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

Abstract

AbstractESR 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 PM3 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.