19F spin–spin coupling in peri-difluoronaphthalene

Abstract

We report first-principles electronic structure calculations of the nuclear magnetic resonance (NMR) spin–spin coupling tensors to the ¹⁹F 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 ¹⁹F¹⁹F 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 ¹⁹F 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 ⁴J_FF tensor, significant anisotropic contributions are found also for the long-range ¹³C¹⁹F and ¹H¹⁹F coupling tensors.