Crystal structures of 1,4-di-aza-bicyclo-[2.2.2]octan-1-ium 4-nitro-benzoate dihydrate and 1,4-di-aza-bicyclo-[2.2.2]octane-1,4-diium bis-(4-nitro-benzoate): the influence of solvent upon the stoichiometry of the formed salt.

ABSTRACT: The 1:1 co-crystallization of 1,4-di-aza-bicyclo-[2.2.2]octane (DABCO) with 4-nitro-benzoic acid in ethanol-water (3/1) gave the salt dihydrate C6H13N2 (+)·C7H4NO4 (-)·2H2O, (1), whereas from methanol, the salt C6H14N2 (2+)·2C7H4NO4 (-), (2), was isolated. In (1), the cation and anion are linked by a strong N-H?O hydrogen bond, and the carboxyl-ate anion is close to planar [dihedral angle between terminal residues = 6.83?(9)°]. In (2), a three-ion aggregate is assembled by two N-H?O hydrogen bonds, and the carboxyl-ate anions are again close to planar [dihedral angles between terminal residues = 1.7?(3) and 5.9?(3)°]. Through the inter-vention of solvent water mol-ecules, which self-assemble into helical supra-molecular chains along the b axis, the three-dimensional architecture in (1) is stabilized by water-DABCO O-H?N and water-carboxyl-ate O-H?O hydrogen bonds, with additional stability afforded by C-H?O inter-actions. The global crystal structure comprises alternating layers of water mol-ecules and ion pairs stacked along the c axis. In the crystal of (2), the three-ion aggregates are assembled into a three-dimensional architecture by a large number of methyl-ene-carboxyl-ate/nitro C-H?O inter-actions as well as ?-? contacts between inversion-related benzene rings [inter-centroid distances = 3.5644?(16) and 3.6527?(16)?Å]. The cations and anions assemble into alternating layers along the c axis.

SUBMITTER: Akhmad Aznan AM 

PROVIDER: S-EPMC4120614 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature