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Communication | Regular issue | Vol 63, No. 4, 2004, pp.759-764
Published online, 6th February, 2004
DOI: 10.3987/COM-03-9977
Well-divided and pH-Dependent Bimodal Chemiluminescence of 2-Methyl-6-phenyl-8-(4-substituted phenyl)imidazo[1,2-a]pyrazin-3(7H)-ones Induced by Superoxide Anion

Ryota Saito,* Chizuru Inoue, and Akira Katoh

*Department of Applied Chemistry, Seikei University, Musashino, Tokyo 180-8633, Japan


An unprecedented pH-dependent bimodal chemiluminescence of 2-methyl-6-phenyl-8-(4-substituted phenyl)imidazo[1,2-a]pyrazin-3(7H)-ones (1a and 1b) initiated by superoxide anion (O2·-) in phosphate buffer solutions is described. The intensity ratio of the bimodal luminescence due to two light-emitting species, the singlet-excited neutral 2-acetamido-5-phenyl-3-(4-substituted phenyl)pyrazine [1(2a)* or 1(2b)*] and its amide anion [1(2a-)* or 1(2b-)*], varied as the pH rose. The percentage of the anionic luminescence intensity [Ianion/(Ineutral+Ianion)] for 1a showed a good linear correlation with the pH value, demonstrating the usefulness of 1a as a pH indicator as well as an O2·- probe.