PULSE-RADIOLYSIS STUDY OF ONE-ELECTRON REDUCTION OF SAFRANINE-T

The one-electron reduction of safranine T by hydrated electrons and va rious reducing organic radicals in aqueous solution has been studied b y the technique of nanosecond pulse radiolysis. The absorption spectru m of the transient semireduced safranine formed in these reactions exh ibited lambda(max) at 400 and 650 nm with molar absorption coefficient values of 6.88 x 10(3) and 9.9 x 10(3) dm(3) mol(-1) cm(-1) respectiv ely and decayed obeying a second-order rate law with a bimolecular rat e constant of 0.97 x 10(9) dm(3) mol(-1) s(-1) at neutral pH. It has t wo pK(a) values of 3.0 and 8.5. The rate constants for the formation o f semireduced safranine species by the reactions of most of the reduci ng radicals with the dye were very high and nearly diffusion controlle d. The one-electron reduction potential of safranine T was estimated t o be -0.35 +/- 0.02 V as. NHE at pH 5. Reaction of H atoms with SF+ at acidic pH was also studied. The results obtained have been discussed with respect to the possibilities of different modes of H-atom reactio ns with safranine T.