Quenching of Aromatic Hydrocarbon Singlets and Aryl Ketone Triplets by Alkyl Disulfides

Quenching of aromatic hydrocarbon fluorescence and aryl ketone phosphorescence by alkyl disulfides has been investigated. Two quenching mechanisms, charge-transfer stabilized exciplex formation and electronic energy transfer, have been considered. Charge transfer appears to be unimportant for the aromatic hydrocarbons and ketones studied. Endothermic singlet-singlet energy transfer is more efficient than predicted by the Arrhenius equation. Excitation of vibrationally excited ground-state disulfide molecules provides a possible explanation for efficient endothermic quenching. Low-temperature uv spectroscopy indicates that the long-wavelength absorption of disulfides consists predominately of hot-band transitions.