title: Helical self-assembly of substituted benzoic acids: influence of weaker X...X and C-H...X interactions.
abstract: The X-ray crystal packing analyses of the sterically encumbered halogen-substituted benzene carboxylic acids 1-4 reveal a novel and unprecedented crystal packing in that the association of the carboxyl groups through O-H...O bonds results in the generation of a helix along the 41-screw axis. Such an organization of the acids is shown convincingly to be a result of the close packing, which exploits the weaker X...X and C-H...X interactions in conjunction with the stronger O-H...O hydrogen bonds. In contrast, the chloro- and bromo-substituted durene carboxylic acids 6 and 7 exhibit a pattern that is akin to tape/ribbon involving the centrosymmetric-dimer motif and X...X short intermolecular interactions. The structural investigations demonstrate the ability of the weaker interactions in modifying the supposedly "robust" centrosymmetric-dimer motif of the carboxyl groups in a decisive manner.
authors.affiliation: Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India.
authors.forename: J Narasimha
authors.initials: JN
authors.lastname: Moorthy
authors.forename: R
authors.initials: R
authors.lastname: Natarajan
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Mal
authors.forename: P
authors.initials: P
authors.lastname: Venugopalan