(19)F spin-spin coupling in peri-difluoronaphthalene.
We report first-principles electronic structure calculations of the nuclear magnetic resonance (NMR) spin-spin coupling tensors to the (19)F nucleus in peri-difluoronaphthalene. This system was recently subjected by Emsley and co-workers to an experimental liquid crystal NMR study, and the 4-bond (19)F(19)F coupling was found to have a significant anisotropic contribution. We use density-functional theory (DFT) with different exchange-correlation functionals and the polarisation-consistent basis sets optimised for J-coupling, as well as the second-order polarization propagator approximation, to calculate all the coupling tensors involving the (19)F nuclei in this molecule. The tensor components, combined with the experimental orientation tensor, confirm the sign and order of magnitude of the anisotropic part of the spin-spin coupling: the value derived experimentally is -31.6 Hz versus our different quantum chemical results at around -10 Hz. Besides the (4)J(FF) tensor, significant anisotropic contributions are found also for the long-range (13)C(19)F and (1)H(19)F coupling tensors.
Jaszuński
Michał
M
Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01224, Warsaw, Poland. michaljz@icho.edu.pl
Vaara
Juha
J