structural characterization of two tetrachloridozincate salts of 4-carboxy-1h-imidazol-3-ium: a salt hydrate and a co-crystal salt hydrate

Imidazole-containing compounds exhibit a myriad of pharmacological activities. Two tetrachloridozincate salts of 4-carboxy-1H-imidazol-3-ium, ImHCO2H+, are reported. Bis(4-carboxy-1H-imidazol-3-ium) tetrachloridozincate monohydrate, (C4H5N2O2)2[ZnCl4]·H2O, (I), crystallizes as a monohydrate salt, while bis(4-carboxy-1H-imidazol-3-ium) tetrachloridozincate bis(1H-imidazol-3-ium-4-carboxylato) 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-carboxylate, ImHCO2, one tetrachloridozincate anion and one water molecule 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 tetrachloridozincate anion, resulting in interconnected chains of anions joined by water molecules.