...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Physical chemistry chemical physics: PCCP >Caging and solvent effects on the tautomeric equilibrium of 3-pyridone/3-hydroxypyridine in the ground state: a study in cyclodextrins and binary solvents
【24h】

Caging and solvent effects on the tautomeric equilibrium of 3-pyridone/3-hydroxypyridine in the ground state: a study in cyclodextrins and binary solvents

机译：笼罩和溶剂对基态3-吡啶酮/ 3-羟基吡啶的互变异构平衡的影响：环糊精和二元溶剂的研究

获取原文
获取原文并翻译 | 示例
   

获取外文期刊封面封底 >>

       
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The tautomeric equilibrium between 3-pyridone (3Py) and 3-hydroxypyridine (3HP) shows characteristic absorption peaks for the zwitterion form of 3Py in water that may be used as a probe of the hydrophobic nature inside macromolecules such as proteins and other biologically related systems. We studied this equilibrium in the ground state in aqueous cyclodextrins (CDs) and in binary solvent mixtures of 1,4-dioxane and water by absorption spectroscopy, and by ab initio calculations. Upon the addition of α-CD or β-CD to an aqueous solution of the 3Py/3HP system, the absorbance intensity of the zwitterion tautomer decreases with a concomitant increase in the intensity of the enol tautomer of 3HP. The results reflect the nature of the tautomeric equilibrium and point to the hydrophobic environment inside the CD cavities. The effect of inclusion is noticeably less in the case of α-CD. This is attributed to the small cavity size of α-CD which sustains only partial inclusion. Upon the addition of γ-CD, the intensity of the zwitterion tautomer slightly increased over that in water which is attributed to the direct interaction between the charged sides of the tautomer with the outer primary or secondary hydroxyls of the glycopyranose units of γ-CD. This interaction is a result of the large cavity size of γ-CD which does not support a stable complex. The largest caging effect was observed in 2,6-di-O-methyl-β-CD (DMβ-CD) which is an indication of a more hydrophobic environment around the guest. The large hydrophobicity of DMβ-CD is due to the presence of the two methyl groups in the β-CD derivative which reduce the amount of water inside the cavity upon encapsulation. In the binary mixtures of 1,4-dioxane and water, the change in the absorbance intensity of the enol and the zwitterion tautomers was analyzed quantitatively and three water molecules were found to solvate the polar centers of each tautomer. Ab initio calculations of the solvation of both tautomers by two and three water molecules were performed at the MP2/6-31++G(d,p) level. The calculations show that three water molecules are necessary to solvate the polar centers of each tautomer in a water network pattern. The results presented here suggest that the 3Py/3HP system represents a potentially useful new photophysical probe for supramolecular structures, particularly those involving inclusion.
机译：3-吡啶酮（3Py）与3-羟基吡啶（3HP）之间的互变异构平衡显示了3Py两性离子形式在水中的特征吸收峰，可以用作大分子内部疏水性探针，例如蛋白质和其他生物相关系统。我们通过吸收光谱法和从头算计算研究了环糊精（CD）水溶液中基态和1,4-二恶烷与水的二元溶剂混合物中的平衡状态。当将α-CD或β-CD添加到3Py / 3HP系统的水溶液中时，两性离子互变异构体的吸光度降低，同时3HP的烯醇互变异构体的强度随之增加。结果反映了互变异构平衡的性质，并指出了CD腔内的疏水环境。在α-CD的情况下，包含的影响明显较小。这归因于α-CD的小腔体尺寸，其仅维持部分夹杂物。加入γ-CD后，两性离子互变异构体的强度比水中的强度略有增加，这归因于互变异构体的带电侧与γ-CD的糖吡喃糖单元的外部伯羟基或仲羟基之间的直接相互作用。这种相互作用是由于γ-CD的腔尺寸较大而导致的，该尺寸不支持稳定的复合物。在2,6-二-O-甲基-β-CD（DMβ-CD）中观察到最大的笼罩效应，这表明客体周围的疏水环境更强。 DMβ-CD的大疏水性是由于β-CD衍生物中两个甲基的存在，它们在包封时减少了腔体内的水量。在1,4-二恶烷和水的二元混合物中，对烯醇和两性离子互变异构体的吸光度变化进行了定量分析，发现三个水分子可溶解每个互变异构体的极性中心。在MP2 / 6-31 ++ G（d，p）水平进行了两个和三个水分子对两个互变异构体的溶剂化的从头算。计算表明，需要三个水分子以水网络模式溶解每个互变异构体的极性中心。此处给出的结果表明3Py / 3HP系统代表了一种超分子结构（特别是涉及包涵体）的潜在有用的新型光物理探针。

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