First, we attempted to extract metal-chelating groups by clustering the retrieved ligands based on fingerprint similarity and subsequent calculation of the maximum common substructure (MCS). However, in many cases the MCS did not contain the metalchelating atoms (data not shown). Therefore, we retreated to a rule-based approach (Scheme1). As a principle, the metal-chelating groups should contain the atoms coordinated to the metal ion. In addition, the chemical environment of the coordinating atoms was included to obtain a more specific and distinct chemical motif. More details can be found in the experimental section. SCHEME 1 Pipeline to extract metal-chelating groups from the retrieved ligands.