**3. Classification of Schiff bases and their metal complexes**

By coordinating the d-block metal ion with the electron-donating ligand atom, a complex is created that modifies the metal's steric and electrical properties. By doing so, the metal ion's reactivity is stabilized and regulated, which is especially helpful for ions at higher oxidation states where they are less stable. Auxiliary ligands, or Schiff bases, are compounds that modify the structure and reactivity of a transition metal ion inside a complex. On the other hand, they do not incur any irreversible modifications, unlike reactive ligands. Atoms like nitrogen, sulfur, or oxygen can act as donors in the coordination process.
