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Short Paper | Regular issue | Vol 100, No. 10, 2020, pp.1666-1677
Published online, 3rd August, 2020
DOI: 10.3987/COM-20-14309
Change in the Fluorescence of 1,1′-Diaryl-2,2′-biimidazoles upon the Addition of Acid

Shoji Matsumoto,* Seigi Tachibana, and Motohiro Akazome

*Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan


The optical properties of a series of 1,1′-diaryl-2,2′-biimidazoles were examined. Different transitions were observed in their fluorescence spectra upon changing the electronic properties of the phenyl ring at the C1 and C1′ positions. The presence of a formyl group on the phenyl ring results in fluorescence via a CT transition with a solvent effect. A bathochromic change was observed when HCl was added to a solution of compound bearing a methoxy group in CH2Cl2, whereas a hypsochromic change was observed in compound bearing a formyl group. These observations were attributed to the protonation, which causes a characteristic change in their biimidazole moieties.