Electrochemistry Viologen

further reduction yields yellow quinoid compound. diquaternary derivatives of 2,2 -bipyridyl give green radical anion.

in extended viologens, conjugated oligomers such based on aryl, ethylene, , thiophene units inserted between pyridine units. bipolaron di-octyl bis(4-pyridyl)biphenyl viologen 2 in scheme 2 can reduced sodium amalgam in dmf neutral viologen 3.

the resonance structures of quinoid 3a , biradical 3b contribute equally hybrid structure. driving force contributing 3b restoration of aromaticity biphenyl unit. has been established using x-ray crystallography molecule is, in effect, coplanar slight nitrogen pyramidalization, , central carbon bonds longer (144 pm) expected double bond (136 pm). further research shows diradical exists mixture of triplets , singlets, although esr signal absent. in sense, molecule resembles tschischibabin s hydrocarbon, discovered during 1907. shares molecule blue color in solution, , metallic-green color crystals.

compound 3 strong reducing agent, redox potential of −1.48 v, again because aromaticity restored. compound liquid crystal multiple liquid crystal phases in melt result of molecule s structure flat , rigid core , flexible linear alkyl branches.

viologen catalysts have been reported have potential oxidize glucose , other carbohydrates catalytically in mildly alkaline solution, makes direct carbohydrate fuel cells possible.