Quinoid-viologen conjugates: Redox properties and host-guest complex with cucurbiturils

Chen, Zhi Yuan; Khoo, Rebecca Shu Hui; Garzón‐Ruiz, Andrés; Yang, Chen; Anderson, Christopher L.; Navarro, Amparo; Zhang, X.; Zhang, J.; Lv, Yongqin; Liu, Yi

doi:10.1016/j.mtchem.2022.100933

Cited by 2 publications

(3 citation statements)

References 53 publications

(86 reference statements)

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“…They not only function as strong redox-active acceptor units but also show interesting host−guest interactions with hosts such as cucurbiturils (CBs), thanks to the unique viologen−quinoid construct. 35 The strong electron-accepting properties of iAQMs have been harnessed to create ionic, ultranarrow band gap conjugated polymers, such as P13 and P14, that contain triphenylphosphonium-appended iAQMs and terthiophene and quaterthiophene groups in their respective repeat units. These conjugated polyelectrolytes (CPEs) showcase the band gap reduction effects of combining the donor−acceptor strategy with the quinoid-modulated bond-length alternation reduction strategy.…”

Section: Strongly Electron-withdrawing Ionic Aqms and Conjugated Poly...mentioning

confidence: 99%

“…Moreover, novel viologen conjugated iAQMs have been constructed following a similar protocol. They not only function as strong redox-active acceptor units but also show interesting host–guest interactions with hosts such as cucurbiturils (CBs), thanks to the unique viologen–quinoid construct …”

Section: Modulating the Electronic Properties And Reactivity Of Aqmsmentioning

confidence: 99%

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p-Azaquinodimethane: A Versatile Quinoidal Moiety for Functional Materials Discovery

2023

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Conspectus The past 50 years of discovery in organic electronics have been driven in large part by the donor–acceptor design principle, wherein electron-rich and electron-poor units are assembled in conjugation with each other to produce small band gap materials. While the utility of this design strategy is undoubtable, it has been largely exhausted as a frontier of new avenues to produce and tune novel functional materials to meet the needs of the ever-increasing world of organic electronics applications. Its sister strategy of joining quinoidal and aromatic groups in conjugation has, by comparison, received much less attention, to a great extent due to the categorically poor stability of quinoidal conjugated motifs. In 2017 though, the p-azaquinodimethane (AQM) motif was first unveiled, which showed a remarkable level of stability despite being a close structural analogue to p-quinodimethane, a notably reactive compound. In contrast, dialkoxy AQM small molecules and polymers are stable even under harsh conditions and could thus be incorporated into conjugated polymers. When polymerized with aromatic subunits, these AQM-based polymers show notably reduced band gaps that follow reversed structure–property trends to some of their donor–acceptor polymer counterparts and yield organic field-effect transistor (OFET) hole mobilities above 5 cm2 V–1 s–1. Additionally, in an ongoing study, these AQM-based compounds are also showing promise as singlet fission (SF) active materials due to their mild diradicaloid character. An expanded world of AQMs was accessed through their ditriflate derivatives, which were first used to produce ionic AQMs (iAQMs) sporting two directly attached cationic groups that significantly affect the AQM motif’s electronics, producing strongly electron-withdrawing quinoidal building blocks. Conjugated polyelectrolytes (CPEs) created with these iAQM building blocks exhibit optical band gaps stretching into the near-infrared I (NIR-I) region and showed exemplary behavior as photothermal therapy agents. In contrast to these stable AQM examples, the synthetic exploration of AQMs also produced examples of more typical diradicaloid reactivity but in forms that were controllable and produced intriguing and high-value products. With certain substitution patterns, AQMs were found to dimerize to form highly substituted [2.2]paracyclophanes in distinctly more appreciable yields than typical cyclophane formation reactions. Certain AQM ditriflates, when crystallized, undergo light-induced topochemical polymerization to form ultrahigh molecular weight (>106 Da) polymers that showed excellent performances as dielectric energy storage materials. These same AQM ditriflates could be used to produce the strongly electron-donating redox-active pentacyclic structure: pyrazino[2,3-b:5,6-b′]diindolizine (PDIz). The PDIz motif allowed for the synthesis of exceedingly small band gap (0.7 eV) polymers with absorbances reaching all the way into the NIR-II region that were also found to produce strong photothermal effects...

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Section: Strongly Electron-withdrawing Ionic Aqms and Conjugated Poly...mentioning

confidence: 99%

Section: Modulating the Electronic Properties And Reactivity Of Aqmsmentioning

confidence: 99%

p-Azaquinodimethane: A Versatile Quinoidal Moiety for Functional Materials Discovery

2023

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“…Due to the high stability, this moiety has been connected with various aromatic subunits and developed several small molecules and polymers (Chart ). − The developed compounds have been found to show notably reduced band gaps and high carrier mobility and singlet fission characteristics. Interestingly, none of the compounds have been reported to be fluorescent.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of p-Azaquinodimethane-based Quinoidal Fluorophores

2023

J. Org. Chem.

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Quinoidal π-conjugated systems are sought-after materials for semiconducting applications because of their rich optical and electronic characteristics. However, the analogous fluorescent compounds are extremely rare, with just two reports in the literature. Here, we present the design and development of a third series of quinoidal fluorophores [(2,5-diarylidene)-3,6-bis(hexyloxy)-2,5-dihydropyrazine (Q1–Q5)] that incorporates p-azaquinodimethane. The fluorophores are synthesized in a two-step synthetic approach employing Knoevenagel condensation of N,N-diacetyl-piperazine-2,5-dione with different aromatic aldehydes followed by O-alkylation in high yields. Q1–Q5 are strongly emissive, and by altering the aryl-substituents, the emission colors can be modulated from blue to orange. The compounds possess emission maxima (λem) at 475–555 nm in the solution state and 510–610 nm in the solid state, with fluorescence quantum yields of up to 60%. To the best of our knowledge, the reported systems are the first quinoidal dual-state emissive (solution- and solid-state) compounds. In trifluoroacetic acid, Q5 exhibits halochromic behavior, with a dramatic color change from yellow to blue. Furthermore, the preliminary fluorescent sensing studies demonstrated that Q5 could act as a selective turn-off fluorescence probe for electron-deficient picric acid (PA), with an emission quenching of >90% in the solution state. The thin-layer chromatography (TLC) strip sensor of Q5 was also designed to detect PA in water.

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Quinoid-viologen conjugates: Redox properties and host-guest complex with cucurbiturils

Cited by 2 publications

References 53 publications

p-Azaquinodimethane: A Versatile Quinoidal Moiety for Functional Materials Discovery

p-Azaquinodimethane: A Versatile Quinoidal Moiety for Functional Materials Discovery

Synthesis of p-Azaquinodimethane-based Quinoidal Fluorophores

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