Hydrogen-bond network in isomeric phenylenedipropynoic acids and their DABCO salts. Water mediated helical hydrogen bond motifs

The crystal structures of isomeric phenylenedipropynoic acids (PPA) are reported. 1,2-PPA shows an intra- and intermolecular hydrogen bonded 2D layered sheet structure. 1,4-PPA also has a 2D layered sheet structure. However the hydrogen bond is mediated by water molecules in the lattice. 1,3-PPA has an interpenetrating 3D structure without any void. The lattice of 1,3-PPA consists of two types of helical hydrogen bond network mediated by water molecules. The crystal structures of the DABCO salts of the 1,2-PPA and 1,4-PPA also show an interesting 3D and 2D hydrogen bond network, respectively. © 2009 The Royal Society of Chemistry.