Quinoidal conjugated polymers with open-shell character

pi-Conjugated polymers composed of quinoidal or proquinoidal building blocks represent an intriguing class of macromolecules in terms of both fundamental research and practical applications. They have received increasing research interest in recent years on account of their distinct structural features and unique properties including open-shell electronic configurations and delocalization of polarons. Investigations of the influences of the quinoidal character on optical, electronic, and magnetic properties demonstrated a great prospect of these polymers in diverse application fields. This review summarizes the recent development of quinoidal conjugated polymers with regard to design, synthesis, fundamental properties, and representative applications, with emphasis on their open-shell character and high-spin materials properties. The challenges and outlook associated with this research field are also discussed.