Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation

Abstract

The nano-composites Fe₃O₄@SiO₂@(–O₃Si[(CH₂)₃NH])P(O)(NH-R(+)CH(CH₃)(C₆H₅))₂ (Fe₃O₄@SiO₂@PTA(+)) and Fe₃O₄@SiO₂@(–O₃Si[(CH₂)₃NH])P(O)(NH-S(−)CH(CH₃)(C₆H₅))₂ (Fe₃O₄@SiO₂@PTA(−)) were prepared and used for the chiral separation of five racemic mixtures (PTA = phosphoric triamide). The separation results show chiral recognition ability of these materials with respect to racemates belonging to different families of compounds (amine, acid, and amino-acid), which show their feasibility to be potential adsorbents in chiral separation. The nano-composites were characterized by FTIR, TEM, SEM, EDX, XRD, and VSM. The VSM curves of nano-composites indicate their superparamagnetic property, which is stable after their use in the separation process. Fe₃O₄, Fe₃O₄@SiO₂, Fe₃O₄@SiO₂@PTA(+) and Fe₃O₄@SiO₂@PTA(−) are regularly spherical with uniform shape and the average sizes of 17–20, 18–23, 36–47 and 43–52 nm, respectively.