Schiff Base and Reduced Schiff Base Ligands

AbstractSupramolecular chemistry of Schiff base ligands and their reduced homologues is rapidly growing and gaining increased attention due to their convenient and straightforward synthetic methods and a wide range of complexation modes with almost all types of metal ions. In fact, the phenomenon of molecular recognition, self‐organization and self‐assembly, and host–guest chemistry through covalent and noncovalent interactions is pivotal to the understanding and development of supramolecular chemistry. In this direction, several forms of acyclic and macrocyclic Schiff bases and their reduced forms are employed to gain more insights and correctly ascertain the effect of different donor atoms, their relative position, the number and size of the chelating rings formed, the flexibility, and the geometry around the coordinating moiety on the molecular recognition process and selective binding of cations, anions, and/or neutral species. In this connection, this chapter deals with the supramolecular and molecular recognition properties and interesting host–guest complexes and metalla–supramolecular network structures derived from several acyclic and cyclic Schiff bases and reduced Schiff base ligands. Various solid‐state metalla‐supramolecular network structures are delineated ranging from hydrogen‐bonded linear polymers and helical coordination polymers, and 2D sheets to 3D network architectures constructed via N H⋯O, C O⋯H Osolvent, O H⋯O, N H⋯O C, hydrogen bonds and C O⋯π, C H⋯π, and π–π stacking interactions. This review gives an account of the observed structural diversity in relation to the role of different donors and acceptors, aqua ligands and solvents, nature of the ligands and metal ions, and the coordination geometry around the metal ions.