The invention relates to a novel class of ligands, complexes comprising such ligands and a metal ion, and adducts of these metal complexes and a macromolecule. Pharmaceutical compositions and methods of making and using the ligand-metal complexes are also described. The invention also relates to the use of macromolecular adducts for enhancement of diagnostic imaging. In particular, the invention relates to (ethylene)-(propylene)-triaminepentaacetic acid (EPTPA) derivatives, a process for their production, and their use for the production of pharmaceutical agents for NMR diagnosis or radiodiagnosis or radiotherapy.