Steric and Temperature Control of Enantiopurity of Chiral Mesoporous Silica

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• 作者：Huibin Qiu ; Shuguang Wang ; Wanbin Zhang ; Kazutami Sakamoto ; Osamu Terasaki ; Yoshihisa Inoue ; Shunai Che
• 刊名：Journal of Physical Chemistry C
• 出版年：2008
• 出版时间：February 14, 2008
• 年：2008
• 卷：112
• 期：6
• 页码：1871 - 1877
• 全文大小：559K
• 年卷期：v.112,no.6(February 14, 2008)
• ISSN：1932-7455

文摘

To elucidate the factors and mechanisms that control the chiral mesoporous silica (CMS) formation, weemployed a series of chiral amphiphilic molecules derived from nine different amino acids as templates andquantitatively investigated the effects of the substituent attached to the chiral center of amino acid upon CMSsynthesis at various temperatures. The enantiomeric excess (ee) of the CMS obtained was a critical functionof both the substituent's steric bulk and the temperature, and eventually exceeded 90% ee by performing theCMS synthesis at 288 K in the presence of amphiphilic N-palmitoyl-Phe or Met. The temperature dependencestudy of the product's ee not only gave the high ee's but also enabled us to determine the differential enthalpy(H) and entropy (S) changes for antipodal CMS formation, which simultaneously increased withincreasing steric bulk of the amino acid's substituent, indicating their critical roles in determining the CMS'senantiopurity. The present results also indicate that the CMS synthesis is a convenient tool for taking a snapshotof an average image of the dynamically fluctuating supramolecular aggregates with quantitative information(ee).