Nuclear magnetic resonance lineshape of a centrosymmetric array of four spin-½ nuclei. Structure of 4,4′-difluorobiphenyl

Abstract

A method is described for calculating the nuclear magnetic resonance lineshape for a centrosymmetric array of four spin-½ nuclei. The four-spin Hamiltonian was exactly diagonalized numerically and the effects of other nuclei were included approximately by using a Gaussian broadening function on the calculated multiplets. Application of the method to the analysis of experimental n.m.r. spectra for a single crystal of 4,4′-difluorobiphenyl showed that they are consistent with a model in which the protons occur in linear centrosymmetric groups of four, implying that the molecules are planar in the solid state. Interproton distances within the group were determined accurately.