ENDOR of biradicals in liquid solution

The possibility of applying ENDOR in studies of hyperfine interactions in stable biradicals in liquid solution has been explored. The ENDOR spectra of two phenoxy biradicals are reported. Attempts to record ENDOR of some nitroxide and verdazyl biradicals were unsuccessful. The general structure of biradicals spectra and the relaxation processes which may affect the ENDOR effect are briefly discussed.