π‐Dimers of End‐Capped Oligopyrrole Cation Radicals

In two consecutive one-electron oxidations, oligopyrroles substituted with phenyl capping groups (PhPynPh, n = 2–4) can be oxidized reversibly to give stable cation radicals and dications. Spectroelectrochemical studies give direct evidence that diamagnetic π-dimers of cation radicals are formed in solution. Such dimers may be involved as charge carriers in conducting polypyrrole.