Reduction of triphenyl methane dyes by the diphenyl ketyl radical and hydrated electrons: a time-resolved study
✍ Scribed by A.C. Bhasikuttan; L.V. Shastri; A.V. Sapre; K.V.S. Rama Rao; J.P. Mittal
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 742 KB
- Volume
- 84
- Category
- Article
- ISSN
- 1010-6030
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✦ Synopsis
The reduction of four triphenyl methane (TPM) dyes (brilliant green (BG+), malachite green (MG' ), crystal violet (CV+) and methyl green (MEG"))
by diphenyl ketyl radicals (BPH' ) and hydrated electrons (e,,-) was studied by pulse radiolytic kinetic spectrophotometry.
The rate constants for the reaction of BPH' with the cationic dyes are (S.O,t 1.0) X 108, (1.5 +0.2)X 109, (4.0+0.5)X 108 and (l.O+ 0.15) X 10" dm3 molt' s-' respectively and for the reaction with e,,-arc (9.5il.O) X 109, (9.3+1.0)X 109, (4.0+0.7)X 10" and (3.750.4)X 1O1" dm3 mol-' SK' respectively.
The transient spectra resulting from the reduction of the dyes were characterized. The time-resolved spectra and pH variation indicate that the dye radical generated from the e/ reaction is subsequently protonated.
The dye radicals decay by a second-order process without giving rise to bleach recovery.