Role of double C-H•••N weak hydrogen bonding motifs in N-heteroaromatic inclusion chemistry

Dibromodiquinoline 8 forms lattice inclusion compounds when crystallized from solvents such as dichloromethane, tetrahydrofuran, chloroform, and benzene. The crystal structures of these compounds are described in crystal engineering terms, and are also compared with the solvent-free crystal structures of 8 and its nonbrominated precursor 6. Aromatic edge-edge double C-H...N interactions play a crucial role in all six solids. These comprise both cyclic hydrogen-bonded dimer and bifurcated C-H...N...H-C types. A diverse range of structurally different double C-H...N motifs is encountered in these, and closely related, compounds.