Rigid and Compact Binuclear Bis‐hydrated Gd‐complexes as High Relaxivity MRI Agents
Loredana Leone, Luca Guarnieri, Jonathan Martinelli, Massimo Sisti, Andrea Penoni, Mauro Botta, Lorenzo Tei
Abstract
Abstract The first binuclear Gd‐complex of the 12‐membered pyridine‐based polyaminocarboxylate macrocyclic ligand PCTA was synthesized by C−C connection of the pyridine units through two different synthetic procedures. A dimeric AAZTA‐ligand was also synthesized with the aim to compare the relaxometric results or the two ditopic Gd‐complexes. Thus, the 1 H relaxometric study on [Gd 2 PCTA 2 (H 2 O) 4 ] and on [Gd 2 AAZTA 2 (H 2 O) 4 ] 2− highlighted the remarkable rigidity and compactness of the two binuclear complexes, which results in molar relaxivities (per Gd), at 1.5 T and 298 K of ca. 12–12.6 mM −1 s −1 with an increase of ca. 80 % at 1.5 T and 298 K (+70 % at 310 K) with respect to the corresponding mononuclear complexes.