Hydrogen bonds between ammonium ions and aromatic rings exist and have key consequences on solid-state and solution phase properties

A very small azaphane that exhibits high a. nity for H+ has been synthesised. Included protons are stabilised by a charge-assisted NH-pi interaction and hence the bound proton is effectively solvated by the aromatic ring. Exchange of H+ is slow on the H-1 NMR time scale and the conformational characteristics of the macrobicycle are highly pH dependent.