Information AboutViologen |
| CATEGORIES ABOUT VIOLOGEN | |
| nitrogen heterocycles | |
| dyes | |
| quaternary ammonium compounds | |
| SHOPPER'S DELIGHT | |
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Further reduction yields a Quinoid compound that is yellow. Diquaternary derivatives of 2,2'-bipyridyl give a green radical anion. Viologens are investigated for use in Electrochromic systems because of their ability to change color reversibly many times upon Reduction and Oxidation . Paraquat is a viologen used as a Herbicide . In extended viologens Conjugated Oligomer s such as based on Aryl , Ethylene and Thiophene units are inserted between the Pyridine units . The Bipolaron di-oktyl bis(4-pyridyl)biphenyl viologen '''2''' in ''scheme 2'' can be reduced by Sodium Amalgam in DMF to the neutral viologen '''3'''. The Resonance Structure s of the quinoid 3a and the Diradical '''3b''' contribute equally to the hybrid structure. The driving force for the contributing '''3b''' is the restoration of Aromaticity with the Biphenyl unit. From X-ray Crystallography it is established that the molecule is Coplanar and with slight nitrogen Pyramidalization and that the central carbon carbon bonds a longer (144 Pm ) than what would be expected for a Double Bond (136 pm). Research further shows that the diradical exists as a mixture of Triplet s and Singlet s although remarkably an ESR signal is absent. In this sense the molecule resembles Chichibabin's Hydrocarbon discovered in 1907 . Compound 3 is a very strong Reducing Agent with a Redox Potential of - 1.48 V again because aromaticity is restored. The compound is also a Liquid Crystal with multiple liquid crystal phases in the melt as a result of the molecule's structure with a flat and rigid core and flexible linear Alkane arms. EXTERNAL LINKS
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