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INCREASED QUANTUM YIELD OF PHOTOREDUCTION OF DYES (A CATALYTIC EFFECT)
Author(s) -
Steiner U.,
Hafner M.,
Schreiner S.,
Kramer H. E. A.
Publication year - 1974
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1974.tb06487.x
Subject(s) - thionine , photochemistry , quantum yield , flash photolysis , chemistry , radical , azulene , yield (engineering) , kinetics , materials science , organic chemistry , reaction rate constant , optics , electrochemistry , physics , electrode , quantum mechanics , metallurgy , fluorescence
— While studying the photoreduction of some dyes (D) by reducing agents (R), it was observed that the quantum yield of the photoreduction increases considerably upon addition of a third substance (C), whereas it is very small when the dye is photoreduced by C alone (catalytic effect), (see Table 1). The system thionine (D), allylthiourea (R), and azulene (C) was investigated in detail using both flash photolysis and continuous illumination. On photolysis, thionine is converted into its photo‐reduced form, leucothionine. Azulene reacts with the basic form of the thionine triplet 3 TH + to produce the semithionine radical. In the system thionine and azulene, most of these radicals revert back to thionine. When ATU (˜ 10 2‐ M ) is added to thionine and azulene (3 × 10 ‐4 M ), the semithionine radicals are reduced to leucothionine; the quantum yield of this reduction is considerably higher than in the system thionine and allylthiourea. Flash experiments demonstrate that allylthiourea does not react with the semithionine radicals. At very high ATU concentrations (≥ 10 ‐1 M ), however, the primary reaction is between thionine triplet and allylthiourea; under these conditions the quantum yield is not influenced by azulene (3 × 10 ‐4 M ).