A Tetrachloro Guest in a Molecular Box

Abstract

The new lattice inclusion host exo-7,exo-15-dibromo-6,7,14,15-tetrahydro-6,14-methanocycloocta[1,2-b:5,6-b'] diquinoxaline (6) has been synthesized in three steps from bicyclo [3.3.1]nonane-2,6-dione and benzofurazan oxide. It preferentially forms crystalline inclusion compounds with small polyhaloalkane guest molecules, and the crystal structure of the 1,1,2,2-tetrachloroethane compound [(C₂₁H₁₄N₄Br₂)₂.C₂H₂Cl₄, Pbcn , a 11.663(2), b 13.195(3), c 27.444(5) Ǻ, Z 4, R 0.041] is described. The key characteristic of this compound is a series of molecular boxes in which the guest molecules reside. Construction of the six surrounding walls is achieved with the aromatic rings of just four host molecules, and the guest molecule occupies a fixed position within the box. The intermolecular forces resulting in formation of this novel inclusion structure are analysed in detail.