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A STUDY OF THE SAFRANINE‐ASCORBIC ACID PHOTOCHEMICAL REDOX REACTION
Author(s) -
WONG H. K.
Publication year - 1968
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.1751-1097.1968.tb08026.x
Subject(s) - chemistry , photochemistry , radical , ascorbic acid , flash photolysis , redox , aqueous solution , triplet state , yield (engineering) , kinetics , reaction rate constant , inorganic chemistry , organic chemistry , molecule , physics , food science , quantum mechanics , materials science , metallurgy
— Flash‐photolysis of safranine in deoxygenated 5 per cent aqueous pyridine produces a transient bleaching, which disappears by a second order process. Very probably this transient species consists of a pair of radicals or radical ions and not of the safranine in the triplet state. These radicals are also produced in chlorophyll sensitized reactions. Present results combined with previous work by us[I] indicate that the chlorophyll sensitization of safranine bleaching involves the formation of these radicals. The direct photochemical reduction of safranine to its leuco form occurs through the intermediate formation of the radicals. The appearance and disappearance of these radicals is fast compared to the role of photochemical formation and thermal disappearance of leuco safranine. Ascorbic acid influences but is not essential to the photo‐bleaching of safranine in 5 per cent aqueous pyridine. An increase in ascorbic acid concentration increases the steady‐state yield of the radicals but decreases the steady‐state yield of the leuco safranine. In the absence of ascorbic acid or other added substance, safranine photobleaches irreversibly in deoxygenated 5 per cent aqueous pyridine. A plausible mechanism is proposed in explanation of the direct photochemical reduction of safranine.