Dimeric C–H⋯N interactions and the crystal engineering of new inclusion host molecules

Abstract

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.