Modern zethrene chemistry

This paper gives a brief summary of zethrene chemistry after the pioneering works by Clar, Mitchell, Sondheimer, and Staab et al. In the past a few years, various synthetic methods and stabilizing strategies have been developed, which have made the synthesis of stable, vertically and laterally extended zethrenes practically achievable. One of the most important discoveries for this type of molecule is their open-shell diradical character, which is the origin of their unique optical, electronic, and magnetic properties. The fundamental structure–diradical character–physical property relationships were investigated, and these studies form the basis for the tailored design of more general open-shell singlet diradicaloids with controllable diradical character and physical properties.