- Rethinking Uncaging: A New Antiaromatic Photocage Driven by a Gain of Resonance Energy
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Photoactivatable compounds for example photoswitches or photolabile protecting groups (PPGs, photocages) for spatiotemporal light control, play a crucial role in different areas of research. For each application, parameters such as the absorption spectrum, solubility in the respective media and/or photochemical quantum yields for several competing processes need to be optimized. The design of new photochemical tools therefore remains an important task. In this study, we exploited the concept of excited-state-aromaticity, first described by N. Colin Baird in 1971, to investigate a new class of photocages, based on cyclic, ground-state-antiaromatic systems. Several thio- and nitrogen-functionalized compounds were synthesized, photochemically characterized and further optimized, supported by quantum chemical calculations. After choosing the optimal scaffold, which shows an excellent uncaging quantum yield of 28 %, we achieved a bathochromic shift of over 100 nm, resulting in a robust, well accessible, visible light absorbing, compact new photocage with a clean photoreaction and a high quantum product (??Φ) of 893 M?1 cm?1 at 405 nm.
- Hermanns, Volker,Scheurer, Maximilian,Kersten, Nils Frederik,Abdellaoui, Chahinez,Wachtveitl, Josef,Dreuw, Andreas,Heckel, Alexander
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supporting information
p. 14121 - 14127
(2021/09/03)
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- Bithiophene-fused benzo[c]phospholes: Novel P,S-containing hybrid π-conjugated systems with small HOMO-LUMO energy gaps
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Bithiophene-fused benzo[c]phospholes were successfully prepared by a TiII-mediated cyclization of dialkynylated bithiophene derivatives. It was revealed that the optical and electrochemical properties of the bithiophene-fused benzo[c]phospholes are deeply related to the π-conjugation modes at the fused bithiophene subunits. Both experimental and theoretical results demonstrate that the appropriately ringannulated systems are potential emitters with small HOMOLUMO energy gaps covering the orange-to-red region due to the efficient π-electron derealization over the three conjugated heterole rings. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Miyajima, Tooru,Matano, Yoshihiro,Imahori, Hiroshi
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p. 255 - 259
(2008/09/18)
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- Efficient construction of biaryls and macrocyclic cyclophanes via electron-transfer oxidation of Lipshutz cuprates
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An efficient method for the homocoupling of aryl halides by electron-transfer oxidation of Lipshutz cuprates (Ar2Cu(CN)Li 2) with organic electron acceptors is disclosed. Thus, various types of Lipshutz cuprates are prepared by successive treatment of aryl or heteroaryl bromides with tert-butyllithium and CuCN. The electron-transfer oxidation of Lipshutz cuprates with p-benzoquinones proceeds smoothly to afford the corresponding homocoupling products in moderate to good yields. Furthermore, it can be applied to the construction of either thiophene- or benzene-fused 10-membered ring cyclophanes. For the synthesis of 10-membered cyclophanes, the linear C-Cu-C structure of Lipshutz cuprates should be maintained in the dimetallacyclic intermediates, producing the large ring cyclophanes efficiently. The X-ray analysis of the cyclophanes reveals that the difference in the bridging atoms results in the different conformations of the macrocyclic rings. Thus, the silicon-bridged cyclophane 5a adopts a D2-symmetric structure with a twisted rhombic arrangement of four thiophene rings, whereas the methylene- and oxygen-bridged cyclophanes 5b and 5c possess C2h- and C2-symmetric structures with chair- and boatlike conformations, respectively. The 1H NMR spectrum of C2-symmetric 5c is temperature-dependent, and the activation energy (ΔG?) for the conformational change is 10.1 kcal/mol.
- Miyake, Yoshihiro,Wu, Mo,Rahman, M. Jalilur,Kuwatani, Yoshiyuki,Iyoda, Masahiko
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p. 6110 - 6117
(2007/10/03)
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- Novel electron-transfer oxidation of Lipshutz cuprates with 1,4-benzoquinones: An efficient homo-coupling reaction of aryl halides and its application to the construction of macrocyclic systems
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The electron transfer reaction from Lipshutz cuprates, which can be easily prepared from aryl bromides, to 1,4-benzoquinones was found to proceed smoothly, affording either the corresponding homo-coupling products, in modest to excellent yields, or macrocyclic products selectively.
- Miyake, Yoshihiro,Wu, Mo,Rahman, M. Jalilur,Iyoda, Masahiko
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p. 411 - 413
(2007/10/03)
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- Helically annelated and cross-conjugated oligothiophenes: Asymmetric synthesis, resolution, and characterization of a carbon-sulfur [7]helicene
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The synthesis and characterization of a novel oligothiophene, in which the thiophene rings are annelated into a [7]helicene with cross-conjugated π-system, are described. Such [7]helicenes may be viewed as fragments of the unprecedented carbon-sulfur (Cs
- Rajca, Andrzej,Miyasaka, Makoto,Pink, Maren,Wang, Hua,Rajca, Suchada
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p. 15211 - 15222
(2007/10/03)
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- New syntheses of tricyclic thiophenes and cyclic tetrathiophenes using transition-metal-catalyzed cyclization
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New synthetic methods for polycyclic thiophenes were developed. Thus, dithienothiophenes, cyclopentadithiophene, silacyclopentadithiophenes, and cyclooctatetrathiophenes were synthesized in moderate to good yields by using the CuCl2-mediated cyclization of organocopper(I) and organozinc intermediates prepared from dilithio-derivatives with CuCN or ZnCl2, respectively. A direct cyclization of bromothiophene derivatives with hexamethylditin in the presence of tetrakis(triphenylphosphine)palladium(0) also gave dithienothiophenes, cyclopenta-dithiophenes, and silacyclopentadithiophenes in good yields.
- Kabir, S. M. Humayun,Miura, Mami,Sasaki, Shigeru,Harada, Genta,Kuwatani, Yoshiyuki,Yoshida, Masato,Iyoda, Masahiko
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p. 761 - 774
(2007/10/03)
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- Synthesis of biaryls using the coupling reaction of diaryldimethyltins with copper(II) nitrate
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The coupling of diaryldimethyltins with Cu(NO3)2·3H2O in THF proceeds smoothly at room temperature under ambient atmosphere to produce the corresponding biaryls in good to high yields. Diaryldimethyltins can be prepared in high yields by the reaction of aryllithiums with dichlorodimethyltin.
- Harada, Genta,Yoshida, Masato,Iyoda, Masahiko
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p. 160 - 161
(2007/10/03)
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