Spectroscopic Properties of Polycyclic Aromatic Compounds. Part 5. The Nitromethane Selective Quenching Rule Revisited in Aqueous Micellar Solvent Media

Abstract

Applicability of the nitromethane selective quenching rule for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for 40 representative PAH solutes dissolved in micellar tetradecyltrimethylammonium bromide (TTAB) and micellar sodium dodecanoate (SDD) solvent media. Experimental results show that nitromethane quenched flourescence emission of only the 19 alternant PAHs in the cationic (TTAB) solvent media as expected. Emission intensities of nonalternant PAHs, except for dibenzo[b,k]flouranthene,dibenz[a,e]acephenanthrylene and two exceptions noted previously, were unaffected by nitromethane addition. Unexpected quenching behavior was observed, however, in the case of nonalternant PAHs dissolved in micellar sodium dodecanoate solvent media. Nitromethane quenched fluorescence emission of nonalternant PAHs studied in the SDD solvent media, which is contrary to the selective quenching rule.