Synthesis, characterization, thermal constant and relaxation of gadolinium(III), iron(III) and manganese(II) chelates of diethylenetriamine-bis-inositol-N,N′,N″-triacetic acid

The reaction of the bicyclic anhydride of diethylenetraiamine-pentaacetic acid (DTPAA) with inositol gave diethylenetriamine-inositol-biester-N,N′,N″-triacetic acid (DTPA-BI) (1). (1) was characterized by FAB-MS, 1HNMR, IR and elemental analysis. Its chelates of Gd(III), Fe(III) and Mn(II) holding promise of magnetic resonance imaging (MRI) were synthesized. Gd(III) complex was obtained from Gd2O3 and the acid form of (1). Thermodynamic stability constant and relaxation of Gd(III) complex with DTPA-BI were determined. The spin–lattice relaxivity (R1=5.6 l mmol−1 s−1) of chelate was slightly larger than that of [GdDTPA]2−. The results showed that the complex is a prospective MRI agent, although thermodynamic stability constant of DTPA-BI K[GdDTPA-BI]−=1018.2 was a little less than that of [GdDTPA]2− (K[GdDTPA]2−=1020.73).