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.