MODIFICATION OF HOST PHOTOBEHAVIOR BY FORMATION OF CRYSTALLINE HOST-GUEST ASSEMBLIES

9,10-Dihydro-9,10-ethenoanthracene-11,12-bis(diphenylmethanol) (1) forms stable crystalline complexes with ethanol, acetone and toluene. In solution, diol 1 undergoes the di-pi-methane photorearrangement, but irradiation of the complexes in the crystalline state leads to a novel dehydration reaction. X-ray crystallography reveals the probable source of this difference in behavior: pre-organization of the hydroxyl groups in the solid state in a hydrogen-bonded arrangement that is particularly favorable for dehydration.