A new nonionic macrocyclic gadolinium(III) chelate as a potential magnetic-resonance-imaging contrast agent

A new GdIII complex of a 17-membered macrocycle with three pendant carboxymethyl groups has been synthesized; the ligand has been obtained in a single step from diethylenetriaminepentaacetic dianhydride (pentetic dianhydride) and 1,4-butanediamine (putrescine). An X-ray crystal analysis has shown that the complex is a nonionic metal chelate with a coordinated water molecule. The near-zero electrical conductivity, 1 omega-1 cm2 mol-1, of a 1 mM solution indicated that the metal chelate is essentially undissociated. The NMR T1 relaxivity is 2.5 s-1 mM-1 at a resonance field of 64 MHz, and 3.4 s-1 mM-1 at 250 MHz. This new GdIII complex is a potentially important magnetic resonance imaging contrast agent.