Solid–Liquid Equilibrium of TKX-50 in Three Binary Solvents: Experiments, Correlation, Thermodynamic Analysis, Hansen Solubility Parameter and Molecular Simulation

The solubility of dihydroxylammonium 5,5’-bistetrazole-1,1’-diolate (TKX-50) in three binary mixed solvents (ethanol + H₂O, DMSO + H₂O, and DMF + H₂O) was determined using a laser dynamic monitoring technique at various temperatures ranging from 293.15 to 333.15 K and at atmospheric pressure (P = 0.1 MPa). The results show that the solubility of TKX-50 in mixed solvents increases with temperature, decreases with increasing water content in DMSO + H₂O and DMF + H₂O, and increases with increasing water content in ethanol + H₂O. The experimental solubility data were used for correlation analysis using the Modified Apelblat equation, van’t Hoff equation, CNIBS/R-K equation, and Jouyban–Acree–Apelblat equation. All of these models yielded satisfactory results in binary solvents. Subsequently, the effects of hydrogen bonding, solvent polarity, and intermolecular interaction forces on the dissolution behavior of TKX-50 were analysed using Hansen solubility parameter (HSPs), Hirshfeld surface analysis (HS), and molecular electrostatic potentials (MEPs). In addition, the thermodynamic properties enthalpy, entropy, and Gibbs energy were calculated and discussed based on experimental data.