A combined experimental and theoretical study on p-sulfonatothiacalix[4]arene encapsulated sulisobenzone

Sunscreen ingredients such as sulisobenzone (SBZ) have the tendency to degrade when exposed to UV-radiation, which becomes major problem for their further development and application in the cosmetic industry. Host-guest inclusion complexation could be a promising strategy to address this issue. A new inclusion system of SBZ with p-sulfonatothiacalix[4]arene (TSC4X) was fabricated, and its binding behaviour both in solution and the solid state has been investigated by UV-visible spectroscopy, H-1 NMR, DSC, ESI-MS and FT-IR spectroscopy. The 1 : 1 stoichiometry of the inclusion complex was confirmed by Job's plot and mass spectrometry. TSC4X displayed a strong affinity for SBZ and the binding process was found to be thermodynamically feasible. FT-IR and H-1 NMR spectroscopic studies demonstrated that the unsubstituted aromatic moiety of SBZ is inserted into the cavity of TSC4X, which is in accordance with the molecular docking study. The aqueous solubility, photostability and thermal stability of SBZ were improved on complexation with TSC4X. The molecular docking study depicted the most feasible conformation of the inclusion complex with the lowest binding energy.