Photochemical Electron Transport from Water Layer to Organic Layer via Sodium Anthraquinone-2-sulfonate by Stepwise Two Photon Excitation

Photochemical electron transport from hydroxide ion to organic acceptor molecule via an anthraquinone derivative as an electron carrier was investigated in homogeneous, cationic micellar, and cationic reversed micellar systems. In homogeneous alkaline aqueous ethanol, the photochemically generated radical anion of sodium anthraquinone-2-sulfonate (1) was stable against further irradiation with visible light (λ>450 nm), while the dianion of 1 was reversibly converted to the radical anion by visible light irradiation. The reversible conversion was accelerated by the addition of an organic acceptor molecule such as 1,4-dicyanobenzene. In a cationic hexa-decyltrimethylammonium micellar system, an effective photoreduction of 1 by an electron transfer from hydroxide ion concentrated on the micellar surface to the excited 1 located in the surface area of the micelle was observed. In a reversed micellar system an electron was effectively transported from the water layer to the organic layer; an electron was transfered from hydroxide ion in the water layer incorporated in a benzylhexadecyldimethylammonium reversed micelle to 1 at the micellar surface by irradiation with light of λ=365 nm. Successive visible light irradiation (λ>450 nm) caused an electron ejection from the radical anion of 1 to benzonitrile as a bulk phase solvent. The possibility of the incorporation of carbon dioxide into the acceptor cycle of the electron transport system was also examined. In pyridine solution, carbon dioxide caused the disappearance of the reduced species of 1 on visible light irradiation (λ>450 nm). Trace amounts of dihydropyridinedicarboxylic acid derivatives were obtained.