Crystal engineering involving C-H center dot center dot center dot N weak hydrogen bonds: A diquinoxaline lattice inclusion host with a preference for polychlorocarbon guests

dThe di(1,8-naphthryridine) 7 and diquinoxaline 12 derivatives were synthes ised as potential new lattice inclusion hosts where strong hydrogen bonding interactions would be absent. A number of potential supramolecular synthon s (such as aryl face-face, aryl edge-face, halogen-halogen C-H . . .N, nitr ogen-halogen) were expected to be accessible, with competing combinations o f these weak attractions providing the best (but probably different) type o f host-guest structure in each ease. While the former compound turned out t o be unstable, the latter proved to be a versatile host which preferred to trap small polychloroalkane guests. The X-ray structures of 12 . (chlorofor m)(2), (12)(2). (tetrahydrofuran), and (12)(2). (1,1,2,2-tetrachloroethane) are reported and shown to have different lattice packing where the guests occupy layers, parallel tubes, and molecular boxes, respectively. The detai led interplay of the above synthons in forming these structures is describe d in crystal engineering terms. Most significantly, the C-H . . .N weak hyd rogen bond plays a major role in all three inclusion structures. Both singl e linear and double cyclic interactions are involved in molecular edge-edge assembly of the host 12. Several new types of double cyclic interactions w ere discovered revealing that the C-H . . .N interaction is a key synthon f or crystal engineering involving nitrogen heteroaromatic compounds.