MOLECULAR SYMMETRY AND THE DESIGN OF MOLECULAR-SOLIDS - THE OXALAMIDEFUNCTIONALITY AS A PERSISTENT HYDROGEN-BONDING UNIT

A symmetry analysis based upon the structure of simple molecules and t heir anticipated intermolecular interactions can lead to successful pr edictions of molecular packing and crystal symmetry, As a demonstratio n of these ideas an in-depth study of the oxalamide functionality as a persistent hydrogen bonding unit is presented. The synthesis and stru ctural characterization of a series oxalamide dicarboxylic acids is pr esented and the structures compared with the analogous urea compounds. Both the urea and oxalamide dicarboxylic acids form designed two-dime nsional hydrogen-bonded beta-networks with a significant degree of rel iability, The urea designs are quite reliable when there is a molecula r 2-fold axis, but competing hydrogen bond patterns are found when les s symmetrical molecules are studied. The oxalamide design based on inv ersion centers is also quite reliable, with the designed layer structu re found in most cases.