Synthesis and characterization of the ligand,[10-( α -tetradecylcarboxymethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid,H 4 L]and its Gd (Ⅲ) chelate are described.Protonation constants for H 4 L(lgK iH =10.62,9.50,4.74,4.12)and the stability constant for GdL - (lgK GdL - =24.60)were determined by potentiometric titrations.The results obtained show that the basicity of the ligand is not significantly altered and the ligand still maintains the strong chelating properties of the parent DOTA after introduction of a linear chain tetradecyl group at the acetic side chain of DOTA.
Synthesis and characterization of the ligand, [2-tetradecyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecan-1,11-dioic acid, H5L] and its Gd(Ⅲ) chelate are described. Protonation constants for H5L (lgKiH = 10.80, 8.40, 4.30, 2.80, 2.15) and the stability constant for GdL2- (lgK■ = 22.75) were determined by potentiometric titration and are similar with the related values of DTPA and Gd-DTPA respectively. The results obtained show that the basicity of the ligand and the stability constant of its Gd(Ⅲ) chelate are not obviously altered after introduction of a linear chain tetradecyl group at the terminal acetic acid residue of DTPA.
