Classification of select aceanthrylenes, acephenanthrylenes and dicyclopentapyrenes as alternant versus nonalternant polycyclic aromatic hydrocarbonson 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]py rene and dicyclopenta[cd, mn]pyrene is reported in the presence of nitromet hane and cetylpyridinium (CPy+) cation quenching agents. Nitromethane and C Py+ are known to selectively quench fluorescence emission of alternant poly cyclic aromatic hydrocarbons (PAHs). Emission intensities of nonalternant P AHs. 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 d ouble bonds in the two cyclopenta-rings are alkenic, rather than aromatic i n 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 sele ctivity.