ESR and ENDOR Studies on a 5-O-membered Crown Ether Bearing a Triphenylmethyl Moiety

Article abstract of DOI:10.1002/omr.1270210608

A new 5-O-membered crown ether spin-lebelled with a triphenylmethyl group was prepared.The intramolecular unpaired ?-electron delocalization was investigated by ENDOR.The ENDOR of the crown methylene group adjacent to the aromatic ring revealed non-equivalence in the magnitude of the proton hyperfine splittings.Based on temperature-dependent ENDOR line separation, the activation energy of the conformational change of the methylene protons was estimated.Upon metal chelation into the crown ring the dissociation of the dimer to the monomer radical was greatly affected, and an increase in the activation energy of the vibrating methylene protons was detected.