Res. Chem. Intermed.
, Vol. 30, No. 6, pp. 637–646 (2004)
Also available online - www.vsppub.com
Redox reactions of basic fuchsin in homogeneous aqueous
S. N. GUHA and HARI MOHAN
Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre,
Mumbai 400 085, India
Received 22 December 2003; accepted 15 April 2004
Abstract—The pulse-radiolysis technique has been employed to understand the reaction mechanism
and to characterize the transient species involved in the redox processes taking place in the radiation
chemistry of basic fuchsin (BF
). One-electron reduction and oxidation reactions of BF
carried out in homogeneous aqueous solutions employing various reducing (e
and oxidizing (N
) radicals. The absorption spectra of the transients formed in the
above reactions have been attributed to semi-reduced and semi-oxidized species of BF
The kinetic and spectroscopic properties of these transients have been evaluated. The reaction with
OH radicals have also been performed and compared with those of speciﬁc one-electron
reducing and oxidizing radicals. These reactions have been inferred predominantly by addition to
. Protolytic equilibria involving semi-reduced species of basic fuchsin have been studied over the
pH range from 2 to 10 and the pK
has been determined to be 3.9.
Keywords: Fuchsin; redox reaction; pulse radiolysis; protolytic equilibrium.
Organic dyes have been used in photo-electrochemical energy conversion devices,
where their redox chemistry plays an important role [1, 2]. There have been
reports in the past that use of these dyes as sensitizers in photo-electrochemical
devices for solar energy conversion suffer from poor power conversion efﬁciency
[3, 4]. This drawback has been mainly attributed to slow discharge of photo-
produced intermediate dye radical at the cell electrode as compared to radical–
radical recombination reactions in the bulk of the solution. To make the discharge
process favourable, it is necessary to arrest the recombination reaction in the bulk
homogeneous phase. Attempts have been made in the past to slow down the bulk
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