Switching of Redox Properties Triggered by a Thermal Equilibrium between Closed‐Shell Folded and Open‐Shell Twisted Species

Thermally switchable redox properties have been reported to be due to a change in the spin state of newly designed overcrowded ethylenes, which can adopt closed‐shell folded and open‐shell twisted forms. In this study, tetrathienylanthraquinodimethane derivatives were designed to be in thermal equilibrium between a more stable folded form and less stable but more donating twisted diradical in solution, so that the oxidation potential can be controlled by heating/cooling. This is the first example of a switching of redox properties based on a thermally equilibrated twisted diradical, which can be more readily oxidized to the twisted dication. Erwärmend: Das Oxidationspotential von Anthrachinodimethan‐Derivaten lässt sich durch Erwärmen/Abkühlen in Lösung aufgrund einer Änderung des Spinzustands reversibel schalten. In diesem seltenen Beispiel schaltbarer Redoxeigenschaften, das auf einem thermisch im Gleichgewicht befindlichen verdrehten Diradikal basiert, kann das verdrehte Diradikal leichter oxidiert werden als die gefaltete Form (siehe Schema).