Pi-halogen dimer interactions and the inclusion chemistry of a new tetrahalo aryl host.

The preparation of 1,4,8,11-tetrabromo-5b[small alpha],6,12b[small alpha],13-tetrahydropentaleno[1,2-b:4,5-b[prime or minute]]diquinoline is described. This is a further member of the tetrahalo aryl host family, and forms crystalline lattice inclusion compounds with many guests. The X-ray structures of the allyl cyanide, 1,2,3-trichloropropane, chlorobenzene, toluene, benzene-water, methyl chloroform and carbon tetrachloride inclusion compounds are described, and compared with that of the solvent-free apohost. Although several different structural types are produced, the recently reported pi-halogen dimer (PHD) interaction plays an important role in all of these, except for that of pure (where the packing energy is the least favourable of the series).