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Resolving an apparent discrepancy between theory and experiment: spin–spin coupling constants for FCCF
Author(s) -
Del Bene Janet E.,
Provasi Patricio F.,
Alkorta Ibon,
Elguero José
Publication year - 2008
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.2304
Subject(s) - chemistry , coupling constant , propagator , coupled cluster , ab initio , spin (aerodynamics) , atomic physics , dipole , ab initio quantum chemistry methods , coupling (piping) , molecular physics , molecule , physics , quantum mechanics , thermodynamics , organic chemistry , mechanical engineering , engineering
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 (FF) 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 CC and CF 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 (CC), 1 J (CF), and 2 J (CF) have also been reported and compared with experimental data. While 1 J (CF) is in agreement with experiment, the computed value of 2 J (CF) is larger than our estimate of the experimental coupling constant. Copyright © 2008 John Wiley & Sons, Ltd.