The present invention relates to new class of dimeric macrocycles capable of chelating paramagnetic metal ions, their chelated complexes with metal ions and the use thereof as contrast agents, particularly suitable for Magnetic Resonance Imaging (MRI) analysis.

The invention relates to a process for the manufacturing of a solution of a dimeric C gadolinium complex, such as [?-[1-[bis[2-(hydroxy-xO)-3-[4,7,10-tris[(carboxy-xO)methyl]-1,4,7,10-tetraazacyclododec-1-yl-?N.sup.1,?N.sup.4, ?N.sup.7,?N.sup.10]propyl]amino]-1-deoxy-D-glucitolate(6-)]]digadoliniumcomplex, which is useful in the field of diagnostic imaging and of contrast agents in Magnetic Resonance Imaging (MRI), comprising the steps of precipitating a portion of free gadolinium metal ions by means of a precipitating agent. The invention further relates to a process for isolating the dimeric gadolinium complex from said solution, and to the solution and the isolated dimeric gadolinium complex obtainable by such processes.

The present invention provides a drug delivery system that overcomes conventional technical problems and that is readily put to practical use. Iron-salen complexes represented by General Formula (I) below. The invention renders iron-salen complexes magnetic, which can thus be used as drugs that can be delivered to affected areas in the body using the inherent magnetic properties of the drug without employing carriers composed of magnetic substances as has been done hitherto. ##STR00001##