text: The term Schiff base is normally applied to these compounds when they are being used as ligands to form coordination complexes with metal ions. One example is Jacobsen's catalyst. The imine nitrogen is basic and exhibits pi-acceptor properties.  Several, especially the diiminopyridines are noninnocent ligands. Many Schiff base ligands are derived from alkyl diamines and aromatic aldehydes.
  Chiral Schiff bases were one of the first ligands used for asymmetric catalysis. In 1968 Ryōji Noyori developed a copper-Schiff base complex for the metal-carbenoid cyclopropanation of styrene.  Schiff bases have also been incorporated into metal–organic frameworks (MOF).