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Development of a structurally well-defined small molecule with a high oxygen reduction reaction catalytic activity is a key approach for the bottom-up design of a metal-free carbonbased catalysts for metal-air batteries and fuel cells. In this paper, we characterize the oxygen reduction reaction activities of trioxotriangulene derivatives, which are stable neutral radicals with high redox abilities, via rotating disk electrode measurements in alkaline aqueous solution. Among trioxotriangulene derivatives having various substituent groups, N-piperidinyl-substituted derivative mixed with acetylene black shows a high catalytic activity with the two-electron transferring process exceeding other derivatives and quinones. To reveal the correlation between molecular structure and catalytic activity, we discuss substituent effects on the redox ability of trioxotriangulene derivatives, and demonstrate that a molecule with electron-donating groups yields relatively higher catalytic activities.

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The molecular structures of I-phenyl-(5) and 1-(2-naphthyl)-8-tropyIionaphthalene (6) hexafluoroantimonates were determined by x-ray crystallography and compared with those of I,%-diphenylnaphthalene and related compounds. In these compounds, the two aromatic substituents face each other in a nearly parallel conformation with a splayed-out arrangement. In the cations 5 and 6, the distance between the facing rings is appreciably shorter than that of other 1,8-diarylnaphthalenes, suggesting the presence of some attractive force. This attraction is ascribed to an intramolecular charge-transfer interaction, and seems to bring about a slight inward bending of the 2-naphthyl substituent in the cation 6. AM1 calculations were carried out for these cations and the results are discussed in comparison with the results of x-ray crystallography.