Communication: Vibrationally resolved photoelectron spectroscopy of the tetracyanoquinodimethane (TCNQ) anion and accurate determination of the electron affinity of TCNQ
- Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)
Tetracyanoquinodimethane (TCNQ) is widely used as an electron acceptor to form highly conducting organic charge-transfer solids. Surprisingly, the electron affinity (EA) of TCNQ is not well known and has never been directly measured. Here, we report vibrationally resolved photoelectron spectroscopy (PES) of the TCNQ{sup −} anion produced using electrospray and cooled in a cryogenic ion trap. Photoelectron spectrum taken at 354.7 nm represents the detachment transition from the ground state of TCNQ{sup −} to that of neutral TCNQ with a short vibrational progression. The EA of TCNQ is measured accurately to be 3.383 ± 0.001 eV (27 289 ± 8 cm{sup −1}), compared to the 2.8 ± 0.1 eV value known in the literature and measured previously using collisional ionization technique. In addition, six vibrational peaks are observed in the photoelectron spectrum, yielding vibrational frequencies for three totally symmetric modes of TCNQ. Two-photon PES via a bound electronic excited state of TCNQ{sup −} at 3.100 eV yields a broad low kinetic energy peak due to fast internal conversion to vibrationally excited levels of the anion ground electronic state. The high EA measured for TCNQ underlies its ability as a good electron acceptor.
- OSTI ID:
- 22493299
- Journal Information:
- Journal of Chemical Physics, Vol. 143, Issue 22; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AFFINITY
ANIONS
BINDING ENERGY
COMPARATIVE EVALUATIONS
ELECTRIC CONDUCTIVITY
ELECTRONS
EV RANGE
EXCITED STATES
GROUND STATES
INTERNAL CONVERSION
KINETIC ENERGY
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
PHOTONS
SOLIDS
TRAPS
VALENCE