• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >The Coumarin-Dimer Spring-The Struggle between Charge Transfer and Steric Interactions
【24h】

The Coumarin-Dimer Spring-The Struggle between Charge Transfer and Steric Interactions

机译：香豆素 - 二聚体弹簧 - 电荷转移和空间相互作用之间的斗争

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 synthesis of a weakly coupled, strongly polarized coumarin dimer has been achieved for the first time. The three-step strategy comprises the Skatteb?l formylation followed by the Knoevenagel reaction and the formation of a tertiary amide by using a peptide-type procedure. The molecule consists of two different coumarin moieties: One is a classical donor-acceptor system and the second one possesses a weaker amide donor at the 7-position. The polarized coumarin dimer can form an electronically conjugated structure possessing an electric dipole larger than that of 7-(dimethylamino)coumarin-3-carboxylic acid. The limited flexibility of the inter-coumarin connection results in stable conformers of different electric dipole moments and complex photophysics. In the solid state, this compound has a strongly bent conformation with the two coumarin units forming an angle of around 748. In solution, two conformers are in equilibrium. The existence of the molecule as two conformers in the ground state has been confirmed by optical studies, and further corroborated by molecular calculations. The fluorescence spectra possess a unique feature: A chargetransfer band (ca. 550 nm) is visible only in nonpolar or weakly polar solvents. Optical spectroscopy studies coupled with molecular calculations allowed us to rationalize this phenomenon: The large amplitude of intramolecular motions is responsible for the conformational isomerization as well as producing a conical intersection between the potential energy surfaces of the excited singlet state and the ground state, which opens an internal conversion channel that effectively competes with the fluorescence of the conformers.
机译：首次实现了弱偶联强度偏振的香豆素二聚体的合成。三步策略包括Skatteb？L型甲酰化，然后通过使用肽型方法进行knoevenagel反应和叔酰胺的形成。分子由两种不同的香豆素部分组成：一个是古典供体 - 受体系统，第二个是在7位的酰胺供体中具有较弱的酰胺供体。偏振香豆素二聚体可以形成具有大于7-（二甲基氨基）香豆素-3-羧酸的电偶极子的电子共轭结构。香豆素间连接的有限灵活性导致不同电偶极矩和复杂的光药的稳定塑造。在固态中，该化合物具有强烈弯曲的构象，与形成大约748左右的香豆素单位。在溶液中，两个塑形剂在平衡。通过光学研究证实了作为地面状态中的两个塑壳的分子的存在，并通过分子计算进一步证实。荧光光谱具有独特的特征：只能在非极性或弱极性溶剂中可见木炭转换带（CA.550nm）。与分子计算相结合的光学光谱研究使我们能够合理化这种现象：大的分子内运动的幅度是构象异构化的负责，以及在打开的激发单态和地位的潜在能量表面之间产生锥形交叉点，其打开内部转换通道，有效地与塑料的荧光竞争。

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