Geometrical and Electronic Structure of Cation Radical Species of Tetraarylanthraquinodimethane: An Intermediate for Unique Electrochromic Behavior

Ishigaki, Yusuke; Fukagawa, Reina; Sugawara, Kentaro; Harimoto, Takashi; Suzuki, Takanori

doi:10.1002/asia.202200914

Cited by 5 publications

(1 citation statement)

References 32 publications

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“…Compared to the previously reported tricolor electrochromic systems in which the intermediary state is an open-shell species that undergoes disproportionation, [47] all of the neutral, dicationic, and tetracationic states in the present systems exhibit thermodynamic stability, as demonstrated by isolation and Xray analysis of each state including the intermediary dicationic state. Drastic geometrical changes among the redox states are another characteristic that facilitates the apparent 2e-transfer (Scheme 1).…”

Section: Tricolor Electrochromism In the Uv/vis/nir Regioncontrasting

confidence: 65%

Double Dynamic Structural Change Enabling Tricolor Chromism by the Realization of Apparent Two‐Electron Transfer to Skip the Open‐Shell State

Harimoto

Sugai

Sugawara

et al. 2023

Chemistry A European J

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Most redox systems generally cannot avoid the involvement of open-shell species upon generating multiply charged species, which often reduces reversibility in multi-color electrochromic systems.In this study, we newly synthesized octakis(aminophenyl)-substituted pentacenebisquinodimethane (BQD) derivatives and their hybrids with alkoxyphenyl analogues. Thanks to apparent two-electron transfer accompanied by double dramatic changes in the structure of the arylated quinodimethane skeleton, the dicationic and tetracationic states were generated and isolated quantitatively because of the negligible steady-state concentration of intermediary open-shell species such as monocation or trication radicals. When two electrophores with different donating abilities are attached to the BQD skeleton, a dicationic state with a different color can be isolated in addition to the neutral and tetracationic states. For these tetracations, an interchromophore interaction induces a red-shift of the NIR absorptions, thus realizing tricolor UV/Vis/ NIR electrochromic behavior involving only closed-shell states.

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Section: Tricolor Electrochromism In the Uv/vis/nir Regioncontrasting

confidence: 65%

Double Dynamic Structural Change Enabling Tricolor Chromism by the Realization of Apparent Two‐Electron Transfer to Skip the Open‐Shell State

Harimoto

Sugai

Sugawara

et al. 2023

Chemistry A European J

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Structural‐Change‐Induced Two‐Stage Redox Behavior of Pentacenebisquinodimethane with Tricolor Chromism

Ishigaki,

Mizuno,

Harimoto

et al. 2024

Chemistry An Asian Journal

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Tricolor electrochromism was realized through the interconversion among the neutral (yellow), dicationic (green), and tetracationic (blue) states, even though only one kind of chromophore is generated upon oxidation. Both dicationic and tetracationic states were isolated as stable salts, and their different colors come from the effective interchromophore interaction only in the tetracationic state but not in the dicationic state. Despite the negligible Coulombic repulsion in the tetracationic state with four cyanine‐type chromophores, pentacenebisquinodimethane undergoes stepwise two‐stage two‐electron oxidation when radical‐stabilizing 5‐(4‐octyloxyphenyl)‐2‐thienyl groups are attached on the exomethylene bonds. A contribution from the biradical form only in the neutral state but not in the dicationic state is the reason for the observed negative cooperativity during the electrochemical oxidation.

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Recent Advances in NIR‐Switchable Multi‐Redox Systems Based on Organic Molecules

Harimoto,

Ishigaki

2024

Chemistry A European J

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In recent years, near‐infrared (NIR) dyes, exhibiting absorption in the NIR region (750‐2500 nm), have been applied to various optical applications such as security marking, photovoltaic cells and chemotherapy of deep tissues in vivo. Electrochromic systems capable of switching NIR absorption are attractive from the viewpoint of applications for material and life science, and thus several examples have been reported to date. The development of organic‐based materials is needed to reduce the environmental impact and improve biocompatibility, however, the switching of NIR absorption based on redox interconversion is still a challenging issue regarding reversibility and durability during interconversion. To overcome this potential instability, several studies on organic electrochromic systems that allow ON/OFF switching of NIR absorption have been developed in recent years. In this review, we focus on redox‐active well‐defined small molecules that enable ON/OFF switching of NIR absorption, and present recent studies on their intrinsic electrochemical and spectroscopic properties and/or structural characterization of their charged states. We also address more sophisticated electrochromic systems that can modulate their properties in response to external stimuli such as light, heat, and electric potential.

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Geometrical and Electronic Structure of Cation Radical Species of Tetraarylanthraquinodimethane: An Intermediate for Unique Electrochromic Behavior

Cited by 5 publications

References 32 publications

Double Dynamic Structural Change Enabling Tricolor Chromism by the Realization of Apparent Two‐Electron Transfer to Skip the Open‐Shell State

Double Dynamic Structural Change Enabling Tricolor Chromism by the Realization of Apparent Two‐Electron Transfer to Skip the Open‐Shell State

Structural‐Change‐Induced Two‐Stage Redox Behavior of Pentacenebisquinodimethane with Tricolor Chromism

Recent Advances in NIR‐Switchable Multi‐Redox Systems Based on Organic Molecules

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