Solid‐State Photodimerization of Guest Molecules in Inclusion Compounds

Photochemical dimerization reactions of 1,3‐diphenyl‐1‐propen‐3‐one (chalcone), 9‐acetylanthracene, and 9‐(methoxycarbonyl)anthracene as guest molecules in inclusion compounds with 1,1,6,6‐tetraphenyl‐2,4‐hexadiyne‐1,6‐diol were studied. The irradiation of a single crystal containing chalcone was carried out in a single step and resulted in a single crystal containing the photodimer in full occupancy. In the case of the crystal containing 9‐acetylanthracene, X‐ray diffraction data were collected after irradiation for different periods of time. Only one of the two crystallographically independent pairs of 9‐acetylanthracene underwent solid‐state photodimerization at ca. 11 % conversion to the head‐to‐tail dimer. Photodimerization of the 9‐(methoxycarbonyl)anthracene inclusion compound led, after irradiation for 2.5 h, to ca. 37 % conversion. It was found that the molecules that were arranged in stacks had undergone photodimerization in two different ways, so that on the average it looked as if all the guest molecules had polymerized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)