Preparation and evaluation of two chiral stationary phases based on imidazolyl-functionalized bromoethoxy pillar[5]arene-bonded silica

Chiral pillar[5]arene-based mesoporous silica, an emerging class of chiral structure, possesses excellent characteristics such as abundant chiral active sites, encapsulated cavity and excellent chiral modification, which make them a promising candidate as new chiral stationary phases (CSPs) in enantioseparation. In this study, two imidazole-containing (S)-1-(4-phenyl-1H-imidazol-2-yl)ethanamine and (S)-Histidinol were respectively modified to bromoethoxy pillar[5]arene-bonded silica to construct new chiral stationary phases (sPIE-BP5-Sil and sHol-BP5-Sil) for the separation and analysis of enantiomers. The separation conditions such as mobile phase composition, flow rate and temperature were optimized. Under optimal conditions, both sPIE-BP5-Sil and sHol-BP5-Sil showed good separation performance for different types of enantiomers. Interestingly, sPIE-BP5-Sil and sHol-BP5-Sil showed better enantioselectivity for chiral aromatic compounds and chiral aliphatic compounds, respectively. This enantioseparation result was closely related to the presence of additional aromatic rings and abundant hydroxyl groups in the side chains of the two chiral groups. In addition, the enantioseparation process was further studied by molecular docking simulation. Therefore, this work provided a new strategy for the preparation and application of imidazolyl-derived pillar[5]arene-based chiral stationary phases, which can be efficiently used for screening and separating enantiomers.