Theoretical Investigations on Fluorine-Substituted Ethylene Dications C2HnF4-n2+(n = 0–4)

✍ Scribed by Gernot Frenking; Wolfram Koch; Helmut Schwarz

• Book ID: 102880677
• Publisher: John Wiley and Sons
• Year: 1986
• Tongue: English
• Weight: 837 KB
• Volume: 7
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540070404

✦ Synopsis

The optimized geometries and energies of fluorine-substituted ethylene dications C2H,F4-,'+ (n = 0-4) have been investigated by means of ab initio methods. At the MP3/6-31G**//6-31G* + zero-point energy level of theory, the results predict that C2F4'+ and C2HF3'+ are planar, while C2H4'+, C2H3F2+ and 1,l -CzH2Fz2+ prefer a perpendicular geometry. For 1,2 -C2H2F2" an energy difference of only 0.3 kcal/mol is found between the (trans) planar and perpendicular structure. The stabilizations attributed to hyperconjugation, fluorine lone-pair donation, and (C -F) double-bond conjugation are discussed.

A comparison is made for the C-C and C-F stretching frequencies determined at 6-31G*//6-31G* between the neutral and dicationic species. The theoretically determined ionization energies for the vertical process N+ + N2+ at the MP3/6-31G*//3-21G level are compared with experimental Qdn values.