Photoinduced electron transfer chemistry of 9-methylanthracene. Substrate as both electron donor and acceptor in the presence of the 1-ethyl-3-methylimidazolium ion

Photolysis of 9-methylanthracene (2a; 9-CH(3)An) in a deoxygenated molten salt consisting of 1-ethyl-3-methylimidazolium chloride (1; EMIC) (55 mol %) and AlCl3 at room temperature yielded, in addition to the anti 4 + 4 dimer (3), six products, four of which are dimeric (two oxidized [8 and 9]; two neutral [4 and 5]) and two of which are monomeric (one reduced [7]; one neutral [6]). The same products were produced in CH3CN containing 1. These six products arose by initial electron transfer from 9-MeAn*(1) to EMI(+) to form the radical cation of 9-MeAn and EMI(.). The reduced product 7 arose by electron transfer from EMI(.) to 9-MeAn. This system thus contained both the radical cation and radical anion of 9-MeAn at different stages of the reaction. Experiments using 9-CD(3)An, 2-deuterioEMIC, and 2,4,5-trideuterioEMIC in the molten salt and 9-CH(3)An in the presence of N-1-butylpyridinium chloride (BPC) (BPC/CH3CN) and the molten salt BPC [55 mol %]/AlCl3 clarified mechanistic details.