Preparation Of Homochiral Organic-inorganic Hybrid Silicas

Helixity exists everywhere in nature. It is a hot topic to design and synthesis ofchiral materials in current research. Recently, many research groups are focusing oncontrolling the morphologies of the chiral aromatic ring bridged organic-inorganichybrid silicas which chirality can be identified in the circular dichroism (CD) spectra.Because these hybrid silicas exhibit chirality at molecular levels, they are potentiallyapplied in asymmetric catalysis and enantioseparation. It was reported by us that theycan be prepared through self-and external templating approaches. However, therelationship of their chirality at nano-and molecular levels has not been well-studied.Herein, organic-inorganic hybrid silicas with homochirality were prepared througha sol-gel transcription approach using the self-assemblies of chirallow-molecular-weight amphiphiles (LMWAs) as templates. Firstly, a series of chiralLMWAs derived from L-isoleucine were synthesized, which were characterized using IR,NMR, elemental analysis and CD. Secondly, aromatic ring bridged silicas wereprepared using the self-assemblies of the chiral LMWAs as the templates and aromaticorganicsilanes as the precursors under basic conditions. They were characterized usingscanning electron microscopy, transmission electron microscopy, X-ray diffraction andN2sorptions. It was found that the chirality of the hybrid silicas at nano-and molecularscales was not always same. It was proposed that the chiral hybrid silicas shown herewere suitable for application in asymmetric catalysis, enantioseparation and optics.