To Isomerize or not to Isomerize? E /Z Isomers of Cyclic Azobenzene Derivatives and their Reactivity upon One-Electron Reduction.

Azo compounds are efficient electron acceptors. Upon one-electron reduction they generally isomerize forming the thermodynamically most stable radical anion. Here we show that the size of the central ring in 1,2-diazocines and diazonines has a ruling influence on the configuration of the one-electron reduced species. Markedly, diazonines, which bear a central nine membered heterocycle, show light induced E/Z isomerization, but retain the configuration of the diazene N=N moiety upon one-electron reduction. Accordingly, E/Z isomerization is not induced by reduction.