Redox and magnetic switching in 1,3,5-acceptor-substituted benzenes: reversible formation of radical anions, dianions and trianions in doublet, triplet, and quartet spin states

Abstract

1,3,5-Tris(dicyanovinyl)-substituted benzene 1 can accept one, two, and three electrons stepwise, as shown by (spectro)electrochemical methods. When the corresponding redox stages are attained by K-metal reduction in THF and 2-methyltetrahydrofuran, paramagnetic resonance and optical techniques can identify equilibria between adjacent redox states and different (para)magnetic stages. It can be shown that the dianion can adopt a triplet state whereas the trianion is present in a doublet and quartet spin multiplicity. Similar findings are established for the methoxy-substituted derivative 2. The formation of the different paramagnetic stages is closely connected to the association of the anions with alkali-metal countercations.