Acta Crystallographica Section C

Crystal Structure Communications

Volume 65, Part 5 (May 2009)

organic compounds

Acta Cryst. (2009). C65, o217-o221 [ doi:10.1107/S0108270109012530 ]

A two-dimensional network in the molecular salt 2-methylimidazolium hydrogen glutarate, and three-dimensional networks in the salts 2-methylimidazolium hydrogen succinate and 2-methylimidazolium hydrogen adipate monohydrate

X.-G. Meng, C.-X. Cheng and G. Yan

Abstract: All three title compounds, C₄H₇N₂⁺·C₄H₅O₄^-, (I), C₄H₇N₂⁺·C₅H₇O₄^-, (II), and C₄H₇N₂⁺·C₆H₉O₄^-·H₂O, (III), can be regarded as 1:1 organic salts. The dicarboxylic acids join through short acid bridges into infinite chains. Compound (I) crystallizes in the noncentrosymmetric Cmc2₁ space group and the asymmetric unit consists of a hydrogen succinate anion located on a mirror plane and a 2-methylimidazolium cation disordered across the same mirror. The other two compounds crystallize in the triclinic P $\overline{1}$ space group. The carboxylic acid H atom in (II) is disordered over both ends of the anion and sits on inversion centres between adjacent anions, forming symmetric short OHO bridges. Two independent anions in (III) sit across inversion centres, again with the carboxylic acid H atom disordered in short OHO bridges. The molecules in all three compounds are linked into two-dimensional networks by combinations of imidazolium-carboxylate N⁺-HO and carboxylate-carboxylate O-HO hydrogen bonds. The two-dimensional networks are further linked into three-dimensional networks by C-HO hydrogen bonds in (I) and by O_water-HO hydrogen bonds in (III). According to the [Delta] pK_a rule, such 1:1 types of organic salts can be expected unambiguously. However, a 2:1 type of organic salt may be more easily obtained in (II) and (III) than in (I).

Formula: C₄H₇N₂⁺·C₄H₅O₄^-, C₄H₇N₂⁺·C₅H₇O₄^- and C₄H₇N₂⁺·C₆H₉O₄^-·H₂O


	Structure factor file (CIF format) (32.8 kbytes) [ doi:10.1107/S0108270109012530/sk3296Isup2.hkl ] Contains datablock I

	Structure factor file (CIF format) (105.8 kbytes) [ doi:10.1107/S0108270109012530/sk3296IIsup3.hkl ] Contains datablock II

	Structure factor file (CIF format) (118.9 kbytes) [ doi:10.1107/S0108270109012530/sk3296IIIsup4.hkl ] Contains datablock III

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