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ESR and ENDOR studies on a 5‐O‐membered crown ether bearing a triphenylmethyl moiety
Author(s) -
Tajima Kunihiko,
Shimizu Hiroaki,
Morita Takaaki,
Tomoda Hideyuki,
Mukai Kazuo,
Ishizu Kazuhiko
Publication year - 1983
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/omr.1270210608
Subject(s) - methylene , chemistry , unpaired electron , moiety , crown ether , dimer , intramolecular force , ring (chemistry) , crystallography , photochemistry , dissociation (chemistry) , ether , ring size , hyperfine structure , stereochemistry , medicinal chemistry , ion , radical , organic chemistry , physics , quantum mechanics
A new 5‐O‐membered crown ether spin‐labelled with a triphenylmethyl group was prepared. The intramolecular unpaired π‐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 the 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.