Photoinduced Redox Reactions Catalyzed by 9-Substituted Acridinium Ions

Abstract

Endergonic photoinduced redox reactions in deaerated acetonitrile (MeCN) between 1-benzylnicotinamide (BNAH) and hexylviologen occur efficiently in the presence of 9-mesitylacridinium ion acting as a photocatalyst with 360 nm photoirradiation. The quantum yield of the caralytic reaction is determined as 30%. The oxidation of anthracene also occurs with 9-mesityl acridinium ion in deaerated acetonitrile with 430 nm photoirradiation. The decay of absorbance at 480 nm due to mesitylene radical cation coincides with the appearance of absorbance at 720 nm due to anthracene radical cation. Both the decay and formation rates obey first-order kinetics. The electron transfer rate constant from anthracene to mesitylene radical cation is determined as 6.8 x 10⁹ M^-1 s^-1. In the presence of oxygen, anthracene is photooxydized in the presence of 9-mesityl acridinium ion with 430 nm photoirradiation to yield anthraquinone and hydrogen peroxide in acetonitrile.