Electronic structure elucidation in oxidized metal–salen complexes

Salen ligands are ubiquitous in inorganic chemistry with utility in applications ranging from materials to catalysis. Additionally, salen ligands have the potential for redox-activity due to energetically accessible molecular orbitals. This review will focus on elucidation of the electronic structure in oxidized metal–salen complexes. Due to the highly modular synthesis of these ligands, we present a comprehensive examination of structural factors that play a role in determining the overall electronic structure upon one-electron oxidation. Experimental and theoretical techniques used in the study of oxidized metal-salen complexes are presented, as well as the basics for the interpretation of such techniques. While the emphasis of the review is on complexes of the first-row transition metals, we briefly discuss second- and third-row transition metal–salen complexes, as well as salen-type ligand derivatives.