Edge-to-edge aryl C–H · · · N dimer: a new supramolecular synthon

Abstract

Study of the lattice packing in the crystal structures of the diquinoline compounds 1 [C₂₃H₁₈N₂, P, a = 6.1953(8), b = 11.427(2), c = 12.686(2) Å, α = 108.428(7), β = 92.189(8), γ = 103.437(7)°, Z = 2, R = 0.038] and 2·CHCl₃ [C₂₃H₁₆Br₂N₂·CHCl₃, P2₁/c, a = 9.865(3), b = 15.307(3), c = 17.946(5) Å, β = 122.12(1)°, Z = 4, R = 0.031] reveals a previously unrecognised mode of intermolecular attraction which we term the edge-to-edge aryl C–H · · · N dimer. Examination of the Cambridge Structural Database shows that this type of contact is present in a wide range of nitrogen-containing aromatic solids. In all 54 identified cases the two weak intermolecular hydrogen bonds are identical producing a symmetrical dimer and, in all cases but one, the arrangement created is centrosymmetric. Hence this new packing mode represents a predictable new synthon for supramolecular assembly.