Organic Mixed-Valence π-Electron Systems—Current Status and Challenges

Abstract

Over the past few decades, our understanding of organic mixed-valence (MV) chemistry has advanced dramatically. During this period, the remarkable properties of MV states, arising from combinations of diverse π-bridging units and redox-active centers, have been elucidated. Currently, further progress is anticipated through sophisticated molecular design that utilizes the specific characteristics of each constituent unit. This review outlines the evolution of organic MV chemistry, discusses design principles, identifies unresolved challenges, and highlights emerging trends aimed at addressing them. Key areas of focus include deepening our understanding of the dynamic aspects of MV states (including molecular vibrations), developing novel MV systems by effectively utilizing both intramolecular and intermolecular MV states, and the molecular design, development, and characterization of multi-redox-centered MV multi-radical systems.