Solvent Radical Anions in Irradiated Aliphatic Ketones and Esters as Observed Using Time-Resolved Magnetic Field Effects in the Recombination Fluorescence

Abstract

Abstract It has been found that addition of alcohols (~0.1 M) to some liquid ketones and esters results in well-pronounced oscillations in the decay of the delayed fluorescence intensity from irradiated solutions. The analysis of the time-resolved magnetic field effects (TR MFEs) in the recombination fluorescence has shown that these oscillations are a manifestation of singlet-triplet transitions in spin-correlated radical ion pairs (RIPs) created by irradiation. Comparison with literature data indicates that the transitions are due to hyperfine couplings (HFCs) in the solvent radical anion (RA), stabilized due to the presence of alcohol molecules. In acetone, this stabilization effect has been observed for methanol, ethanol, 2- propanol, and, to a smaller extent, for tert-butanol. Similar effects have also been observed in diethyl ketone, ethyl acetate, and methyl propionate but not in methyl tert-butyl ketone and ethyl trimethylacetate. The results obtained indicate that the interaction between the radical anions (RAs) of carbonyl compounds and alcohol molecules is of importance in pulse radiolysis studies of organic liquids and their mixtures.