Synthesis and Physicochemical Characterization of 1,4,7,10-Tetra (2-glutaryl)-1,4,7,10 Tetraazacyclododecane Lanthanide Complexes

To describe a new tetra-(carboxyethyl) derivative of Gd-DOTA called P730 Gd ( 1): Figure 1. P730 Gd is a precursor in the synthesis of new macromolecular MRI contrast agents. The inner sphere contribution to the relaxivity of gadolinium complexes is determined by the rotational correlation time of the complex τR, the water residence time τM in the first coordination shell and the electronic relaxation time τS ( 2). Each of these main relaxometric parameters is influenced by the structural characteristics of the complexes. Consequently, the structural and the physicochemical properties of each P730 diastereoisomer have been studied by crystallography, NMR and luminescence. In order to avoid complex dissociation, new Gd3+ chelates should be characterized by high thermodynamic stability and transmetallation inertness, therefore the thermodynamic stability constant of P730 Gd was determined and its stability in a model of transmetallation was assessed