Solid-State Photolysis of Anthracene-Linked Ammonium Salts: The Search for Topochemical Anthracene Photodimerizations

The reaction of 9-N,N-dimethylaminomethylanthracene 1 with aromatic carboxylic acids gave crystalline salts (2a, 2b, 3a and 3b), which were irradiated in the solid state. Whereas salt 3a was selectively transformed to the dimer 4a, the other salts were photoinert. The results were rationalized on the basis of X-ray structure analysis. In the presence of oxygen, solid-state irrradiation of anthracene salt 3b leads to selective photooxygenation. The selectivity of both solid-state photoreactions was not observed in solution.