Water-Soluble Phosphaviologens for Effective Photoinduced Charge Separation

Two highly water-soluble phosphaviologens were synthesized via effective protocols requiring as little as two steps and only minimal purification. The new species were purposefully designed for potential application in photocatalysis as a binary system in conjunction with titanium dioxide (anatase). To this end, the efficacy of the new materials for effective charge separation was investigated via photodegradation of methylene blue. In addition to improved aqueous solubility of the phosphaviologens, we successfully inhibited the photodegradation of methylene blue in comparison to pristine TiO₂ due to the highly electron accepting properties of phosphaviologens, which can effectively accept a photoexcited electron from TiO₂. We also went on to compare our phosphaviologens to traditional viologens, revealing that they are equally as effective in creating a charge-separated state for TiO₂.