Heterogeneously substituted radicals and carbenes: Photoelectron imaging of the FC(H)CN- and FCCN- anions

Andrew R. Dixon, Dmitry Khuseynov, Andrei Sanov

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Abstract

This work represents the next step in the studies of heterogeneous substitution effects in cyanohalo radicals and carbenes. Negative-ion photoelectron imaging was used to investigate the substituted radical and carbene derivatives of fluoroacetonitrile. We report a closed-shell singlet ground state for cyanofluorocarbene, FCCN, with a directly measured adiabatic electron affinity EA = 2.081 ± 0.002 eV and a singlet-triplet gap of ΔES-T = 0.42 ± 0.04 eV, estimated through a combination of experimental and theoretical results. The open-shell singlet 1A state was also observed experimentally. The cyanofluoromethyl radical, FC(H)CN, was similarly estimated to have an EA of 1.53 ± 0.08 eV. This value was used to estimate the C-H bond dissociation energy (BDE) of fluoroacetonitrile, DH298 = 90.7 ± 2.8 kcal mol-1. The results are discussed in comparison with results for other fluoro- and cyano-substituted radicals and carbenes, and in light of our recent work on the radical and carbene derivatives of chloroacetonitrile. The estimated ΔES-T of FCCN agrees well with the general trend of similar carbenes. We also find that, similar to chloroacetonitrile, the low C-H BDE of fluoroaceotnitrile indicates a synergistic stabilization of the corresponding radical by a π donor (halogen) and π acceptor (CN).

Original languageEnglish (US)
Pages (from-to)8533-8541
Number of pages9
JournalJournal of Physical Chemistry A
Volume118
Issue number37
DOIs
StatePublished - Sep 18 2014

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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