Intramolecular Electron Transfer between Terminal 1,4-Dimethoxybenzene Units in Radical Cations with a [2.2](1,4)Naphthalenophane, [2.2](1,4)Anthracenophane, and Pentacene Skeleton

摘要

Various radical cations, in which two terminal 1,4-dimethoxybenzene units are anellated to [2.2]paracyclophane (2b~(·+), 3b~(·+)), [2.2](1,4)naphthalenophane, (4d~(·+)), and anthracene bridges (5~(·+)), have been studied by ESR and ENDOR spectroscopy. In the syn- and anti-naphthalenophane radical cations 2b~(·+) and 3b~(·+) the delocalization of the unpaired electron over both π-moieties and the distinct difference between the first and second oxidation potentials, ΔE = E_2~0 - E_1~0, are evidence for a substantial intramolecular electronic interaction between the two electrophores. Extension of the bridge in 4d~(·+) and 5 by benzo anellation results in a localized radical cation. Strong intramolecular electronic interaction between the two electrophores is found in the 1,4,8,11-tetramethoxy-pentacene radical cation (5~(·+)). The syntheses of 4d are described.