A redox-active ionic liquid manifesting charge-transfer interaction between a viologen and carbazole and its effect on the viscosity, ionic conductivity, and redox process of the viologen

Tahara, Hironobu; Tanaka, Yuzuru; Yamamoto, Shoko; Yonemori, Shigeki; Chan, Bun; Murakami, Hiroto; Sagara, Takamasa

doi:10.1039/d0sc06244h

Cited by 10 publications

(11 citation statements)

References 68 publications

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“…Because of their fluidity, ILs can act not only as electrochromes but also as electrolytes in electrochromic display devices, which dispense with the problem of strict closure or packaging for preventing the evaporation of volatile solvents. Electrochromic materials with tunable light absorption, reflection, or transmission are currently being pursued for various applications such as smart displays and windows, especially in recent years with memory or energy-saving functions that maintain their colored states even after switching off the applied potentials. − While many existing electrochromic ILs exploit the redox reaction of viologen (or dimethyl-4,4′-bipyridinium dication; Figure a) − because of their prominent electrochromic contrast, stability, and turnover, metal ions in metal complexes (e.g., Co(II)/Co(III) in a chelate metal complex) and metal oxides (V(III)/V(IV)/V(V) in VO 3 ) have also been utilized as redox sources for electrochromism.…”

Section: Electrochromismmentioning

confidence: 99%

Chromic Ionic Liquids

Yoshida

Kitagawa

2021

ACS Appl. Electron. Mater.

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One of the most prominent features of ionic liquids (ILs) is the possible introduction of a desired functionality that is originally inherited from the functional group tethered to its component ions as well as the rational control of liquid properties by selecting the component ions. In this Review, we present the development of ILs with chromism, which is attributed to the colorimetric response to certain external stimuli such as temperature, light, electric field, pH, and chemicals, mainly focusing on the molecular design of the component ions.

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Section: Electrochromismmentioning

confidence: 99%

Chromic Ionic Liquids

Yoshida

Kitagawa

2021

ACS Appl. Electron. Mater.

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“…In contrast, V 2+ may have a charge transfer (CT) band in the presence of a CT donor or a highly polarizable counter anion such as iodide; [1,3] otherwise V 2+ ‐form is colorless. Intriguingly, the CT complex between V 2+ and carbazole is manifested even in a neat ionic liquid as we found very recently (Section 4.3) [4] . The two‐electron reduced neutral form of viologen has low solubility in polar solvents including water; we will put it out of the scope in this Account.…”

Section: Introduction To Viologensmentioning

confidence: 73%

“…To create a new viologen‐based ionic liquid, we prepared an equimolar mixture of carbozole‐based IL and VIL (Figure 12). [4] …”

Section: Viologen‐based Ionic Liquid and Its Application To Dynamic Coloringmentioning

confidence: 99%

Redox of Viologen for Powering and Coloring

Sagara

Tahara

2021

The Chemical Record

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Viologen is among the most attractive and easiest‐to‐use organic redox active group in many functional molecular assemblies. It plays crucial roles as an electron transfer mediator in the artificial photo‐energy conversion systems and electron‐transfer protein assemblies and as a building block of supramolecules. Its features include electrochemically reversible redox activity and stability. Strong blue color and tendency to dimerization of the one‐electron reduced form, viologen mono‐radical mono‐cation, are remarkable. In this Account, we describe the use of viologen to give a powered movement of small molecules and motion of millimetre‐sized macroscopic soft‐matters and the use of viologen ionic liquid as electrochromic materials. Attractivities of the use of viologen units for powering and coloring are demonstrated and discussed. In particular, we highlight driving of mechanical movements by π–π stacking dimerization, incorporation in a hydrogel to attain highly deformable material, induction of 2D phase transformation, and sharp color change of very thin ionic liquid layer in a compartment‐less electrochromic display.

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“…D phys is the viscosity dependent physical diffusion coefficient, which is related to the Stokes–Einstein equation (see eq ). D ex is the electron exchange diffusion coefficient by the electron hopping process, which is related to the rate constant ( k ex ) for electron exchange, concentration ( c ) of the redox species, and average center-to-center distance (δ) between the redox species . The nondiffusional hopping (e.g., Grotthus-like exchange) mechanism of triiodide (see eq ) can be rationalized by the electron exchange diffusion coefficient ( D ex ).…”

Section: Redox Electrolytesmentioning

confidence: 99%

Redox Shuttle-Based Electrolytes for Dye-Sensitized Solar Cells: Comprehensive Guidance, Recent Progress, and Future Perspective

Masud

Kim

2023

ACS Omega

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A redox electrolyte is a crucial part of dye-sensitized solar cells (DSSCs), which plays a significant role in the photovoltage and photocurrent of the DSSCs through efficient dye regeneration and minimization of charge recombination. An I–/I3 – redox shuttle has been mostly utilized, but it limits the open-circuit voltage (V oc) to 0.7–0.8 V. To improve the V oc value, an alternative redox shuttle with more positive redox potential is required. Thus, by utilizing cobalt complexes with polypyridyl ligands, a significant power conversion efficiency (PCE) of above 14% with a high V oc of up to 1 V under 1-sun illumination was achieved. Recently, the V oc of a DSSC has exceeded 1 V with a PCE of around 15% by using Cu-complex-based redox shuttles. The PCE of over 34% in DSSCs under ambient light by using these Cu-complex-based redox shuttles also proves the potential for the commercialization of DSSCs in indoor applications. However, most of the developed highly efficient porphyrin and organic dyes cannot be used for the Cu-complex-based redox shuttles due to their higher positive redox potentials. Therefore, the replacement of suitable ligands in Cu complexes or an alternative redox shuttle with a redox potential of 0.45–0.65 V has been required to utilize the highly efficient porphyrin and organic dyes. As a consequence, for the first time, the proposed strategy for a PCE enhancement of over 16% in DSSCs with a suitable redox shuttle is made by finding a superior counter electrode to enhance the fill factor and a suitable near-infrared (NIR)-absorbing dye for cosensitization with the existing dyes to further broaden the light absorption and enhance the short-circuit current density (J sc) value. This review comprehensively analyzes the redox shuttles and redox-shuttle-based liquid electrolytes for DSSCs and gives recent progress and perspectives.

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A redox-active ionic liquid manifesting charge-transfer interaction between a viologen and carbazole and its effect on the viscosity, ionic conductivity, and redox process of the viologen

Abstract: Redox-active ionic liquids (RAILs) are gaining attention as a material that can create a wide range of functions. We herein propose a charge-transfer (CT) RAIL by mixing two RAILs, specifically...

Cited by 10 publications

References 68 publications

Chromic Ionic Liquids

Chromic Ionic Liquids

Redox of Viologen for Powering and Coloring

Redox Shuttle-Based Electrolytes for Dye-Sensitized Solar Cells: Comprehensive Guidance, Recent Progress, and Future Perspective

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