Chem. J. Chinese Universities ›› 2022, Vol. 43 ›› Issue (6): 20220044.doi: 10.7503/cjcu20220044

• Physical Chemistry • Previous Articles     Next Articles

Theoretical Investigations on the Electronic Structures and Reactivity of Heptafluoro-iso-butyronitrile Anion

DAI Wei, HOU Hua, WANG Baoshan()   

  1. College of Chemistry and Molecular Sciences,Wuhan University,Wuhan 430072,China
  • Received:2022-01-18 Online:2022-06-10 Published:2022-03-04
  • Contact: WANG Baoshan E-mail:baoshan@whu.edu.cn
  • Supported by:
    the National Key Research and Development Program of China(2021YFB2401400);the National Natural Science Foundation of China(U1966211)

Abstract:

Heptafluoro-iso-butyronitrile(C4) has attracted considerable interest for its use as a novel eco-friendly dielectric gas in various high-voltage applications. Electronic structures, photoelectron spectra, lifetime, reaction mechanisms, and kinetics for the C4- anion formed by electron attachment to C4, together with the C4-+CO2 reaction, were calculated using various high-level ab initio methods. The electron in the π* anti-bond orbital of C≡N leads to the bent C—C=N geometry of C4- anion, and best theoretical adiabatic electron affinity is 0.30 eV. Photodetachment spectrum of C4- anion exhibits significant absorption in the range 0—2 eV peaked at 1.63 eV. C4- anion prefers to decompose via C—F bond fission, surmounting a barrier of ca. 9 kJ/mol, to form the long-lived [F...(CF32CCN]- intermediate, in which the C...F distance is as long as around 0.2 nm. The C4-+CO2 reaction takes place via three stepwise association/elimination mechanisms, namely, F, C or N of CN site-specified attacking by CO2, resulting in energetically feasible electron-transfer from CN to CO2. The present theoretical results shed new light on the high dielectric strength of C4 and the synergistic effect of the C4/CO2 gas mixture.

Key words: Heptafluoro-iso-butyronitrile anion, Electron affinity, Electron attachment, Ion-molecule reaction, Synergistic effect

CLC Number: 

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