trans-(1R,2R)-Diaminocyclohexane-functionalized mesoporous organosilica spheres as chiral stationary phase

The bifunctionalized mesoporous organosilica spheres with trans-(1R,2R)-diaminocyclohexane (DACH) in the pore were synthesized and their application as chiral stationary phase in high-performance liquid chromatography (HPLC) was demonstrated. Bifunctionalized mesoporous organosilica spheres with narrow particle size distribution of 5–7 μm were prepared by the co-condensation of N-[3-(triethoxysilyl)propyl]-trans-(1R,2R)-diaminocyclohexane (Mpropyl) with 1,2-bis(trimethoxysilyl)ethane (BTME) in basic medium using octadecyltrimethylammonium chloride (C18TACl) as structural directing agent and ethanol as co-solvent. The morphologies of the bifunctionalized mesoporous organosilicas were sensitive to the molar fraction of Mpropyl. At higher Mpropyl/BTME molar ratio, the bifunctionalized organosilica spheres with ordered mesoporous structure can be formed in a wide range of synthetic conditions. When the molar percent of Mpropyl/(Mpropyl + BTME) is less than 20, the formation of spheres could be hardly observed. The structural order of the materials mainly depends on the base concentration and Mpropyl/BTME molar ratio in the initial sol mixture. A column packed with the bifunctionalized mesoporous organosilica spheres exhibits higher selectivity and resolution for racemic amino acids than that packed with DACH-SiO2 prepared by conventional post-synthesis grafting method.