Syntheses, crystal structures and properties of two Mn(II) complexes of DTPA-bisamide derivative

Two new Mn(II) complexes of DTPA-bisamide derivative ligand (H5L), MnH3L · CH3OH · 2.5H2O (1) and [Mn2.5L(H2O)8] · 5.25H2O (2) were synthesized and structurally characterized. X-ray structure analyses showed that the two complexes have quite different structures. In complex 1, Mn(II) cation adopts a novel seven-coordinate distorted pentagonal bipyramid polyhedron, while in complex 2, four different Mn(II) coordination environments are observed and form a novel 1-D zigzag coordination chain. Complexes 1 and 2 construct the 2-D and 3-D supramolecular architectures through versatile hydrogen bond interactions, respectively. The relaxivity of the two complexes were also determined. The higher R1 value of 2 means that it may be applied in magnetic resonance imaging contrast agents.