Crystal Structures, Lattice Potential Energies, and Thermochemical Properties of Crystalline Compounds (1-CnH2n+1NH3)2ZnCl4(s) (n = 8, 10, 12, and 13)

As part of our ongoing project involving the study of (1-CnH2n+1NH3)2MCl4(s) (where M is a divalent metal ion and n = 8–18), we have synthesized the compounds (1-CnH2n+1NH3)2ZnCl4(s) (n = 8, 10, 12, and 13), and the details of the structures are reported herein. All of the compounds were crystallized in the monoclinic form with the space group P21/n for (1-C8H17NH3)2ZnCl4(s), P21/c for (1-C10H21NH3)2ZnCl4(s), P21/c for (1-C12H25NH3)2ZnCl4(s), and P21/m for (1-C13H27NH3)2ZnCl4(s). The lattice potential energies and ionic volumes of the cations and the common anion of the title compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the four compounds at various molalities were measured at 298.15 K in the double-distilled water. According to Pitzer’s theory, molar enthalpies of dissolution of the title compounds at infinite dilution were obtained. Finally, using the values of molar enthalpies of dissolution at infinite dilution (ΔsHm∞) and other auxiliary thermodynamic data, the enthalpy change of the dissociation of [ZnCl4]2–(g) for the reaction [ZnCl4]2–(g)→ Zn2+(g) + 4Cl–(g) was obtained, and then the hydration enthalpies of cations were calculated by designing a thermochemical cycle.