[GRAPHICS] Self-assembled ionophores, formed by hydrogen bonding of isoG 1 around a cation, are dynamic structures. Multinuclear NMR spectroscopy in CD3CN-CDCl3 showed that cation exchange is >10(4) faster than exchange of isoG 1 ligand in (isoG 1)(10)-Cs+ Ph4B-. The cationic guest also affected the kinetic stability of the complex. 2D-EXSY NMR experiments in CDCl3 showed that ligand exchange was 2 orders of magnitude faster for the Li+-decamer than for the Cs+-decamer.