1hJFH coupling in 2-fluorophenol revisited: is intramolecular hydrogen bond responsible for this long-range coupling?

Abstract

The present study shows that a hydrogen bond between the OH group and the fluorine atom is not involved in the 1hJFH spin–spin coupling transmission either for 4‐bromo‐2‐fluorophenol or 2‐fluorophenol. In fact, according to a quantum theory of atoms in molecules analysis, no bond critical point is found between O‐H and F moieties. The nature of the transmission mechanism of the Fermi contact term of the 1hJFH spin–spin coupling is studied by analyzing canonical molecular orbitals (see J. Phys. Chem. A 2010, 114, 1044), and it is observed that virtual orbitals play only a quite minor role in its transmission. This is typical of a Fermi contact term transmitted mainly through exchange interactions owing to the overlap of proximate electronic clouds; therefore, it is suggested to identify them as nTSJFH coupling where n stands for the number of formal bonds separating the coupling nuclei. In the cases studied in this work is n = 4. Results presented in this work could provide an interesting rationalization for different experimental signs known in the current literature for proximate JFH couplings.