Acta Crystallographica Section C

Structural Chemistry

Volume 70, Part 2 (February 2014)

organic compounds

bg3168 scheme

Acta Cryst. (2014). C70, 225-229    [ doi:10.1107/S2053229614001090 ]

Supra­molecular association in proton-transfer adducts containing benz­amidinium cations. III. Three mole­cular salts of 3-meth­oxy-, 4-meth­oxy- and 3,4,5-tri­meth­oxy­benzoates with benzamidine

G. Portalone

Abstract: Three mol­ecular salts, benzamidinium 3-meth­oxy­benzoate, C7H9N2+·C8H7O3-, (I), benzamidinium 4-meth­oxy­benzoate, C7H9N2+·C8H7O3-, (II), and benzamidinium 3,4,5-tri­meth­oxy­benzoate monohydrate, C7H9N2+·C10H11O5-·H2O, (III), were formed from the proton-transfer reactions of 3-meth­oxy, 4-meth­oxy- and 3,4,5-tri­meth­oxy­benzoic acids with benzami­d­ine (benzene­carboximidamide, benzam). Monoclinic salts (I) and (II) have a 1:1 ratio of cation to anion. In monoclinic salt (III), two cation-anion pairs and two water mol­ecules constitute the asymmetric unit. In all three mol­ecular salts, the amidinium fragments and the carboxyl­ate groups are completely delocalized, and the delocalization favours the aggregation of the mol­ecular components into nonplanar dimers with an R22(8) graph-set motif by N+-H...O- (±) charge-assisted hydrogen bonding (CAHB). Of the three mol­ecular salts, (I) and (II) show similar conformations of the anionic components and exhibit bidimensional isostructurality, which consists of alternating R22(8) and R46(16) rings resulting in a corrugated sheet propagated parallel to the crystallographic ab plane. In mol­ecular salt (III), the R22(8) synthon is retained but the supra­molecular structure is different, due to the presence of three bulky meth­oxy substituents and a water mol­ecule. The structures reported here further demonstrate the robustness of R22(8) hydrogen-bonded synthons having the benzamidinium cation as a building block, whereas N+-H...O- hydrogen bonds external to the salt bridge contribute to the overall structure organization.

CCDC references: 981710, 981711 and 981712

Formula: C7H9N2+·C8H7O3-, C7H9N2+·C8H7O3- and C7H9N2+·C10H11O5-·H2O

Keywords: crystal structure; benzamidinium salts; proton-transfer adducts; charge-assisted hydrogen bonds.

hkldisplay filedownload file

Structure factor file (CIF format) (125.0 kbytes)
[ doi:10.1107/S2053229614001090/bg3168Isup2.hkl ]
Contains datablock I

hkldisplay filedownload file

Structure factor file (CIF format) (213.7 kbytes)
[ doi:10.1107/S2053229614001090/bg3168IIsup3.hkl ]
Contains datablock II

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Structure factor file (CIF format) (382.4 kbytes)
[ doi:10.1107/S2053229614001090/bg3168IIIsup4.hkl ]
Contains datablock III


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