Solubility determination and thermodynamic analysis of organic zinc supported by β-diimine ligands in pure solvents

In this work, a static analysis method was used to determine the solubility data of β-diimine ligand (1) (L₁ = HC(CMeNAr)₂, Ar = 2,6-Me₂C₆H₃), and organic zinc compounds: L₁ZnEt (2), L₂ZnEt (3) (L₂ = HC(CMeNAr)₂, Ar = 2,6-ⁱPr₂C₆H₃) in six pure solvents (methanol, ethanol, n-hexane, toluene, ether, dichloromethane, tetrahydrofuran) under nitrogen atmosphere. Experimental data are crucial for optimizing the purification, recrystallization process and the design of homogeneous catalysis for compounds 1, 2, and 3 in the industry. Six common thermodynamic models were utilized to correlate the experimental solubility data: Apelblat model, Polynomial empirical equation, λh model, Yaws model, NRTL model and Scatchard-Hildebrand activity coefficient model. These thermodynamic models were evaluated by average absolute relative deviation (AARD) to come to the best fitting model. Among them, the Polynomial empirical equation and the Scatchard-Hildebrand activity coefficient model had wide applicability, and the average AARD was <1. For compounds 1 and 3, Hirshfeld surface analysis was utilized to study the intermolecular interaction. The simulation results showed that H···H contact was obviously predominant in all contact interactions. In addition, apparent thermodynamic functions were derived. Results showed that the dissolution process was entropy increasing and endothermic under the experimental conditions, and the difference in solubility could be explained by spontaneous energy.