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