Effects of Solute-Solvent Interactions on Radiationless Decay of Thioketones Excited to Their S2- and T1-States |
| M. Szymański, M. Balicki, M. Binkowski, J. Kubicki, A. Maciejewskia, E. Pawłowska and T. Wróżowa Institute of Physics and Faculty of Chemistrya, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań, Poland |
| Received: August 21, 1995; revised version: January 24, 1996 |
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| Spectral and photophysical properties of a few aromatic thioketones in their S2- and T1-states, in particular those determined by their interactions with solvents, are discussed. The reasons for a drastically different behaviour of thioketones in interactions with benzene as well as saturated hydrocarbons and perfluoroalkanes are analysed in more detail. Results of the time-resolved transient absorption measurements in the pico- and nanosecond time scale are given. An analysis of these results proves that a product of the decay of the S2-state of xanthione in benzene is a new transient (τ1/e ≥ 60 ps) individuum which, regarding the system properties and the conditions of the experiment, has been identified as an exciplex in S2-state formed as a result of an efficient interaction with benzene molecule. Also in xanthione//alkane systems the involvement of a transient individuum was proved. Most probably, this individuum was a thioketyl radical which could be formed by hydrogen abstraction from a hydrocarbon molecule by xanthione in the S2-state. Such individua act as intermediates in passing excitation to the triplet states of thioketones and are effective channels of the S2-state decay. The changes observed in the transient absorption spectra of xanthione in C6H6 in the time range of 10-7-10-6 s can be attributed to the formation of an excimer in the T1-state as a result of the T1-state selfquenching. |
| DOI: 10.12693/APhysPolA.89.527 PACS numbers: 33.50.Dq, 33.50.Hv, 35.80.Be |