Novel heteroditopic chelate for self-assembled gadolinium(III) complex with high relaxivity.

[Fe(tpy-DTTA)2Gd2] is a self-assembled trinuclear complex based on a novel ligand in which a terpyridine and a poly(amino carboxylate) moiety are connected; it has a well-defined topology with favourable features to attain high relaxivities, i.e. a rigid FeII(tpy)2 core, reduced flexibility at the periphery thanks to a short linker, and efficient separation of the two GdIII centres.