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Revisiting aqueous redox process of alkyl-linked bis-viologen: Evaluation of redox potential inversion

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タイトル: Revisiting aqueous redox process of alkyl-linked bis-viologen: Evaluation of redox potential inversion
著者: Sagara, Takamasa / Eguchi, Hitomi
発行日: 2019年 2月 1日
出版者: Elsevier Ltd.
引用: Electrochimica Acta, 295, pp.215-223; 2019
抄録: Redox reactions of highly water-soluble bis-viologens were examined at Au electrodes using ultra-micro electrode steady state voltammetry and electroreflectance methods in addition to conventional voltammetry. A bulk UV-vis absorption spectral approach was also used. Alkane-1,n-diyl bis-viologens appeared as a class of prototypical electroactive molecule possessing two equivalent redox centers; they undergo two-consecutive one-electron transfer processes. When intramolecular dimerization takes place immediately after accepting the second electron to produce a form having two viologen radical cation (V•+) sites in one molecule, the second reduction potential may be more positive than the first one. This redox potential inversion is caused by strong tendency to form a stable intramolecular π−π stacking between the two V•+ sites. The redox potential inversion of a highly water-soluble bis-viologen with a butane-1,4-diyl linkage was quantitatively obtained to be 116 mV (E1 – E2 = -116 mV). In contrast, the bis-viologen with an ethane-1,2-diyl linkage exhibited no dimerization below 0.2 mM, and its second redox potential was found to at 63 mV more negative than the first (E1 – E2 = 63 mV), highlighting repulsive interaction. The value of E1 – E2 = -116 mV for the bis-viologen with a butane-1,4-diyl linkage corresponds to the attractive interaction energy in the redox process of 5.9 kBT of room temperature; this value is apparently the same as the dimerization Gibbs free energy of methyl viologen in water.
キーワード: bis-viologen / dimerization / two-consecutive one-electron transfer / electroreflectance / ultra-micro electrode
URI: http://hdl.handle.net/10069/38722
ISSN: 00134686
DOI: 10.1016/j.electacta.2018.10.052
権利: ©2019 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
資料タイプ: Journal Article
原稿種類: author
出現コレクション:060 学術雑誌論文

引用URI : http://hdl.handle.net/10069/38722



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