Photodimerization of anthracene derivatives in their neat solid state and in solid molecular compounds

The Cambridge Crystallographic Data Center provides valuable data for analysis and detection of compounds with potential to undergo photodimerization in the solid-state. Such analysis is presented for anthracene derivatives, and showed that there are many compounds that their packing in the crystal meets the requirement needed for [4 + 4] photodimerization in the solid-state. The crystal structures of various neat acyl anthracenes before and after exposure to UV light are described and the molecular structures of the dimers are compared with those obtained by exposing molecular compounds possessing a light-stable host (1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol) and light-sensitive acyl anthracenes. While exposing neat compounds to UV light causes disintegration of the single crystal, the reaction in the molecular compounds proceeds in a single-crystal to single-crystal mode until a certain rate of conversion, and then disintegrates.