Synthesis of methylviologen-HTiNbO₅ intercalation compound and its photochemical behavior

A novel intercalation compound composed of layered titanoniobic acid (HTiNbO₅) and methylviologen was synthesized and its photochemical behavior was investigated. Although methylviologen could not be intercalated into the interlayer region of titanoniobic acid directly, the intercalation compound was obtained by guest exchange with the propylammonium-HTiNbO₅ intercalation compound. When the viologen intercalated compound was irradiated by UV light under an N₂ atmosphere or under a vacuum, the compound turned blue. Visible spectroscopy and ESR indicated the formation of viologen radical cations. The phenomenon was thought to be due to the electron transfer from the oxygen-deficient layered oxide to the viologen. The oxidation of the viologen radical cations did not occur under O₂-free conditions; therefore the oxygen was responsible for the bleaching.