65Poster Award NomineeP3-05Synthesis and Characterization of Oligoacenes Hironobu Hayashi1 and Hiroko Yamada2 1 Center for Basic Research on Materials, National Institute for Materials Science (NIMS) 2 Institute for Chemical Research (ICR), Kyoto University Oligoacenes are an important class of polycyclic aromatic hydrocarbons that have recently gained exceptional attention as promising materials for organic electronic devices. The nature of the ground state of oligoacenes has been widely debated so far, and remains controversial. One of the main reasons is the difficulty in synthesizing oligomacenes because of their low solubility and stability. To address thes issues, in this study, we utilize “thermal and photochemical precursor methods”. Briefly, bicyclo[2.2.2]octadiene(BCOD)-fused oligoacenes can be converted to the corresponding oligoacenes by the thermally induced retro-Diels-Alder reactions, while a-diketone-type precursors can be converted simply by photoirradiation. Here, we report the synthesis of oligoacene precursors and their on-surface conversion to oligoacenes on Au(111) under ultra-high vacuum conditions. For example, we demonstrate the on-surface generation of nonacene via visible-light-induced photodecarbonylation of a-diketone-type precursors. STM and nc-AFM analyses unambiguously confirmed the chemical structure. In addition, STS measurements coupled with theoretical calculations indicated the open-shell character of nonacene.[1] [1] J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. D. Giovannantonio, R. Widmer, M. Yamashita, N. Hieda, P. Ruffieux, H. Yamada, R. Fasel, Nat. Commun., 10, 861 (2019). P3-06On-surface Synthesis of Azobenzene-linked PorphyrinY. Isshiki1, D. Li1, S. Vijayaraghavan2, K. Sun1, T. H. Ngo3, Y. Matsushita4, E. A. Neal3, J. P. Hill3,and S. Kawai1,51 Center for Basic Research on Materials, National Institute for Materials Science (NIMS)2 CSIR-Central Electrochemical Research Institute3 Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS)4 Research Network and Facility Services Division, National Institute for Materials Science (NIMS)5 Graduate School of Pure and Applied Sciences, University of TsukubaPorphyrins are useful materials in the fields of photonics and organic electronics [1]. In this study, azobenzene-linked porphyrins were synthesized on Au(111) surface from Pt porphyrin with tri-Methyl (tMe-Por) and tert-Butyl (tBu-Por) via diazo coupling reaction between nitro groups. Scanning tunneling spectroscopy revealed that tMe-Por forms self-assembled structures with different chirality molecules, while tBu-Por involves same chirality. Azobenzene-linked porphyrins with mixed chirality were formed after annealing for both precursors, with a significantly higher yield from tMe-Por, indicating that its assembly with different chiralities Figure: dI/dV mapping of tBu-Por at the bias of promotes diazo coupling more efficiently. We clarified that the diazo coupling in tBu-Por goes through multiple -1.2 V before and after annealing.reaction steps by the change of chirality.[1] J. Chen, et al., Angew. Chem. Int. Ed., 60, 5010-5035 (2021).
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