Electrochromism of Ferrocene- and Viologen-Based Redox-Active Ionic Liquids Composite

Abstract

Redox-active ionic liquids (RAILs) require no other additional reagents such as solvent and supporting electrolyte for electrochemical reactions under undiluted condition. Viologen-based RAILs are one of the electrochromic (EC) ionic liquids with sharp color contrast and high chemical stability. An operation of an EC cell requires two electroactive elements, an EC material and a charge compensating material. In this study, an equimolar composite of a viologen-based RAIL as the EC material and a ferrocene-based RAIL as the charge compensation material, was synthesized and applied to an EC cell. The EC cell with the composite RAIL of as high concentration as 0.92 M each redox species showed good coloration efficiency (91.4 cm2 C–1 at 540 nm on 1.0 V). The coloration process of the EC cell was diffusion-limited process. The current and absorbance of the EC cell reached constant values at large enough bias voltage because of the charge recombination between reduced viologens and oxidized ferrocenes. The recombination affected rapid color erasing process. Almost no deterioration of the composite RAIL was found by 1H NMR after 13 000 potential cycle durability experiment.

Ionic Liquid‐Based Stimuli‐Responsive Functional Materials

“…[136] IL-based electrochromic materials have gradually received more attention and become a promising research field due to their great potential in smart windows and electronic display devices. [137][138][139][140][141] In this context, a novel triphenylamine derivative-linked ionic liquid, 1-(6-((4-(bis(4-(thiophen-2-yl)phenyl) amino)-benzoyl)oxy)hexyl)-3-methyl-imidazolium tetrafluoroborate (TTPAC 6 IL-BF 4 ), has been synthesized and used as a functional electrolyte in smart windows. The result indicated that the IL-based electrolytes presented a faster electrochromic switching time than the traditional electrolytes without ILs unit, attributing to the improved ionic conductivity and ion diffusion coefficient with the introduction of ionic liquid segment as shown in Figure 23a.…”

Recent Advances on Stimuli‐Responsive Smart Materials and their Applications

“…Ferrocene appended redox systems have shown remarkably stable oxidation thereby emerging materials in electrochromic devices . Aida et al ., reported ferrocene appended four pyridyl arms facilitate supramolecular nanotubes to nanorings interconversions via redox‐mediated process .…”

“…Molecular structures of voltage responsive systems. References[43][44][45][46][47][48][49][50][51][52][53][54][55][56][57].…”

The Effect of Oligo(Ethylene Oxide) Side Chains: A Strategy to Improve Contrast and Switching Speed in Electrochromic Polymers

“…Electrochromic (EC) materials, with reversibly switching the absorption properties through electrochemical redox process, have been extensively investigated for decades, owing to their promising applications in energy‐saving smart windows, glasses, data‐storage and camouflage devices, and electronic displays etc. Since the first demonstration of tungsten trioxide (WO 3 ) as an EC material by Deb in 1969, a series of EC materials including metal oxides, Prussian Blue, viologens and conjugated polymers have sprung up. Among these materials, conjugated polymers gradually stand out by virtue of their prominent advantages, such as feasible processability, high optical contrast, low oxidation potential and easily adjustable properties through structure modifications .…”