Facile Synthesis Of Magnetic And Optically Active Nanoparticles Grafted With Helical Poly(phenyl Isocyanide)Arms And Their Application In Enantioselective Crystallization

In this manuscript,we report on the synthesis of hybrid Fe3O4 magnetic nanoparticles grafted with helical poly(phenyl isocyanide)(PPI)arms via both"grafting from" and "grafting onto“strategies.First,alkyne-Pd(Ⅱ)catalyst was anchored onto the surface of Fe3O4 magnetic nanoparticle,which initiated the polymerization of phenyl isocyanide led to the formation of expected hybrid magnetic nanoparticle with Fe3O4 in core and helical PPI as arms.When enantiopure phenyl isocyanide monomer bearing L-alanine ester pendant was used in the surface-initiated polymerization,the afforded hybrid nanoparticles exhibited highly optical activity due to the excess of one handed helicity of the PPI arms.Moreover,the hybrid magnetic nanoparticle can also be synthesized via "grafting onto" strategy.A triethoxysilanyl terminated single handed helical PPI bearing L-alanine ester pendants was prepared and grafted onto the surface of Fe3O4 nanoparticle.The generated hybrid magnetic nanoparticle showed high optical activity as revealed by circular dichroism(CD)and polarimetry.Thus,all the synthetic hybrid nanoparticles exhibited both magnetic character and optical activity.Taking advantage of these properties,the nanoparticles can be further used in enantioselective crystallization of racemic threonine.The enantiomeric excess(ee)of the crystalized enantiomer is up to 93%.Moreover,the nanoparticles can by recovered assisted by external magnetic field and reused for at least fourth times without significantly loss its enantioselectivity.