Radical pair formation in X-irradiated croconate ions: A single crystal ESR study

Abstract

The crystal structure of CsNa(C 5O 5) has been determined and shows that the croconate rings stack along the crystallographic a direction. Single crystals of this compound have been X-irradiated at 77 K. The angular dependence of the resulting ESR signals shows that a radical pair is trapped; the corresponding electron-electron dipolar interaction indicates that the vector which links the two components of the pair is aligned along the stacking direction and is consistent with a pair formed by two paramagnetic croconate anions separated by a (C 5O 5) 2- ring.