Classification of select aceanthrylenes, acephenanthrylenes and dicyclopentapyrenes as alternant versus nonalternant polycyclic aromatic hydrocarbons on the basis of their fluorescence quenching behavior in the presence of nitromethane and cetylpyridinium cation selective quenching agents

Fluorescence behavior of dicyclopenta[cd, fg]pyrene, dicyclopenta[cd, jk]pyrene and dicyclopenta[cd, mn]pyrene is reported in the presence of nitromethane and cetylpyridinium (CPy+) cation quenching agents. Nitromethane and CPy+ are known to selectively quench fluorescence emission of alternant polycyclic aromatic hydrocarbons (PAHs). Emission intensities of nonalternant PAHs. with a few noted exceptions. are unaffected. Experimental measurements show that nitromethane and CPy+ effectively quenched fluorescence emission of the three dicyclopentapyrenes, thus suggesting that the perimeter C=C double bonds in the two cyclopenta-rings are alkenic, rather than aromatic in nature. Also reported are the fluorescence properties of 14 aceanthrylene and acrphenanthrylene derivatives, as well as several structurally related compounds, to further document the cetylpyridinium cation's quenching selectivity.