• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >Neutral and ionic hydrogen bonding in schiff bases
【24h】

Neutral and ionic hydrogen bonding in schiff bases

机译：席夫碱中的中性和离子氢键

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

Low-temperature, high-resolution X-ray studies of charge distributions in the three Schiff bases, the dianil of 2-hydroxy-5-methylisophthaldehyde, 3,5-dinitro-N-salicylidenoethylamine and 3-nitro-N-salicylidenocyclohexylamine, have been carried out. These structures exhibit interesting weak interactions, including two extreme cases of intramolecular hydrogen bonds that are ionic N~+ - H…O~- and neutral O-H…N in nature. These two types of hydrogen bond reflect differences in geometrical parameters and electron density distribution. At the level of geometry, the neutral O-H…N hydrogen bond is accompanied by an increase in the length of the C(1)-O(1) bond, opening of the ipso-C(1) angle, elongation of the aromatic C-C bonds, shortening of the C(7)-N(2) bond and increased length of the C(1)-C(7) bond, relative to the ionic hydrogen bond type. According to the geometrical and critical point parameters, the neutral O-H…N hydrogen bond seems to be stronger than the ionic ones. There are also differences between charge density parameters of the aromatic rings consistent with the neutral hydrogen bond being stronger than the ionic ones, with a concomitant reduction in the aromaticity of the ring. Compounds with the ionic hydrogen bonds show a larger double-bond character in the C-O bond than appears in the compound containing a neutral hydrogen bond; this suggests that the electronic structure of the former pair of compounds includes a contribution from a zwitterionic canonical form. Furthermore, in the case of ionic hydrogen bonds, the corresponding interaction lines appear to be curved in the vicinity of the hydrogen atoms. In the 3-nitro-N-salicylidenocyclohexylamine crystal there exists, in addition to the intramolecular hydrogen bond, a pair of intermolecular O…H interactions in a centrosymmetric dimer unit.
机译：低温，高分辨率X射线研究了三个席夫碱（2-羟基-5-甲基异乙醛，3,5-二硝基-N-水杨基亚乙基胺和3-硝基-N-水杨基环己胺）的二胺的电荷分布进行了。这些结构表现出有趣的弱相互作用，包括分子内氢键的两种极端情况，即离子性的N〜+-H…O〜-和中性的O-H…N。这两种类型的氢键反映了几何参数和电子密度分布的差异。在几何水平上，中性OH…N氢键伴随着C（1）-O（1）键长度的增加，ipso-C（1）角的打开，芳族CC的延长键，相对于离子氢键类型，C（7）-N（2）键的缩短和C（1）-C（7）键的长度增加。根据几何和临界点参数，中性的O-H…N氢键似乎比离子键强。芳香环的电荷密度参数之间也存在差异，这与中性氢键强于离子键相一致，同时环的芳香性降低。具有离子氢键的化合物与具有中性氢键的化合物相比，在C-O键中显示出更大的双键特性。这表明前一对化合物的电子结构包括两性离子规范形式的贡献。此外，在离子性氢键的情况下，相应的相互作用线似乎在氢原子附近弯曲。在3-硝基-N-水杨基亚环己基胺晶体中，除了分子内氢键外，在中心对称的二聚体单元中还存在一对分子间的O…H相互作用。

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