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A spectroscopic study of the reduction of geometrically restrained viologens

Lookup NU author(s): Professor Andrew Benniston, Emeritus Professor Anthony Harriman, Dr Peiyi Li, James Rostron, Dr Ross Harrington, Emeritus Professor Bill CleggORCiD


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A small series of N,N′-dimethyl-4,4′-bipyridinium dication derivatives (commonly known as viologens) has been synthesized and fully characterized; a short dialkoxy tether attached at the 3,3′-positions is used to alter the central dihedral angle. These angles were determined by both single-crystal X-ray diffraction and by computational studies made for the dication, radical cation, and neutral species in a solvent reservoir. The dihedral angle derived for the dication controls the first reduction potential, whereas the geometry of the resultant π-radical cation determines the magnitude of the second reduction potential. The optical absorption spectra recorded for the various species, and especially those of the radical cations, and the EPR spectral parameters of the π-radical cations also depend on the molecular geometry. In particular, the central dihedral angle influences the spin density distribution around the aromatic nucleus and, by way of comparison to the parent viologen, it has been possible to resolve the angle dependence from the inherent inductive effect of the strap. These results are considered in terms of the degree of electronic communication between the two aromatic rings, as controlled by the length of the tether. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

Publication metadata

Author(s): Benniston AC, Harriman A, Li P, Rostron JP, Harrington RW, Clegg W

Publication type: Article

Publication status: Published

Journal: Chemistry - A European Journal

Year: 2007

Volume: 13

Issue: 28

Pages: 7838-7851

ISSN (print): 0947-6539

ISSN (electronic): 1521-3765

Publisher: Wiley - V C H Verlag GmbH & Co. KGaA


DOI: 10.1002/chem.200700872


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