Lattice potential energies and thermochemical properties of crystalline complexes (1-CnH2n+1NH3)2CuCl4(s) (n = 10 and 11)

Abstract

The crystalline complexes (1-CnH2n+1NH3)2CuCl4(s) (n=10 and 11) were synthesized as new kinds of solid–solid phase change materials (SSPCMs). Crystal structures and chemical compositions of the two complexes have been characterized by X-ray single crystal diffraction technique, chemical analysis, and elementary analysis. Based on crystallographic data, the lattice potential energies and ionic volumes of the cations and the common anion of the two complexes were calculated. Molar enthalpies of dissolution of the two complexes with various values of molality were measured in double-distilled water via an isoperibol solution-reaction calorimeter at T=298.15K. On the basis of the Pitzer electrolyte solution theory, the molar enthalpies of dissolution of the two complexes at infinite dilution were calculated to be ΔsHm∞(C10H21NH3)2CuCl4(s)=(49.916±1.138)kJ·mol−1 and ΔsHm∞(C11H23NH3)2CuCl4(s)=(62.690±0.769)kJ·mol−1, and the sums of Pitzer parameters were obtained. In addition, with the values of molar enthalpies of dissolution at infinite dilution (ΔsHm∞) and other auxiliary thermodynamic data, the enthalpy change of the dissociation of [CuCl4]2−(g) for the reaction [CuCl4]2−(g)→Cu2+(g)+4Cl−(g) was obtained by designing a thermochemical cycle.