Abstract
A novel ligand, diethylenetriamine-N,N″-bis(acetyl-isoniazid)-N,N′,N″-triacetic acid (H3L) has been synthesized from diethylene triamine pentaacetic acid (DTPA) and isoniazid. Ligand and its five neutral rare earth (RE=La, Sm, Eu, Gd, Tb) complexes holding promise of magnetic resonance imaging (MRI) were characterized on the basis of elemental analysis, molar conductivity, 1H-NMR spectrum, FAB-MS, TG-DTA analysis and IR spectrum. The relaxivity (R1) of complexes and Gd(DTPA)2− used as a control were determined. The relaxivity of LaL, SmL, EuL, GdL, TbL and Gd(DTPA)2− were 0.14, 1.66, 3.14, 6.08, 2.79 and 4.34 l·mmol−1·s−1, respectively. The spin-lattice relaxivity of GdL was larger than that of Gd(DTPA)2−. The relaxivity of GdL had also been investigated in human serum albumin (HSA) solution, the relaxivity of GdL was enhanced from 6.08 l·mmol−1·s−1 in water solution to 9.09 l·mmol−1·s−1 in HSA solution. In addition, thermodynamics stability constant of GdL complex was determined, the thermodynamic stability constant of GdL complex (KGdL=1020.84) was a few larger than that of Gd(DTPA)2− (KGd-DTPA=1020.73). The results showed that complex of GdL may be a prospective MRI contrast agent with low osmotic pressure due to non-ion complex, high spin-lattice relaxivity, good stability and binding affinity for the serum protein.
