Self-Assembly of Radially π-Extended Tetrathiafulvalene Tetramers for Visible and Near Infrared Electrochromic Nanofiber
作者:Masashi Hasegawa、Masahiko Iyoda
DOI:10.1246/bcsj.20190283
日期:2020.1.15
The self-assembly and electrochromic nanofiber formation of radially π-extended tetrathiafulvalene (TTF) tetramers anchored to 1,2,4,5-tetraethynylbenzene were investigated. The tetramer with SBu-substituents underwent self-assembly in solution. Cationic species of the tetramer, obtained by chemical oxidation with Fe(ClO4)3, exhibited a marked electrochromism in the solution. Their electronic spectra revealed absorption bands corresponding to intermolecular mixed-valence aggregation based on (TTF//TTF)•+, and π-aggregation based on (TTF•+//TTF•+) due to the strong molecular association in the cationic species. Furthermore, the tetramer formed an entangled nanoscale fibrous material from CHCl3–hexane. Electrochemical oxidation of the nanofiber on an indium tin oxide electrode revealed a repeatable redox profile. The nanofiber displayed remarkable electrochromic behavior: the color of the fiber changed from purple (neutral) to brown/brownish green (dication and trication) and green (tetracation). These color changes of the nanofiber are similar to those in solution, and the electronic spectra of the oxidized nanofibers reflected the stacked TTF units in the cationic nanofibers.
研究了锚定在 1,2,4,5- 四炔基苯上的径向 π 延伸的四噻吩富戊二烯(TTF)四元分子的自组装和电致变色纳米纤维的形成。带有 SBu 取代基的四聚体在溶液中进行了自组装。通过与 Fe(ClO4)3 化学氧化得到的阳离子四聚体在溶液中表现出明显的电致色性。它们的电子光谱显示了与分子间混合价聚集(TTF//TTF)-+ 和π聚集(TTF-+//TTF-+)相对应的吸收带,这是由于阳离子物种中的分子关联性很强。此外,四聚体还从 CHCl3-hexane 中形成了缠结的纳米级纤维材料。纳米纤维在氧化铟锡电极上的电化学氧化显示了可重复的氧化还原曲线。纳米纤维显示出显著的电致变色行为:纤维的颜色从紫色(中性)变为棕/棕绿色(二阳离子和三阳离子)和绿色(四阳离子)。纳米纤维的这些颜色变化与溶液中的颜色变化相似,氧化纳米纤维的电子能谱反映了阳离子纳米纤维中堆叠的 TTF 单元。