Stereochemistry of rare earth polyaminocarboxylate complexes

Rare earths are an important class of metal ions with a rich coordination chemistry that is key to some of their important applications, i. e. their use as contrast agents in MRI, luminescent probes or radiopharmaceuticals. Stable complexation of these ions in aqueous media is generally achieved with polyaminocarboxylate ligands that satisfy their high coordination numbers (often 7-10). The structures of these complexes are largely determined by the hard acid character of these metal ions and the topology of the ligands. A precise understanding and a careful control of the stereochemistry of these complexes is crucial to design systems with the desired properties. Herein, we provide a detailed overview of the stereochemical features of this important family of complexes, including the different sources of chirality that lead to the formation of different stereoisomers and the analysis of their coordination polyhedra. • Rare earth complexes can exist as different stereoisomers having different properties. • Diastereoisomeric complexes are characterized by different coordination polyhedra. • C-alkylation introduces an additional source of chirality. • The P and S atoms of some functional groups become chiral upon coordination. • Complexes with ligands other than DOTA and DTPA derivatives display similar sources of chirality.