Azaferrocenophanes with Azobenzene‐Containing Ligands − Protonation and Electrochemical Oxidation of the Molecule Influences the Absorption Spectra and cis−trans Isomerization of the Azobenzene Group

Abstract N ‐{4‐(Phenylazo)phenyl}aminophenyl‐2‐aza‐[3]‐ferrocenophane ( 4 ) and N ‐{3‐(phenylazo)phenyl}aminophenyl‐2‐aza‐[3]‐ferrocenophane ( 5 ) have been prepared by C−N bond‐forming reactions catalyzed by Ru and Pd complexes. The absorption peaks due to the π−π* transition of the trans ‐azobenzene group of 4 and 5 appear at 442 and 426 nm, respectively, in toluene. Photoirradiation of solutions of 4 and 5 at 420 nm causes partial isomerization of the trans ‐azobenzene group to cis ‐azobenzene and reaches a photostationary state. The compounds at the photostationary state undergo thermal isomerization of the cis ‐azobenzene group to the trans isomer. The isomerization after one‐electron oxidation of the compounds takes place more rapidly than that without electrochemical oxidation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)