Hansen solubility parameters sphere calculations and thermodynamic model fitting of two novel copper complexes supported by bis(imino)pyridine ligands

Abstract

In this paper, two novel five-coordinated copper(II) metal complexes, [2,6-(ArN = CMe)2C5H3NCuCl2] (Ar = 2-EtC6H4, L1CuCl2; Ar = 4-EtC6H4, L2CuCl2), bearing bulky 2,6-bis[1-(2-ethylphenylimino)ethyl]pyridine ligands L1 (L1 = 2,6-(ArN = CMe)2C5H3N, Ar = 2-EtC6H4), 2,6-bis[1-(4-ethylphenylimino)ethyl]pyridine ligands L2 (L2 = 2,6-(ArN = CMe)2C5H3N, Ar = 4-EtC6H4) have been synthesized and characterized, and the thermodynamic properties of these complexes are reported in a variety of mono-solvents. The copper(II) metal complexes based on bis(imino)pyridine are widely used in catalysis, photoelectric material, biopharmaceuticals and other fields. In this paper, the solubility of L1 and L2 in four solvents, the solubility of L1CuCl2 in four solvents and the solubility of L2CuCl2 in five solvents were studied by static analysis. The solubility of these compounds was investigated in a certain temperature range to provide data to support the selection of optimal solvents for organic reactions, coating and crystallization separations. Hansen solubility parameters (HSPs) were used to explain the dissolution behavior of solutes and were found to be consistent with experimentally measured results. Moreover, the values of HSPs for L1CuCl2 and L2CuCl2 lacking Cu data were simulated by the Hansen Solubility Parameters in Practice (HSPiP) software, which allowed the prediction of solvents with good dissolution behavior. The values of total solubility parameter of Hildebrand (δ) for L1CuCl2 and L2CuCl2 are 24.5 and 23.0, respectively. Besides, solubility properties of L1CuCl2 and L2CuCl2 in two solvent mixtures at different percentages were predicted. In addition, seven thermodynamic models were used to correlate the solubility data. For L1 and L2, Polynomial models fit better with an average absolute relative deviation (ARD) less than 1 %; for L1CuCl2 and L2CuCl2, Polynomial model fits best (ARD < 1 %). In addition, the enthalpy–entropy compensation relationship in the dissolution process was analyzed by calculating the thermodynamic parameters of the substances, and the results showed that the dissolution process of L1 and L2 was an enthalpy-driven heat absorption process.