13C longitudinal relaxation time measurements and DFT-GIAO NMR computations for two ammonium ions of a tetraazamacrocyclic scorpiand system.

A small contribution of iso-H414+Dhydr (see figure) to an ionic mixture of pentamine 1 was proposed to explain the 'abnormal' 13C NMR shifts observed for atoms C11 and C12 in its side-chain arm, at pH <1.