ABSTRACT
The keto-enol tautomerism of avobenzone (AVO) is pivotal to its photostability, influenced by microenvironmental factors, such as, the type of solvent and complexation with macrocyclic compounds. This study explores the effect of host-guest complexation on AVO photostabilization, employing cucurbit[7]uril (CB[7]) and ß-cyclodextrin (ß-CD) to form inclusion complexes. CB[7] exhibits a higher affinity to the keto form of AVO, a UVC radiation absorber. The complexed keto form facilitates the regeneration of the enol form, reducing skin permeation. Spectroscopic and thermal analyses confirm 1 : 1 AVO-CB[7] and AVO-ß-CD complex formation. Computational and MD simulations show that host-guest complex is favored over isolated AVO and ß-CD or CB[7] molecules by 95-125 kJ mol-1, depending on the presence of implicit solvent. Both macrocycles enhance AVO photostabilization in aqueous environments, with CB[7] displaying greater selectivity for the keto form, while ß-CD shows ethanol concentration-dependent binding.
ABSTRACT
We report a new synthesis of the water-soluble compound 1,3,5-trihydroxy-2,4,6-trimethylsulfonic acid (1), which exists in two tautomeric forms (60 : 40::enol%:keto%) and can be used as a proton conductor. Quantum chemical calculations show the importance of intramolecular hydrogen bonding and the presence of implicit MeOH solvent on the relative stabilities of the tautomers. 1 complexes with lanthanides through its sulfonato groups and forms a layered cage-like structure with one intramolecular and two intermolecular hydrogen bonds.
ABSTRACT
Solid-state studies of C-butyl-resorcin[4]arene with pregabalin (Lyrica, Nervalin) in nitrobenzene yielded a cocrystal of C-butyl-resorcin[4]arene with 4-isobutylpyrrolidone-2. A combined experimental and quantum chemical investigation was implemented to further our understanding of the factors affecting the conversion process.