3-b]phenazine (20). For 5 and 20 a large difference (ΔE° ≥400 mV) between the first and second reduction potentials was found. The ESR results of the radical anion 20•– are in support of a strong homoconjugation. ESR studies of 4•–, 13•–, and 17•– also reveal a symmetrical displacement of the unpaired electron over both acceptor groups on the ESR time scale which, however, based on the small potential