Synthesis and Characterization of Acetylene‐Linked Bisphenalenyl and Metallic‐Like Behavior in Its Charge‐Transfer Complex |
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Authors: | Takashi Kubo Prof Yuko Goto Mikio Uruichi Dr Kyuya Yakushi Prof Masayoshi Nakano Prof Akira Fuyuhiro Dr Yasushi Morita? Prof Kazuhiro Nakasuji Prof |
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Institution: | 1. Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama 1‐1, Toyonaka, Osaka 560‐0043, Japan, Fax: (+81)?6‐6850‐5387;2. Department of Applied Molecular Science, Institute for Molecular Science, Okazaki 444‐8585, Japan;3. Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, Machikaneyama 1‐3, Toyonaka, Osaka 560‐8531, Japan;4. PRESTO, Japan Science and Technology Agency (JST), Saitama 332‐0012, Japan |
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Abstract: | We prepared and isolated a phenalenyl‐based neutral hydrocarbon ( 1 b ) with a biradical index of 14 %, as well as its charge‐transfer (CT) complex 1 b –F4‐TCNQ. The crystal structure and the small HOMO–LUMO gap assessed by electrochemical and optical methods support the singlet‐biradical contribution to the ground state of the neutral 1 b . This biradical character suggests that 1 b has the electronic structure of phenalenyl radicals coupled weakly through an acetylene linker, that is, some independence of the two phenalenyl moieties. The monocationic species 1 b. + was obtained by reaction with the organic electron acceptor F4‐TCNQ. The cationic species has a small disproportionation energy ΔE for the reaction 2× 1 b. +? 1 b + 1 b 2+, which presumably originates from the independence of the phenalenyl moieties. The small ΔE led to a small on‐site Coulombic repulsion Ueff=0.61 eV in the CT complex. Moreover, a very effective orbital overlap of the phenalenyl rings between molecules afforded a relatively large transfer integral t=0.09 eV. The small Ueff/4t ratio (=1.7) resulted in a metallic‐like conductive behavior at around room temperature. Below 280 K, the CT complex showed a transition into a semiconductive state as a result of bond formation between phenalenyl and F4‐TCNQ carbon atoms. |
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Keywords: | acetylene charge transfer phenalenyl radical ions radicals |
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