Accelerating water exchange for GdIII chelates by steric compression around the water binding site

The water exchange process was accelerated for nine-coordinate, monohydrated macrocyclic Gd-III complexes by inducing steric compression around the water binding site; the increased steric crowding was achieved by replacing an ethylene bridge of DOTA(4-) by a propylene bridge;double dagger in addition to the optimal water exchange rate, the stability of [Gd(TRITA)(H2O)](-) is sufficiently high to ensure safe medical use which makes it a potential synthon for the development of high relaxivity, macromolecular MRI contrast agents.