4,8,12,16-tetra-tert-butyl-s-indaceno[1,2,3-cd:5,6,7-c′d′]diphenalene:: A four-stage amphoteric redox system

A four-stage amphoteric redox hydrocarbon (5) containing two phenalenyl units was prepared. X-ray crystallography of 5 reveals a delocalized D-2h structure, which is consistent with the presence of only five signals in the H-1 NMR spectrum of 5 at -60 degrees C, The cyclic voltammogram of 5 exhibits four reversible redox waves with a small numerical sum (E-1(sum)) of first oxidation (E-1(ox)) and reduction (E-1(red)) potentials. Four redox states of 5 were successfully generated from the neutral 5 and were characterized by NMR, ESR, and UV-vis-near-IR spectroscopies and theoretical calculations. These spectral data reveal that phenalenyl units play an important role in the high amphotericity of 5 and the stability of the redox states generated.