Four novel ester-amino ligands were synthesized by bis-acylation of octadecanyl, hexadecanyl, tetradecanyl and dedecanyl L-lysinate with ethylenediaminetetraacetic acid mono-anhydride (EDTA-MA), respectively. The corresponding neutral dimeric Gd(Ⅲ) complexes were gained by reacting these ligands with GdCl3·6H2O. All ligands and complexes were characterized by FTIR, 1H NMR and elemental analysis. The longitunal relaxation time (T1) was measured, and their stability were investigated by competition with Ca2+ and EDTA. The results indicate that the relaxivity of these netral binuclear Gd(Ⅲ) complexes are higher than that of Gd-DTPA.
