Gd-complexes of macrocyclic DTPA conjugates of 1,1′-bis(amino)ferrocenes as high relaxivity MRI blood-pool contrast agents (BPCAs)

We report the synthesis of macrocyclic DTPA conjugates of 1,1′-bis(amino)ferrocenes (1a–b) and their Gd-complexes [Gd(L)(H2O)] (2a–b, L = 1a–b) for use as new MRI blood-pool contrast agents. High R1 relaxivity in HSA as well as high thermodynamic and kinetic stabilities is observed for 2a.