AAZTA-based bifunctional chelating agents for the synthesis of multimeric/dendrimeric MRI contrast agents.

Monomeric and dimeric bifunctional chelates based on the AAZTA (6-amino-6-methylperhydro-1,4-diazepinetetraacetic acid) platform bearing arylamino and isothiocyanate groups for conjugation to biomolecules were synthesised. Both systems were used for the preparation of high relaxivity dendrimeric (PAMAM G1) and multimeric octa-Gd(III) complexes. These systems show enhanced relaxometric properties attributed to the presence of two coordinated, fast exchanging, water molecules (q = 2) on each metal ion and to a rather rigid and compact molecular structure.