Stable <i>N, N</i>′‐Di‐<i>tert</i>‐butyl‐meta‐phenylene‐bisnitroxides—Unexpected Ground‐State Singlets

Abstract

In contrast to m-xylylene and related diradicals, bisnitroxide 1 has a singlet ground state according to ESR spectroscopic investigations. Diradical 1 can be isolated as two stable atropoisomers. In both, the free electron is possibly localized on the oxygen atom, because conjugation is prevented by the steric hindrance of the methyl groups. The parent compound with an unsubstituted benzene ring has a triplet ground state.