[2.2](4,4')azobenzenophane. Synthesis, structure, and cis-trans isomerization

Abstract The title compound 2 was synthesized by the reduction of 1,2-bis(4'-nitrophenyl) ethane. Spectral data and results of X-ray crystal structure analyses suggest that facing two azobenzene units in 2 are deformed from the planes both in solution and crystal. The cis-cis form of 2 (cc- 2 ), which was generated photochemically, isomerized thermally via the transcis form (tc-2), whose life time was only 22 second at 25°C, to the trans-trans form (tt-2). Due to a short life time of tc-2, the efficiency of photo-isomerization of 2 from tt-2 to cc-2 became light intensity dependent.