Synthesis and structure of tris(2-methyl-1<i>H</i>-imidazol-3-ium) 5-carboxybenzene-1,3-dicarboxylate 3,5-dicarboxybenzoate

The structure of the title salt, 3C₄H₇N₂ ⁺·C₉H₅O₆ ^-·C₉H₄O₆ ^2-, <b>1</b>, consists of three 2-methyl-imidazolium cations and both a single and a doubly deprotonated form of trimesic acid as anions. A detailed analysis of the bond lengths and angles reveals both differences and similarities between compound <b>1</b> and the previously reported 2-methyl-1<i>H</i>-imidazol-3-ium 3,5-di-carb-oxy-benzoate structure [Baletska <i>et a</i>l. (2023). <i>Acta Cryst.</i> E<b>79</b>, 1088-109], as well as the neutral counterpart of the ions. Examination of the crystal packing shows the formation of infinite chains by the anions, which, along with the cations, form zigzag planes parallel to the <i>ab</i> plane. The packing inter-actions are primarily driven by π-π inter-actions and hydrogen bonding between anions.