Nitrogen NMR : an historical perspective

A compendium of almost 40 years cooperative research with Michal Witanowski and his co-workers on 14 N NMR is presented. The work covers our attempts to produce an understanding of nitrogen nuclear shieldings and the establishment of the nitrogen shielding scale based on neat nitromethane as external standard. Assignment techniques for multiple signal nitrogen NMR spectra are discussed. Applications of 14 N shielding data in the fields of proton exchange, prototropic equilibria and solute-solvent interactions are given. In the latter case contributions to 14 N shielding changes, as a function of solvent, are analysed into specific and non-specific interactions.