Resolving an apparent discrepancy between theory and experiment: spin-spin coupling constants for FCCF.
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.
Del Bene
Janet E
JE
Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA. jedelbene@ysu.edu
Provasi
Patricio F
PF
Alkorta
Ibon
I
Elguero
José
J
D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008280:Magnetics
D006845:Hydrocarbons, Fluorinated; C533928:difluoroethyne