On the photoreduction of crystal violet, phenosafranine and methylene blue by benzophenone

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Chemistry., 1992-02, Vol.63 (2), p.217-226
• Main Authors: Jockusch, S., Timpe, H.J., Fischer, Ch.-H., Schnabel, W.
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics)
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/1010-6030(92)85139-L

Benzophenone triplets ( 3BP*) react very effectively with the cations of crystal violet (CV +, methylene blue (MB +) and phenosafranine (PS +) in argon-saturated acetonitrile solution at 23 °C: k q values (in M −1 s −1) are (3 ± 1) × 10 10 (CV +), (7 ± 1) × 10 9 (MB +) and (5 ± 1) × 10 9 (PS +). The results suggest that electron transfer occurs in the system 3BP*—CV +, whereas triplet energy transfer is the dominant reaction route in the other two cases. Substituted methyl radicals generated by the reaction of 3BP* with several amines (triethanol amine, triethyl amine, dimethyl and diethyl aniline) are effectively oxidized by the three dye cations. Electron transfer rate constants k e ranging from 0.6 × 10 10 to 3 × 10 10 M −1 s −1 were determined. The dye cations are less reactive towards ketyl radicals, e.g. k e[(Ph) 2C(OH) + CV +] ≈ 2 × 10 8 M −1 s −1 and k e[(CH 3) 2COH + CV +] ≈ 1.3 × 10 9 M −1 s −1.