Hydrates of gadolinium diethylenetriaminepentaacetic acid bis(methylamide)as studied by X-ray diffraction

The crystal structures of two hydrates of the title compound (gadodiamide I and III) have been determined by single-crystal X-ray diffraction. Gadodia mide I crystallises in the noncentrosymmetric orthorhombic space group P2(1 )2(1)2(1), with two complexes in the asymmetric unit and 10 molecules of wa ter. Gadodiamide III crystals are centrosymmetric and monoclinic, belonging to the space group P2(1)/n, with one independent complex in the unit cell and seven molecules of water. The molecular structures are found to be very similar with respect to metal coordination as well as ligand geometry. Hyd rogen-bond interactions appear to be of decisive importance in the evolutio n of the different hydrates.