Dimeric C-H•••N interactions and the crystal engineering of new inclusion host molecules

Single crystal X-ray studies of (6). (tetrahydrofuran)(2) and (6). (benzene)(1.5) reveal the presence of two distinct types of dimeric edge-edge C-H . . .N packing motifs. All of the racemic dibromides 2-4 and 6 form clathrate compounds where their opposite enantiomers are joined edge-edge by means of C-H . . .N dimers. Hence this interaction is robust and of considerable value in crystal engineering. Modification of the benchmark centrosymmetric aryl-H . . .N dimer can result, however, in more complex modifications which better suit a given host-guest combination. Therefore a range of different C-H . . .N dimers is observed, with the new motif present in (6). (benzene)(1.5) completing a sub-set of these variants. This structural adaptability increases the likelihood of inclusion because competition between many weak intermolecular contacts is a central part of the host design philosophy.