• Bulletin of the Korean Chemical Society
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• v.35 no.11
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• pp.3143-3155
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• 2014

This tutorial review provides a general account of the electrochemical behavior of quinones and their various applications. Quinone electrochemistry has been investigated for a long time due to its complexity. A simple point of view is developed that considers the relative stability of the reduced quinone species and the values of the first and second reduction potentials. The 9-membered square scheme in buffered aqueous solutions is explained and semiquinone radical stability is discussed in this context. Quinone redox reaction has also been employed in various studies. Diverse examples are presented under three broad categories defined by the roles of quinone: molecular tool for physical chemistry, versatile electron mediator, and charge storage for energy conversion devices.

• Bulletin of the Korean Chemical Society
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• v.19 no.2
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• pp.212-217
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• 1998

The electrochemistry and valence tautomerism of CoⅢ(N-N)(SQ)(Cat), [N-N=N,N,N',N'-tetramethylethylenediamine (TMEDA); SQ=3,5- or 3,6-di-tert-butyl-semiquinone, Cat=3,5- or 3,6-di-tert-butyl-catechol], have been investigated by spectroscopic, electrochemical, spectroelectrochemical methods in nonaqueous solvents under anaerobic condition. The transition temperature between tautomers is dependent upon the donation effect of substituted quinone ligand and solvent. It increases with the increase of donation effect of solvent and quinone ligand. CoⅢ(TMEDA)(SQ)(Cat) is reduced to [CoⅡ(TMEDA)(SQ)(Cat)]-, and then reduces to [CoⅡ(TMEDA)(Cat)2]2-. CoⅢ(TMEDA)(SQ)(Cat) is oxidized to [CoⅢ(TMEDA)(SQ)2]+, but the stability of the oxidized form in DMF is dependent upon the solution temperature. With the increase of solution temperatrue the oxidized form may be converted to [CoⅡ(TMEDA)(SQ)(BQ)]+ by intramolecular electron transfer from SQ ligand to CoⅢ.