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

The nano-composites Fe(3)O(4)@SiO(2)@(–O(3)Si[(CH(2))(3)NH])P([double bond, length as m-dash]O)(NH-R(+)CH(CH(3))(C(6)H(5)))(2) (Fe(3)O(4)@SiO(2)@PTA(+)) and Fe(3)O(4)@SiO(2)@(–O(3)Si[(CH(2))(3)NH])P([double bond, length as m-dash]O)(NH-S(−)CH(CH(3))(C(6)H(5)))(2) (Fe(3)O(4)@SiO(2)@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. Fe(3)O(4), Fe(3)O(4)@SiO(2), Fe(3)O(4)@SiO(2)@PTA(+) and Fe(3)O(4)@SiO(2)@PTA(−) are regularly spherical with uniform shape and the average sizes of 17–20, 18–23, 36–47 and 43–52 nm, respectively.