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Electron spin resonance spectroscopy of free radicals
Author(s) -
Fairhurst Shirley A.,
Sutcliffe Leslie H.,
Preston Keith F.,
Banister Arthur J.,
Partington Andrew S.,
Rawson Jeremy M.,
Passmore Jack,
Schriver Melbourne J.
Publication year - 1993
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260311114
Subject(s) - chemistry , unpaired electron , electronegativity , radical , substituent , protonation , electron paramagnetic resonance , spectroscopy , ring (chemistry) , atomic orbital , resonance (particle physics) , trifluoromethyl , crystallography , photochemistry , electron , nuclear magnetic resonance , stereochemistry , atomic physics , organic chemistry , ion , quantum mechanics , physics , alkyl
Abstract Solution and powder ESR spectra of the 4‐trifluoromethyl‐1,2,3,5‐dithiadiazolyl and 4‐pentafluorophenyl‐1,2,3,5‐dithiadiazolyl free radicals were analysed. Comparison of the ESR parameters with those obtained for the protonated equivalents shows that fluorination produces a drift of unpaired electron spin density away from the nitrogen 2p x orbitals towards sulphur 3p x orbitals (x is the direction perpendicular to the heterocyclic ring), consistent with an increase in electronegativity of the substituent. The fluorinated radicals dimerize more readily than their protonated counterparts.