Electron‐Transfer‐Catalyzed cis → trans Isomerization of 1,1′‐Azonorborane . Prototype of a reversible two‐stage storage system

ESR and cyclic voltammetry investigations show that isomerization of the radical cation of cis ‐1,1′‐azonorbornane ( cis ‐ 1 ) to the trans ‐radical ion proceeds too fast in solution for direct investigation of the cis ‐radical ion even at −78°. The facile isomerization of the radical cation is in agreement with PM 3 calculations proposing an activation barrier of only 17 kJ/mol. As a consequence, quantitative cis → trans isomerization of 1,1′‐azonorbornane can effectively be accomplished by addition of catalytic amounts of one‐electron oxidants. This is the first evidence for a radical‐cation‐catalyzed cis → trans isomerization of azo compounds.