| Research Abstract |
Followings are the main results of experimental studies with the time-resolved microwave dielectric absorption method combined with laser flash photolysis :
1. For N, N, N', N'-tetramethyl-p-phenylenediamine and N, N, N', N'-tetramethyl-benzidine in the presence of halogen-containing compounds, long-lived contact-ion-pairs are formed efficiently, and the efficiency and mechanism of their formation cannot be reconciled with those of the conventional electron-transfer processes, but correlate well to the electron attachment ptocesses in the gas phase. These results have been confirmed by the ordinary time-resolved light-absorption measurements following to flash photolysis.
Dipole moments of excited triplet states have been determined for aniline, its N-substituted derivatives (dimethylaniline, diethylaniline, diphenylamine, and triphenylamine) and ring-substituted compounds (o-, m-, p-anisidine, p-chloro-, p-nitro-, and p-cyano-aniline). Values obtained by the semi-empirical calculations are generally in good agreement with the present experimental ones.
Species with dipole moments much larger than those for the excited triplet states are formed for dimethylaniline and diethylaniline dissolved in carbontetrachloride. They can be ascribed to formation of contact ion pairs as in aromatic diamines.
It has been shown that photolysis of benzil at 308 nm laser pulse, in contrast to 355 nm photolysis, caused dissociation of the molecule into benzoyl radicals with the quantum yield of about 0.3, and the rest leads to the formation of the excited triplet state of benzil.
It has been suggested that determination of the dipole moment of excited state at very low temperatures may need further improvement of the detection sensitivity as well as the method of calibration of the signal intensity.
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