Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
26874 | Journal of Photochemistry and Photobiology A: Chemistry | 2012 | 7 Pages |
The splitting quantum yields of the dimer by tethered chromophores exhibited different solvent effects. To further explore mechanism of the solvent effects, three covalently linked phenothiazine–dimer model compounds with a short linker, 1a–1c, were prepared. It was observed that solvent effect on dimer-splitting efficiency for phenothiazine–dimer systems is contrary to that of the other chromophore–dimer systems. Calculated results based on the Marcus theory showed that phenothiazine systems with a lower driving force induced by a lower value of Eox have a longer donor–acceptor distance between phenothiazine moiety and dimer unit, then gives a higher λs. Thus, back electron transfer would lie in the Marcus normal region for phenothiazine–dimer models, in which dimer-splitting is more efficient in higher polarity solvents. The value of redox potential between a donor and an acceptor should be a key leading to back electron transfer lying in the different Marcus regions and following two reverse solvent effects. Moreover, fluorescence spectra showed that the dual fluorescence gives a hint of charge-transfer complexes, and partial charge transfer would lead to lower splitting efficiency. However, some new insights into mechanisms of DNA photoreactivation mediated by photolyases were gained.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The dimer-splitting for phenothiazine–dimer models with a short linker is faster in higher polarity solvents. ► This solvent effect is contrary to that of the other chromophore–dimer systems. ► The value of redox potential should be a key leading to two reverse solvent effects according to Marcus theory. ► Charge-transfer complexes would lead to lower splitting efficiency.