Transient Photochemistry of Safranin-O.
Abstract
We have characterized the spectra, acidity constants and decay kinetics of the triplet and semireduced radical species of Safranin-O. Between pH 3.0 and pH 10.6 there are three triplet species denoted (3)DH2(+2), (3)DH(+) and (3)D, the pK(sub a)s being 7.5 and 9.2. All three triplet species exhibit first order decay, the rate constant for (3)DH2(+2) being circa 5-fold lower than the rate constants of (3)DH(+) and (3)D. Ascorbic acid and ethylenediaminetetraacetic acid quench the triplet state under appropriate pH conditions and the pH dependencies of the yield of semireduced dye indicate that (3)DH2(+2) is more reactive than (3)DH(+) or (3)D. With ethylenediaminetetraacetic acid as reducing agent, there is the additional requirement that at least one of the amino nitrogens be deprotonated to obtain a significant yield of semireduced dye. In these reactions, ascorbic acid is oxidized reversibly, but ethylenediaminetetraacetic acid is oxidized irreversibly, so that with the latter reducing agent photolysis causes buildup of the leucodye, which on subsequent photolysis can reduce triplet state dye. With ascorbic acid as reducing agent, the regeneration of the ground state dye is reversible, the decay of the semireduced radical being second order.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1980
- Accession Number
- ADA093354
Entities
People
- C. E. Baumgartner
- D. A. Aikens
- H. H. Richtol
Organizations
- Rensselaer Polytechnic Institute