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Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

2.2K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
2.2K
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

2.9K
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
2.9K
[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement01:21

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement

3.3K
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
3.3K
Crystal Field Theory - Octahedral Complexes02:58

Crystal Field Theory - Octahedral Complexes

30.5K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
30.5K
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

3.6K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
3.6K
Crystal Field Theory - Tetrahedral and Square Planar Complexes02:46

Crystal Field Theory - Tetrahedral and Square Planar Complexes

48.0K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
48.0K

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Updated: Jan 11, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
10:35

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Published on: May 29, 2018

9.1K

在拓化学光异构化中的晶体包装-轨迹相关性.

Bryan Po-Wen Chen1, Chao-Ping Hsu2,3, Joseph Jen-Tse Huang2

  • 1Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Da'an District, Taipei, 10617, Taiwan.

Angewandte Chemie (International ed. in English)
|November 10, 2025
PubMed
概括

固态光异构化在密集的晶体中是可能的,如果存在足够的固态自由度. 这项研究揭示了局部自由体积和光响应之间的相关性,使可光切换材料的合理设计成为可能.

关键词:
照片染色主义是什么?摄影异构化 (Photoisomerization) 是一个过程.一个单晶的晶体.拓化学 是一种拓化学.

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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
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Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method

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相关实验视频

Last Updated: Jan 11, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
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科学领域:

  • 材料科学 材料科学 材料科学
  • 摄影化学的使用.
  • 晶体学 晶体学是指结晶学.

背景情况:

  • 固态光异构化通常需要松散的结构来实现分子灵活性.
  • 了解晶体包装和光反应性之间的关系对于设计新材料至关重要.

研究的目的:

  • 为了研究沙利基化衍生物的固态光异构化.
  • 建立一个结构-属性关系,将分子包装与光色反应联系起来.
  • 开发固态光反应的预测模型.

主要方法:

  • 基化衍生物的合成和结晶.
  • 用X射线晶体学分析晶体包装和π-π堆叠.
  • 沿着异构化路径量化可访问体积的量化.
  • 开发基于晶体结构的描述符 ("脚踏空间").

主要成果:

  • 几个密集的沙利西尔化晶体表现出光色的行为.
  • 在局部自由体积和光响应之间发现了强烈的相关性.
  • 确定了固态光反活性的一个关键值.
  • 包装图案 (滑动与共同面部堆叠) 影响光化学路径.

结论:

  • 拓化学光异构化受晶体包装和局部自由体积的控制.
  • "踏板空间"描述符有效地预测了固态光反应性.
  • 晶体工程原理可以指导可光切换材料的in silico设计.
  • 这种方法有助于成本效益高的响应式光电子系统的开发.