Cyclic Perfluorocarbon Radicals and Anions Having High Global Warming Potentials (GWPs):  Structures, Electron Affinities, and Vibrational Frequencies

• Published in: Journal of the American Chemical Society 2004-06, Vol.126 (21), p.6692-6702
• Main Authors: Bera, Partha Pratim, Horný, Ľuboš, Schaefer, Henry F
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Ionization potentials, electron affinities, molecular core binding energy; Molecular properties and interactions with photons; Molecular spectra; Physics; Properties of molecules and molecular ions; Vibrational analysis
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0305297

Adiabatic electron affinities, optimized molecular geometries, and IR-active vibrational frequencies have been predicted for small cyclic hydrocarbon radicals C n H2 n - 1 (n = 3−6) and their perfluoro counterparts C n F2 n - 1 (n = 3−6). Total energies and optimized geometries of the radicals and corresponding anions have been obtained using carefully calibrated (Chem. Rev. 2002, 102, 231) density functional methods, namely, the B3LYP, BLYP, and BP86 functionals in conjunction with the DZP++ basis set. The predicted electron affinities show that only the cyclopropyl radical tends to bind electrons among the hydrocarbon radicals studied. The trend for the perfluorocarbon (PFC) radicals is quite different. The electron affinities increase with expanding ring size until n = 5 and then slightly decrease at n = 6. Predicted electron affinities of the hydrocarbon radicals using the B3LYP hybrid functional are 0.24 eV (C3H5/C3H5 -), −0.19 eV (C4H7/C4H7 -), −0.15 eV (C5H9/C5H9 -), and −0.11 eV (C6H11/C6H11 -). Analogous electron affinities of the perflurocarbon radicals are 2.81 eV (C3F5/C3F5 -), 3.18 eV (C4F7/C4F7 -), 3.34 eV (C5F9/C5F9 -), and 3.21 eV (C6F11/C6F11 -).