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Resonance Raman spectra of radical cations of bridged diquaternary salts of 2,2′‐bipyridine
Author(s) -
Barker David J.,
Cooney Ralph P.,
Summers Lindsay A.
Publication year - 1985
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250160409
Subject(s) - chemistry , delocalized electron , raman spectroscopy , radical , radical ion , photochemistry , moiety , aromaticity , methylene , resonance (particle physics) , bond order , crystallography , bond length , stereochemistry , ion , medicinal chemistry , crystal structure , organic chemistry , molecule , physics , particle physics , optics
Raman spectra are reported for several bridged diquaternary salts of 2,2′‐bipyridine. Resonance Raman spectra and some excitation profiles of the coloured radical monocations obtained from the diquaternary salts by one‐electron reduction are also reported. Selected frequencies of the parent dications are correlated with changes in the torsional angle between the aromatic rings of the bipyridinium moiety. These correlations, when applied to the spectra of the radical monocations, suggest that the radicals exhibit reduced torsional angle and increased inter‐ring bond order, compared with the parent dications. These changes are consistent with predictions of increased inter‐ring π‐electron delocalization, associated with radical formation. The torsional angle appears to decrease for the radical monocations with increasing number of bridging methylene groups. This is opposite to the trend known to occur in the parent dications.