Structural characterization of two tetra-chlorido-zincate salts of 4-carb-oxy-1 H-imidazol-3-ium: a salt hydrate and a co-crystal salt hydrate

Abstract

Imidazole-containing compounds exhibit a myriad of pharmacological activities. Two tetra-chlorido-zincate salts of 4-carb-oxy-1H-imidazol-3-ium, ImHCO₂H⁺, are reported. Bis(4-carb-oxy-1H-imidazol-3-ium) tetra-chlorido-zincate monohydrate, (C₄H₅N₂O₂)₂[ZnCl₄]·H₂O, (I), crystallizes as a monohydrate salt, while bis-(4-carb-oxy-1H-imidazol-3-ium) tetra-chlorido-zincate bis-(1H-imidazol-3-ium-4-carboxyl-ato) monohydrate, (C₄H₅N₂O₂)₂[ZnCl₄]·2C₄H₄N₂O₂·H₂O, (II), is a co-crystal salt with six residues: two ImHCO₂H⁺ cations, two formula units of the zwitterionic 1H-imidazol-3-ium-4-carboxyl-ate, ImHCO₂, one tetra-chlorido-zincate anion and one water mol-ecule disordered over two sites in a 0.60 (4):0.40 (4) ratio. The geometric parameters of the ImHCO₂H⁺ and the ImHCO₂ moieties are the same within the standard uncertainties of the measurements. Both compounds exhibit extensive hydrogen bonding, including involvement of the tetra-chlorido-zincate anion, resulting in inter-connected chains of anions joined by water mol-ecules.

Keywords: co-crystal; crystal structure; hydrate; imidazolium; tetra­chlorido­zincate.

Figure 1

The mol­ecular structure of (I), showing the atom-labeling scheme. Non-hydrogen anisotropic displacement parameters are drawn at the 50% probability level.

Figure 2

The mol­ecular structure of (II), showing the atom-labeling scheme. Non-hydrogen anisotropic displacement parameters are drawn at the 50% probability level.

Figure 3

Partial packing diagram of (I), showing the water–tetra­chlorido­zincate chains. Only the tetra­chlorido­zincate anion and the water of hydration are shown.

Figure 4

Packing diagram of (I), showing the hydrogen-bonding scheme. Only H atoms involved in the inter­actions are shown.

Figure 5

A view of the hydrogen bonding in (II), showing the ring motifs. Only H atoms involved in the inter­actions are shown. Only the major contributor to the disorder model of the water mol­ecule is shown.

Figure 6

A second view of the hydrogen bonding in (II). Only H atoms involved in the hydrogen bonds are shown. Only the major contributor to the disorder model of the water mol­ecule is shown.

Figure 7

Projections of π-stacked mol­ecules. The mol­ecules are related by the symmetry transformations (I) −x + 1, −y + 1, −z + 1; (IIa) x, y, z; (IIb) x + 1, y − 1,z; (III) x, y, z + 1.