Spectroelectrochemical analysis of the thionine transfer coupled to a photoinduced chemical reaction across the water|1,2-dichloroethane interface

Thionine (Thio+) is a dye used in photogalvanic and dye-sensitized solar cells to convert light into chemical energy. The photophysical properties of this cell are strongly affected by aggregate formation and polymerization of thionine because the monomer is the photoactive species. In this paper, we report the electrochemical interfacial transfer of thionine from water to 1,2 DCE and the further photochemical reaction upon illumination of this organic phase. Cyclic voltammetry coupled to interfacial absorbance measurements allowed us to perform a kinetic analysis. Values of εThio = (2.5 ± 0.1)104 M−1 cm−1, εproduct = (1.4 ± 0.1)10 4 M−1 cm−1 and a kinetic constant k = 0.28 ± 0.05 s−1 for the chemical reaction, were calculated by simulation of the interfacial absorbance profiles. NMR and UV-vis spectra of the phases at different pH values contributed to identify the nature of the reacting species of the chemical reaction and showed the important influence of pH on the kinetic of the process. The effect of the organic supporting electrolyte on the kinetics of the reaction was also analyzed.