Redox-induced Conformational Changes in 1,3-Propylene- and<i>m</i>-Xylylenebis[5-(10-butyl-5,10-dihydrobenzo[<i>a</i>]indolo[2,3-<i>c</i>]carbazole)]: Twin-BIC Donors that Form Sandwich-like Dimeric Cations Exhibiting NIR Absorption

Abstract

The title electron-donors with two units of a disk-shaped heterocyclic diamine undergo two-stage stepwise one-electron oxidation to the corresponding cation radicals and dication diradicals. They adopt a stacked geometry as in pimers and π-dimers, respectively. In contrast, the third and fourth oxidation processes occur nearly at the same potential, indicating that tricationic/tetracationic species prefer the extended geometry. The similar redox-induced conformational changes were not observed in 1,5-pentylene or o-xylylene derivatives, which prefer the extended geometry irrespective of the oxidation states.