Recent Progress in Quinoidal Singlet Biradical Molecules

Kubo, Takashi

doi:10.1246/cl.140997

Cited by 271 publications

(163 citation statements)

References 98 publications

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“…Furthermore, in 2010, direct growth of structurally perfect GNRs was achieved on metal surfaces under ultrahigh vacuum (UHV) conditions. The syntheses and derivatizations of openshell graphene molecules, 23,46,[49][50][51][52][53] contorted PAHs, 20 fullerene fragments, 54-57 acenes, 46,58-61 rylenes, 62,63 helicenes, [64][65][66][67][68] and truxenes 69,70 have been extensively reviewed very recently and are therefore not included in this article. This complementary synthetic protocol under UHV conditions enabled the synthesis and direct characterization of unprecedented GNR structures that have been unattainable through solution synthesis, including nitrogen-doped GNRs.…”

Section: Introductionmentioning

confidence: 99%

New advances in nanographene chemistry

et al. 2015

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Nanographenes, or extended polycyclic aromatic hydrocarbons, have been attracting renewed and more widespread attention since the first experimental demonstration of graphene in 2004. However, the atomically precise fabrication of nanographenes has thus far been achieved only through synthetic organic chemistry. The precise synthesis of quasi-zero-dimensional nanographenes, i.e. graphene molecules, has witnessed rapid developments over the past few years, and these developments can be summarized in four categories: (1) non-conventional methods, (2) structures incorporating seven- or eight-membered rings, (3) selective heteroatom doping, and (4) direct edge functionalization. On the other hand, one-dimensional extension of the graphene molecules leads to the formation of graphene nanoribbons (GNRs) with high aspect ratios. The synthesis of structurally well-defined GNRs has been achieved by extending nanographene synthesis to longitudinally extended polymeric systems. Access to GNRs thus becomes possible through the solution-mediated or surface-assisted cyclodehydrogenation, or "graphitization," of tailor-made polyphenylene precursors. In this review, we describe recent progress in the "bottom-up" chemical syntheses of structurally well-defined nanographenes, namely graphene molecules and GNRs.

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Section: Introductionmentioning

confidence: 99%

New advances in nanographene chemistry

et al. 2015

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“…[1][2][3] Recently,w e have reported structural and electronic properties of at riarylamine having two 2,6-di-tert-butylphenoxy radical on the central nitrogen atom (1). [1][2][3] Recently,w e have reported structural and electronic properties of at riarylamine having two 2,6-di-tert-butylphenoxy radical on the central nitrogen atom (1).…”

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confidence: 99%

Modulation of Open‐shell Characters of Amine‐inserted Diphenoquinones via Structural Modification

Matsuta

Sakamaki

Kurata

et al. 2017

Chemistry An Asian Journal

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In this study, a series of triphenylamine derivatives with two 2,6-diphenylphenoxy radicals (2 a-d), which could be regarded as amine-inserted diphenoquinones have been synthesized and investigated their structures and electronic properties. The structures of 2 a-d were confirmed by single-crystal X-ray analysis, showing the characteristic bond length alternation patterns for closed-shell quinoids. The solutions of 2 a-d exhibited clear ESR signals even at room temperature, indicating their thermally accessible diradical states. The NMR and ESR measurements showed that the diradical character of 2 a-d were increased in the order of 2 a<2 b<2 c<2 d, well-reproduced by theoretical calculations. The results of this work strongly suggest that the diradical character of this class of compounds could be tuned by changing the substituent on the central nitrogen atom.

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“…Figure S2 in the Supporting Information). [25] Electrochemical properties On the other hand, the empirical molecular structures of 1-4 show clear bond length alternation (BLA) at the acenedithiophenedione cores (FiguresS3a nd S4 in the Supporting Information),s upporting the presence of quinoidal conjugation as expected.…”

Section: Single-crystal X-ray Analysismentioning

confidence: 99%

Dithienyl Acenedithiophenediones as New π‐Extended Quinoidal Cores: Synthesis and Properties

Kawabata

Osaka

Sawamoto

et al. 2017

Chemistry A European J

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We have synthesized two isomeric pairs of benzo- and naphthodithiophenediones with two flanking thiophenes and characterized them by single-crystal X-ray analysis, cyclic voltammetry, steady-state optical electronic absorption and emission spectroscopies, transient absorption spectroscopy, and vibrational spectroscopies with in situ spectroelectrochemistry techniques, and then compared them with the thieno[3,2-b]thiophene-2,5-dione counterpart that we previously reported. The results show that the central acenedithiophenedione cores have quinoidal conjugation with closed-shell character. The π-extension of the quinoidal core raises (lowers) the HOMO (LUMO) energy levels of the triads, resulting in the drastic reduction of their energy gaps from approximately 2.0 eV to 1.1 eV. Owing to the electron-withdrawing nature of the carbonyl terminal group at the quinoidal core, the triads have low-lying LUMO energy levels ranging from -3.9 eV to -4.3 eV, and can be regarded as strong electron-acceptor building units. Interestingly, the pairs of structural isomers have similar electronic structures in both the neutral and charged states despite the different shapes (linear and angular) and/or symmetry (C and C ) of the acenedithiophenedione cores.

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Recent Progress in Quinoidal Singlet Biradical Molecules

Cited by 271 publications

References 98 publications

New advances in nanographene chemistry

New advances in nanographene chemistry

Modulation of Open‐shell Characters of Amine‐inserted Diphenoquinones via Structural Modification

Dithienyl Acenedithiophenediones as New π‐Extended Quinoidal Cores: Synthesis and Properties

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