Identification of a new supramolecular synthon in o-anisaldehydes: molecular self-assembly into tapes and staircases

We have shown through a rational design, synthesis and X-ray structural analyses of a set of aldehydes that omethoxybenzaldehydes tend to associate in a centrosymmetric fashion, akin to the carboxylic acids, to give rise to a dimer motif II, which derives stabilization from four C–H/O hydrogen bonds in addition to a dipole–dipole interaction. That the synthon II is credible to be structure determining is revealed from the crystal structures of aldehydes 1–4 that are devoid of any other competing weak interactions. The aldehydes 1–4 are found to undergo self-assembly into 1-dimensional molecular tapes and staircases. We have shown that the steric factors as in aldehyde 5 and the presence of a functional group such as Br in 6 perturb the expected crystal packing based on synthon II. q 2005 Elsevier B.V. All rights reserved