Protonation-induced cyclization of 1,8-bis(arylethynyl)anthraquinones: Monopyrylium salt formation and intensification of donor-acceptor interaction

Koya Prabhakara Rao, Mio Kondo, Ryota Sakamoto, Tetsuro Kusamoto, Shoko Kume, Hiroshi Nishihara

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9 Citations (Scopus)

Abstract

We previously reported protonation-induced double cyclization reaction of 1,4-Ar2Aq and 1,5-Ar2Aq (Ar2Aq: bis(arylethynyl) anthraquinone) with strong acid HX that generated the corresponding dipyrylium salts [1,4-Ar2Pyl2]X2 and [1,5-Ar2Pyl2]X2. In this communication we disclose the protonation reactions of 1,8-Fc2Aq (Fc: ferrocenyl), 1,8-Am2Aq (Am: 4-N,N-bis(4-methoxyphenyl)aminophenyl), and 1,8-AmFcAq, which is the first example of heterodonor molecules in the Ar 2Aq series, and synthesized by means of stepwise SonogashiraHagihara cross-coupling reactions. In contrast to the 1,4-Ar2Aq and 1,5-Ar2Aq series, 1,8-Ar2Aq undergoes protonation-induced single cyclization, so that it is converted into the corresponding monopyrylium salt [1,8-Ar2Pyl]X. [1,8-Ar2Pyl]X features an extremely small HOMOLUMO gap (0.50-0.73 V), ascribable to the significant lowering of the LUMO level upon the pyrylium formation.

Original languageEnglish
Pages (from-to)1456-1458
Number of pages3
JournalChemistry Letters
Volume40
Issue number12
DOIs
Publication statusPublished - 2011

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