EDGE-TO-EDGE ARYL C-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-N DIMER - A NEW SUPRAMOLECULAR SYNTHON

Study of the lattice packing in the crystal structures of the diquinol ine compounds 1 [C23H18N2, P (1) over bar, a = 6.1953(8), b = 11.427(2 ), c = 12.686(2) Angstrom, a = 108.428(7), beta = 92.189(8), gamma = 1 03.437(7)degrees, Z = 2, R = 0.038] and 2 . CHCl3 [C23H16Br2N2 . CHCl3 , P2(1)/c, a = 9.865(3), b = 15.307(3), c = 17.946(5) Angstrom, beta = 122.12(1)degrees, 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 sho ws that this type of contact is present in a wide range of nitrogen-co ntaining aromatic solids. In all 54 identified cases the two weak inte rmolecular hydrogen bonds are identical producing asymmetrical dimer a nd, in all cases but one, the arrangement created is centrosymmetric. Hence this new packing mode represents a predictable new synthon for s upramolecular assembly.