Coordination chemistry of metal complexes containing salen-type ligands bearing nitro groups

Salen-type ligands are acyclic tetradentate N2O2 donor moieties containing 2 imine groups. By introducing various substituents onto the terminal phenol rings, the electronic properties of these ligands can be tuned to modulate the electronic structures of the coordinated metal ions, thereby imparting diverse functionalities to the corresponding complexes. This review focuses on salen-type ligands bearing electron-withdrawing NO2 groups and summarizes previous studies on the synthesis, structures, and physicochemical properties of their metal complexes.