Manganese(I) Diimine(tricarbonyl) Complexes with a Redox-active Free Catechol Unit: Redox-induced Molecular Conversion of Catechol to Quinone by Electrochemical Redox Reactions on the Complex (Supporting Information)

Catechols and their metal complexes are known to participate in electron-transfer reactions in diverse fields. However, most studies have been limited to dioxolene complexes in which the central metal and catechol moieties are directly linked via two adjacent oxygen atoms. Because catechol has oxygen atoms at adjacent positions the oxygen atoms can serve as coordination atoms. In this study, manganese(I) diimine(tricarbonyl) complexes with a free catechol unit are unprecedentedly synthesized to generate an oxidized form, o-quinone, on the complexes. Two types of monodentate ligands are used to control the electronic states of the complexes. Complexes containing the reduced (catechol) form are successfully isolated and characterized using spectroscopic and crystallographic analyses. The redox-responsive nature of the Mn complexes is confirmed by electrochemical analysis. The redox-induced interconversion between the catechol and o-quinone units is observed only in the complex, using electrochemical techniques. This study paves the way for the in situ electrochemical formation of redox-active, unstable organic compounds. Furthermore, the experimental methodologies described herein can establish the redox properties of the resulting species.