19F n.m.r spectra of heptafluoroisoquinoline and hexafluoro-1-methoxyisoquinoline. Long-range inter-ring coupling constants

An analysis of the ¹⁹F n.m.r. spectra of heptafluoroisoquinoline and hexafluoro-1-methoxyisoquinoline is presented. As in heptafluoroquinoline, the inter-ring F? F coupling constants alternate in sign and magnitude and are positive over an odd number of bonds. They correlate with SCFMO carbon–carbon polarizabilities and this infers that the long-range coupling mechanism is dominated by the contribution from the π-electron system.