- Visible-Light-Induced Heptacene Generation under Ambient Conditions: Utilization of Single-crystal Interior as an Isolated Reaction Site
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The photo-induced generation of unstable molecules generally requires stringent conditions to prevent oxidation and the concomitant decomposition of the products. The visible-light-induced conversion of two heptacene precursors to heptacene was studied. Single crystals of bis- and mono-α-diketone-type heptacene precursors (7-DK2 and 7-DK1, respectively), were prepared to investigate the effect of precursor structure on reactivity. The photoirradiation of a 7-DK2 single crystal cleaved only one α-diketone group, forming an intermediate bearing a pentacene subunit, while that of a 7-DK1 single crystal gave rise to characteristic absorption peaks of heptacene and their increase in intensity with photoirradiation time, indicating the generation of heptacene without decomposition. Heptacene production was not observed when the precursors were photoirradiated in solution, implying that the single crystal interior provided isolation from the external environment, thus preventing heptacene oxidation.
- Hayashi, Hironobu,Hieda, Nao,Yamauchi, Mitsuaki,Chan, Yee Seng,Aratani, Naoki,Masuo, Sadahiro,Yamada, Hiroko
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- Heptacene: Characterization in Solution, in the Solid State, and in Films
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Acenes comprise an important class of organic semiconducting materials. As graphene nanoribbons of ultimate width, they are valuable atom-precise model systems for studying the properties of this form of nanoscale carbon materials. Heptacene is the smallest member of the acene series that could only be studied under matrix isolation conditions. Its existence in bulk had never been positively confirmed, despite efforts dating back more than 70 years. We report that the reduction of 7,16-heptacenequinone produces a mixture of two diheptacene molecules. The diheptacenes undergo thermal cleavage to heptacene at high temperatures in the solid state. Monitoring this cycloreversion by solid state 13C cross-polarized magic angle spinning NMR reveals that solid heptacene has a half-life time of several weeks at room temperature. The diheptacenes are valuable precursors for generating films of heptacene by vapor phase deposition that can be studied below or at room temperature.
- Einholz, Ralf,Fang, Treliant,Berger, Robert,Grüninger, Peter,Früh, Andreas,Chassé, Thomas,Fink, Reinhold F.,Bettinger, Holger F.
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- Stable photoinduced charge separation in heptacene
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Heptacene, generated in inert gas matrices by photobisdecarbonylation of a bridged α-diketone precursor, undergoes ionization into radical anion and radical cation upon UV irradiation. The Royal Society of Chemistry.
- Bettinger, Holger F.,Mondal, Rajib,Neckers, Douglas C.
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- Heptacene: Synthesis and Its Hole-Transfer Property in Stable Thin Films
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Heptacene (1) has been produced via a monoketone precursor, 2, which was prepared from 1,2,4,5-tetrabromobenzene in nine steps in a total yield of 10 %. Compound 2 was converted to 1 quantitatively by heating at 202 °C. Heptacene exhibited high thermal stability in the solid state without any observable change over two months. To investigate the potential value of 1 as a material for p-type organic field-effect transistors (OFETs), top-contact OFET devices were fabricated by vacuum deposition of 1 onto a hexamethyldisilazane (HMDS)/SiO2/Si substrate. The best hole mobility performance was 2.2 cm2 V?1 s?1. This is the first report of stable heptacene being used in an effective device and examined for its charge carrier properties.
- Miyazaki, Takaaki,Watanabe, Motonori,Matsushima, Toshinori,Chien, Ching-Ting,Adachi, Chihaya,Sun, Shih-Sheng,Furuta, Hiroyuki,Chow, Tahsin J.
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- A Practical General Method for the Preparation of Long Acenes
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The field of long acenes, the narrowest of the zig-zag graphene nanoribbons, has been an area of significant interest in the past decade because of its potential applications in organic electronics, spintronics and plasmonics. However the low solubility and high reactivity of these compounds has so far hindered their preparation on large scales. We report here a concise strategy for the synthesis of higher acenes through Diels–Alder condensation of arynes with a protected tetraene ketone. After deprotection by cleavage of the ketal, the obtained monoketone precursors cleanly yield the corresponding acenes through quantitative cheletropic thermal decarbonylation in the solid state, at moderate temperatures of 155 to 205 °C. This approach allows the preparation of heptacene, benzo[a]hexacene, cis- and trans-dibenzopentacene and offers a valuable new method for the synthesis of even larger acenes.
- Jancarik, Andrej,Levet, Gaspard,Gourdon, André
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p. 2366 - 2374
(2019/01/24)
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- Higher Acenes by On-Surface Dehydrogenation: From Heptacene to Undecacene
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A unified approach to the synthesis of the series of higher acenes up to previously unreported undecacene has been developed through the on-surface dehydrogenation of partially saturated precursors. These molecules could be converted into the parent acenes by both atomic manipulation with the tip of a scanning tunneling and atomic force microscope (STM/AFM) as well as by on-surface annealing. The structure of the generated acenes has been visualized by high-resolution non-contact AFM imaging and the evolution of the transport gap with the increase of the number of fused benzene rings has been determined on the basis of scanning tunneling spectroscopy (STS) measurements.
- Zuzak, Rafal,Dorel, Ruth,Kolmer, Marek,Szymonski, Marek,Godlewski, Szymon,Echavarren, Antonio M.
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p. 10500 - 10505
(2018/08/17)
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- Synthesis, stability, and photochemistry of pentacene, hexacene, and heptacene: A matrix isolation study
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The photochemical bisdecarbonylation of bridged α-diketones (Strating-Zwanenburg reaction) to give the oligoacenes pentacene (2), hexacene (3), and heptacene (4) is investigated in solid inert gas matrices at cryogenic temperatures. The photodecomposition
- Mondal, Rajib,Toenshoff, Christina,Khon, Dmitriy,Neckers, Douglas C.,Bettinger, Holger F.
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experimental part
p. 14281 - 14289
(2010/02/16)
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- Photogeneration of heptacene in a polymer matrix
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Heptacene (1) was generated by the photodecarbonylation of 7,16-dihydro-7,16-ethanoheptacene-19,20-dione (2) in a polymer matrix using a UV-LED lamp (395 ± 25 nm). Compound 1 showed a long wavelength absorption band extending from 600 to 825 nm (λmax ~760 nm) and was found to be stable up to 4 h in the polymer matrix. However, irradiation of a solution of 2 in toluene produced only oxygen adducts. Copyright
- Mondai, Rajib,Shah, Bipin K.,Neckers, Douglas C.
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p. 9612 - 9613
(2007/10/03)
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