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EPR study of Bi‐, Ter‐ and quaterthiophene radical cations
Author(s) -
Kirste Burkhard,
Tian Peizhu,
Kossmehl Gerhard,
Engelmann Gunnar,
Jugelt Werner
Publication year - 1995
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.1260330112
Subject(s) - chemistry , steric effects , mndo , electron paramagnetic resonance , conformational isomerism , radical , spin density , computational chemistry , photochemistry , spectroscopy , crystallography , stereochemistry , molecule , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics , condensed matter physics
Radical cations of a series of α‐methyl‐substituted bi‐, ter‐ and quaterthiophenes were investigated by EPR and, in part, ENDOR spectroscopy. In the case of terthiophenes, the electronic and steric effects of methyl substituents were studied. The experimentally determined spin density distributions were rationalized by means of semi‐empirical quantum‐mechanical calculations (MNDO, PM3, RHF‐INDO/SP). Sterically non‐hindered oligothiophene radical cations are planar and form mixtures of cis and trans conformers, whereas uniform species were observed in the case of sterically hindered, non‐planar radical cations.