在纳米级反应堆中对多态过渡的立体化学控制
Qi Jiang1, Chunhua Hu, Michael D Ward
1Molecular Design Institute, Department of Chemistry, New York University, 100 Washington Square East, New York, New York 10003-6688, USA.
Journal of the American Chemical Society
|February 2, 2013
概括
在纳米孔中形成的转移稳定的β-甘氨酸纳米晶体在高湿度下转化为α-甘氨酸. 氨基酸辅助剂可以通过阻止水进入关键晶体面来抑制这种相位过渡.
科学领域:
- 材料科学 材料科学 材料科学
- 晶体学 晶体学是指结晶学.
- 纳米技术纳米技术
背景情况:
- 甘氨酸是一种氨基酸,存在多种多态形式,包括转移稳定的β-甘氨酸和稳定的α-甘氨酸.
- 纳米限制可以改变结晶路径和多态稳定性.
- 阳极氧化 (AAO) 纳米孔为研究纳米晶体形成提供了受控的环境.
研究的目的:
- 为了研究AAO纳米孔中的甘氨酸结晶.
- 为了确定不同湿度下的β-甘氨酸纳米晶体的相位过渡行为.
- 探索氨基酸辅助剂在控制糖氨酸多态过渡中的作用.
主要方法:
- 在不同直径的AAO纳米孔内结晶甘氨酸.
- 用于结构分析的二维X射线微分歧.
- 控制湿度实验以诱导相位过渡.
- 在结晶过程中使用racemic和enantiopure氨基酸辅助剂.
主要成果:
- 在AAO纳米孔<200nm中形成的转移稳定的β-甘氨酸,[010]轴与孔孔方向对齐.
- 在90%的相对湿度下,β-甘氨酸纳米晶体转化为α-甘氨酸,并对[010]轴进行重新定位.
- 种族氨基酸辅助剂通过选择性地与{010}面结合,抑制了β向α转换.
- 乙酸辅助剂并没有阻止过渡,这表明立体选择性结合和获得水的重要性.
结论:
- 在AAO纳米孔中的β-甘氨酸的[010]轴方向与聚合物单体中的方向相似.
- 高湿度诱导从β-甘氨酸到α-甘氨酸的相位过渡,具有显著的分子重定位.
- 氨基酸辅助剂可以充当结晶修饰剂,通过对水分子进行固态阻碍来防止相位过渡.
- 氨基酸与特定晶体面的立体选择性结合对于控制纳米环境中的甘氨酸多态性至关重要.
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