Supramolecular association in proton-transfer adducts containing benzamidinium cations. I. Four molecular salts with uracil derivatives
作者:Gustavo Portalone
DOI:10.1107/s0108270110016252
日期:2010.6.15
Four organic salts, namely benzamidinidium orotate (2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylate) hemihydrate, C7H9N2+center dot C5H3N2O4-center dot 0.5H(2)O (BenzamH(+)center dot Or(-)), (I), benzamidinium isoorotate (2,4-dioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylate) trihydrate, C7H9N2+center dot C5H3N2O4-center dot 3H(2)O (BenzamH(+)center dot Isor(-)), (II), benzamidinium diliturate (5-nitro-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate) dihydrate, C7H9N2+center dot C4H2N3O5-center dot 2H(2)O (BenzamH(+)center dot Dil(-)), (III), and benzamidinium 5-nitrouracilate (5-nitro-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-ide), C7H9N2+center dot C4H2N3O4- (BenzamH(+)center dot Nit(-)), (IV), have been synthesized by a reaction between benzamidine (benzenecarboximidamide or Benzam) and the appropriate carboxylic acid. Proton transfer occurs to the benzamidine imino N atom. In all four acid-base adducts, the asymmetric unit consists of one tautomeric aminooxo anion (Or(-), Isor(-), Dil(-) and Nit(-)) and one monoprotonated benzamidinium cation (BenzamH(+)), plus one-half (which lies across a twofold axis), three and two solvent water molecules in (I), (II) and (III), respectively. Due to the presence of protonated benzamidine, these acid-base complexes form supramolecular synthons characterized by N+-H center dot center dot center dot O- and N+-H center dot center dot center dot N- (+/-)-charge-assisted hydrogen bonds (CAHB).