Solubility behavior and solvation effect of a photomechanical molecular crystal trans-4-chlorocinnamic acid in twelve neat solvents at temperatures from 283.15 to 323.15 K

Solubility of trans-4-chlorocinnamic acid as a photomechanical molecular crystal material in twelve pure solvents (water, ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, acetonitrile, 1,4-dioxane, acetone, methyl acetate and ethyl acetate) were measured from 283.15 to 325.15 K at 101.2 kPa. The results showed that the trans-4-chlorocinnamic acid solubility increased with the temperature, the order is: 1,4-dioxane > acetone > n-butanol > ethanol > n-propanol > isopropanol > isobutanol > methanol > methyl acetate > ethyl acetate > acetonitrile > water. Powder X-ray diffraction pattern (PXRD) and differential scanning calorimetry (DSC) were used to identify and characterize the equilibrated solid phase samples. The solubility behavior and the solute–solvent interaction of trans-4-chlorocinnamic acid in each selected mono-solvent were explored by the empirical solvents polarity parameter (E_T(30)), hydrogen bonding, cohesive energy density, molecular structure, and Hansen solubility parameters (HSPs). In addition, the experimental solubility data were correlated by the modified Apelblat model and Yaws model, and the fitting results of this models were all satisfactory. The intermolecular forces were determined through molecular simulations, including Hirshfeld surface (HS) and Molecular Electrostatic Potential Surface (MEPS) analysis. The results showed that hydrogen bond can be formed between trans-4-chlorocinnamic acid and the selected solvents, which can help to further explain the dissolution behavior of trans-4-chlorocinnamic acid in the solvents.