title: Bis(trifluoroaceto) disulfide (CF3C(O)OSSOC(O)CF3): a HeI photoelectron spectroscopy and theoretical study.
abstract: Bis(trifluoroaceto) disulfide CF(3)C(O)OSSOC(O)CF(3) was prepared and studied by Raman, photoelectron spectroscopy (PES), and theoretical calculations. This molecule exhibits gauche conformation with both C=O groups cis to the S-S bond; the structure of the OSSO moiety is characterized by dihedral angle delta(OSSO) = -95.1 degrees due to the sulfur-sulfur lone pair interactions. The contracted S-S bond (1.979 Angstroms) and relatively high rotational barrier (19.29 kcal mol(-1) at the B3LYP/6-31G level) of the delta(OSSO) indicate the partial resonance-induced double bond character in this molecule. After ionization, the ground cationic-radical form of CF(3)C(O)OSSOC(O)CF(3)(*+) adopts a trans planar main-atom structure (delta(OSSO) = 180 degrees and delta(OCOS) = 0 degrees ) with C(2)(h) symmetry. The S-S bond elongates to 2.054 Angstroms, while the S-O bond shortens from 1.755 Angstroms in neutral form to 1.684 Angstroms in its corresponding cationic-radical form. The adiabatic ionization energy of 9.91 eV was obtained accordingly. The first two HOMOs correspond to the electrons mainly localized on the sulfur 3p lone pair MOs: 3ppi {36a (n(A)(S))](-1) and 3ppi [35b (n(B)(S), n(B)(O(C)(=)(O)))](-1), with an experimental energy separation of 0.16 eV. The first vertical ionization energy is determined to be 10.81 eV.
authors.affiliation: State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Zeng
authors.forename: Maofa
authors.initials: M
authors.lastname: Ge
authors.forename: Zheng
authors.initials: Z
authors.lastname: Sun
authors.forename: Dianxun
authors.initials: D
authors.lastname: Wang
mesh_terms: D005466:Fluorocarbons / Q000138:chemical synthesis / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods; D013440:Sulfides / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D005466:Fluorocarbons; D013440:Sulfides; C522307:bis(trifluoroaceto) disulfide