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The Effect of Environment and Substituents on the Photochemical Activity of Anthraquinonoid Vat Dyes and the Rôle of n‐π* Transitions
Author(s) -
Bridge N. K.
Publication year - 1960
Publication title -
journal of the society of dyers and colourists
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.297
H-Index - 49
eISSN - 1478-4408
pISSN - 0037-9859
DOI - 10.1111/j.1478-4408.1960.tb02391.x
Subject(s) - flash photolysis , photochemistry , singlet state , chemistry , spectroscopy , triplet state , absorption (acoustics) , fluorescence , absorption spectroscopy , computational chemistry , molecule , excited state , organic chemistry , materials science , kinetics , atomic physics , physics , reaction rate constant , quantum mechanics , composite material
The well‐established correlations between dye fading and the phototendering caused by vat dyes on the one hand and dye affinity, aggregation, radical stability, electromeric effects, etc., on the other, are reviewed. Recent work, including flash spectroscopy, photolysis of model systems, studies of fluorescence and absorption spectroscopy, and studies indicating the existence of both singlet and triplet n–* transitions, is discussed, and this leads to the suggestion that n–* transitions are of fundamental importance. Evidence is collected to substantiate this. Factors which may affect the transition, especially hydrogen bonds involving the n ‐electrons and electromeric effects, are considered, as well as processes influencing the singlet‐triplet ratio. It is shown, in terms of the relative amounts of singlet and triplet formed, how the observed difference between the efficient cyclic process of photosensitisers can be explained. Finally, these arguments are applied to a few well‐known regularities of commercial dyes.