Preferential solvation of sunitinib malate (STM) was investigated in the binary mixtures of water, ethanol, ethylene glycol (EG), and propylene carbonate (PC) solvents at 298.15 K. Similar to its pharmaceutical formulation steps, dimethyl sulfoxide (DMSO) was used as the base solvent during our experiments. Bosch–Rose model was utilized to estimate the electronic transition energies, ET, and other preferential solvation parameters, demonstrating solute–solvent and solute–solute interactions. Shifting λmax situation with respect to the dielectric constant of the pure solvents was carefully monitored indicating that STM had the lowest λmax in water and PC among HBD and HBA solvents, respectively. Moreover, ET showed positive deviation with respect to ideality for ethanol–EG, ethanol–PC, and ethanol–DMSO binary systems while negative deviation was obtained for the others which was explainable based on the model assumptions. According to the results, STM molecules preferred to be solvated by PC, ethanol, EG, and DMSO solvent molecules rather than water in the binary mixtures of the aforementioned solvents, meaning that the presence of water in the cybotactic region is least probable compared to the others. Based on the local mole fractions, the abundance of pure solvents and/or complex solvent molecules in the cybotactic region around the solute was discussed in detail, illustrating the specific and non-specific interactions between solute and solvent molecules.
