rac-N,N'-Bis(1-ferrocen-yleth-yl)pyridine-2,6-dicarboxamide.

The title compound, [Fe(2)(C(5)H(5))(2)(C(21)H(21)N(3)O(2))], a potential novel N,N',N''-tridentate ligand with (non-crystallographic) C(2) axial symmetry, adopts a U-shaped molecular conformation.

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)(H(2)O)] (2a-b, L = 1a-b) for use as new MRI blood-pool contrast agents. High R(1) relaxivity in HSA as well as high thermodynamic and kinetic stabilities is observed for 2a.