Bipolarons and polaron pairs in oligopyrrole dications

► The structure of oligopyrrole dications is predicted at the density functional theory level. ► Dications n-Py2+ (n < 7) display bipolaron formation spanning the length of 3-4 monomers. ► Singlet ground states of n-Py+2 (6 < n < 16) display a polaron pair as the charge carrier. ► Oligopyrrole dications (n > 17) have a triplet ground state and predominantly a polaron pair. ► Homogeneous phase change from benzenoid to quinoid requires a multiply charged oxidation state.