE) calculations. The H2O and Ar solvation energies of fn- are found to be similar to the corresponding values for the anion of TCNE. In contrast, a very large (0.94 eV) photodetachment band shift, relative to fn-, is observed for (fn)2-. In addition, while the photofragmentation of fn-, fn -·Ar, and fn-(H2O)1,2 yielded only the CN- fragment ions, the dominant anionic photofragment of (fn)2- is the fn- monomer anion. The band shift, exceeding the combined effect of two water molecules, and the fragmentation pattern, inconsistent with an intact fn- chromophore, rule out an electrostatically solvated fn-·fn structure of (fn)2- and favor a covalently bound dimer anion. A C 2 symmetry (fn)2- structure, involving a covalent bond between the two fn moieties, is proposed.

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