title: Resolving an apparent discrepancy between theory and experiment: spin-spin coupling constants for FCCF.
abstract: Ab initio equation of motion coupled cluster singles and doubles (EOM-CCSD) and second-order polarization propagator approximation (SOPPA) calculations have been performed to evaluate spin-spin coupling constants for FCCF (difluoroethyne). The computed EOM-CCSD value of (3)J(F-F) obtained at the experimental geometry of this molecule supports the previously reported experimental value of 2.1 Hz, thereby resolving an apparent discrepancy between theory and experiment. This coupling constant exhibits a strong dependence on the C-C and C-F distances, and its small positive value results from a sensitive balance of paramagnetic spin-orbit (PSO) and spin-dipole (SD) terms. The three other unique FCCF coupling constants (1)J(C-C), (1)J(C-F), and (2)J(C-F) have also been reported and compared with experimental data. While (1)J(C-F) is in agreement with experiment, the computed value of (2)J(C-F) is larger than our estimate of the experimental coupling constant.
authors.affiliation: Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA. jedelbene@ysu.edu
authors.forename: Janet E
authors.initials: JE
authors.lastname: Del Bene
authors.forename: Patricio F
authors.initials: PF
authors.lastname: Provasi
authors.forename: Ibon
authors.initials: I
authors.lastname: Alkorta
authors.forename: José
authors.initials: J
authors.lastname: Elguero
mesh_terms: D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics
chemical_list: D006845:Hydrocarbons, Fluorinated; C533928:difluoroethyne