Attack of H-atoms on aqueous thionine studied by pulse radiolysis

Abstract

SONIA SOLAR, NIKOLA GETOFF, WOLFGANG SOLAR, and FRANZ MARK. Can. J. Chem. 59,2719Chem. 59, (1981.The reaction mechanism of the H-attack on thionine (TH+) in aqueous solutions (5 X to 2 X mol dm+ TH+; 2 x mol dm-3 r-butanol, pH I and 4) was investigated by pulse radiolysis in combination with simulation by computation. Applying a least-squares fitting procedure it was possible to state that at pH 1,89.5% of the H-atoms react with TH+, k = (8.5 f 0.3) x lo9 dm3 mol-I s-I, to form semiquinone ('TH3Z+, Amax = 390nm, E,,, = 685 f 20 m2 mol-I; &770 = 720 mZ mol-' and Amax = 790nm, E, , , = 775 f 20mZ mol-I), which dismutates to TH+ and leucodye with 2k = (2.4 f 0.1) X lo9 dm3 mol-I s-I. In addition to this a second H-attack (10.5% H) occurs on the ring carbon of the dye with k = (1.0 f 0.1) x lo9 dm3 mol-' s-l, resulting in the production of H-adducts. These results are of interest for photogalvanic cells using thionine as a sensitizer., SONIA SOLAR, NIKOLA GETOFF, WOLFGANG SOLAR et FRANZ MARK. Can. J. Chem. 59,2719Chem. 59, (1981.Utilisant la radiolyse par pulsation combinee avec une simulation obtenue par le calcul, on a ttudie le mecanisme de la reaction 1 d'attaque du H sur la thionine (TH+) dans des solutions aqueuses (5 x a 2 x mol dm-' TH+; 2 x mol d m 3 rerr-butanol,

Thionine Fluorescence Quenching by Metal Cations

“…*) Note added in proof: This value is in very good agreement with k$ = 2.8 X 10 9 dm 3 mol -1 s -1 determined by pulse radiolysis very recently [34]. where kF = 1.3 X 10 8 s -i [5]; Q¥ = 0.047 [12].…”

Kinetics of Photochemical Reactions of Thionine with Thiourea

“…Th · H ϩ ϩ AH 2 (12) The triplet state is supposed to react with reductant forming semithionine: Th · H ϩ 2 ϩ AH (13) In the triplet state the excited thionine may from cation Th · H ϩ by intersystem crossing:…”