...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >A new polymorph of ortho-ethoxy-trans-cinnamic acid: single-to-single-crystal phase transformation and mechanism
【24h】

A new polymorph of ortho-ethoxy-trans-cinnamic acid: single-to-single-crystal phase transformation and mechanism

机译：一种新的正乙氧基-肉桂酸多晶型物：单晶至单晶相变及其机理

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The alpha-polymorph of ortho-ethoxy-trans-cinnamic acid (OETCA) undergoes a reversible single-crystal-to-single-crystal phase transformation at 333 K. The new high-temperature polymorph (alpha'-OETCA) is stable between 333 and 393 K with three molecules in the asymmetric unit (Z' 3), space group P(1) over bar. Unlike the other polymorphs (and solvate) of OETCA recently reported, two of the molecules in alpha'-OETCA deviate significantly from planarity. This conformational change results in the corrugated sheet-type structure of alpha'-OETCA. The sheets are made up of ribbons, each composed of R-2(2)(8) hydrogen-bonded pairs (via the -COOH groups), which are further connected by CH...O interactions. When exposed to UV radiation the alpha'-OETCA polymorph can be stabilized below 333 K with ca 8% of the monomer converted into the photodimer. The crystal structures of alpha'-OETCA are reported at two temperatures above the phase transition point (at 345 and 375 K) as well as the stabilized forms at 173 and 293 K. A mechanism for the phase transition involving a cooperative conformational transformation coupled with a shift of layers of OETCA molecules is proposed. The alpha'-OETCA polymorph is also an example of a cinnamic acid derivative where two different potentially photoreactive environments exist in one crystal in which each unit cell has two non-centrosymmetric predimer sites and one centrosymmetric predimer site.
机译：正乙氧基-肉桂酸（OETCA）的α多晶型物在333 K处经历了可逆的单晶至单晶相变。新的高温多晶型物（α'-OETCA）在333 K之间稳定和393 K，其中三个分子位于不对称单元（Z'3）中，上方为空间群P（1）。与最近报道的OETCA的其他多晶型物（和溶剂化物）不同，α'-OETCA中的两个分子与平面度明显不同。这种构象变化导致了α'-OETCA的波纹片状结构。薄板由碳带组成，每个碳带由R-2（2）（8）氢键对组成（通过-COOH基团），并通过CH ... O相互作用进一步连接。当暴露于紫外线辐射下时，α'-OETCA多晶型物可以稳定在333 K以下，并且约有8％的单体转化为光二聚体。据报道，α'-OETCA的晶体结构在高于相变点的两个温度下（分别在345和375 K处）以及在173和293 K处具有稳定的形式。相变的机理包括协同构象转化和提出了OETCA分子层的移位。 α'-OETCA多晶型物也是肉桂酸衍生物的一个例子，其中一个晶体中存在两种不同的潜在光反应性环境，其中每个晶胞具有两个非中心对称的预聚物位点和一个中心对称的预聚物位点。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号