A new type of heterocyclic compound was introduced into diethylenetriamine pentaacetic (DTPA) by acylation reaction. The new ligand was then coordinated to Gd3 , Mn2 and Fe3 , respectively. The paramagnetic metal complexes were gained. The structures of heterocyclic compound, new DTPA ligand and metal complexes were characterized by FTIR, elemental analysis and 1HNMR. The longitudinal relaxivity (r1) was also measured. The results showed that the r1 of the Gd3 complex (13.20 mmol?L-1?s-1) and Mn2 complex (12.11 mmol?L-1?s-1) were both higher than that of MRI contrast agent Gd-DTPA (3.62 mmol?L-1?s-1) used in clinic. In addition, the thermodynamical parameters of the interaction between the metal complexes and bovine serum albumin (BSA) were conducted by isothermal titration calorimetry (ITC). The Ka of Gd complexes, Mn complexes and Fe complexes were determined to be 1.17?06, 2.91?05 and 4.04?04, respectively.