Effect that Various Electron Donating Functional Groups have Regarding Nitromethane's Inability to Quench Fluorescence Emission of Nonalternant Fluoranthenoid Polycyclic Aromatic Hydrocarbons

Abstract

Nitromethane selectively quenches fluorescence emission of alternant polycyclic aromatic hydrocarbons (PAHs) via an electron transfer mechanism. Emission intensities of nonalternant PAHs, for the most part, are unaffected. To better understand the quenching mechanism, the fluorescence behavoir of 1-methylfluoranthene, 2-methylfluoranthene, 3-methylfluoranthene, 7-methylfluoranthene, 8-methylfluoranthene, t-butyldibenzo[ghi, mno]fluoranthene, 10-methylbenzo[b]fluoranthene, 12-methoxybenzo[b]fluoranthene, 10-methoxybenzo[b]fluoranthene, 10-hydroxybenzo[b]fluoranthene, 10-hydroxybenzo[j]fluoranthene, 10-methoxybenzo[j]fluoranthene, 3-metnoxybenzo[k]fluoranthene, 3-hydroxy-benzo[k]fluoranthene, 9-methoxybenzo[k]fluoranthene and 9-hydroxybenzo[k]fluoranthene dissolved in neat acetonitrile, toluene-acetonitrile and ethyl acetate-acetonitrile solvents was measured at different nitromethane concentrations. Experimental results show that electron donating methyl-, t-butyl, methoxy- and hydroxy-groups do not favorably alter the molecular orbital energies and/or reduction potentials so as to encourage electron transfer from the substituted nonalternant PAH molecule to nitromethane, which acts as the electron acceptor in the presumed quenching mechanism.