离子相互作用和反应的光调制:在伊米达和伊米达之间进行可逆光转换
Takuya Nakashima1, Masako Goto, Shigekazu Kawai
1Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Journal of the American Chemical Society
|October 10, 2008
概括
研究人员开发了一种新型的光色系统,使得意达和意达盐之间的可逆转换成为可能. 这种可光切换系统控制化学反应,并表现出独特的光依赖性质,为材料科学开辟了新的途径.
科学领域:
- 材料科学 材料科学 材料科学
- 有机化学 有机化学
- 摄影化学的使用.
背景情况:
- 由于芳香度和电荷分布的差异,伊米达和伊米达离子具有不同的反应性概况.
- 通过外部刺激控制这些特性对于开发先进的功能材料至关重要.
研究的目的:
- 通过光辐射引入第一个imidazolium和imidazolinium盐之间的互转换系统.
- 为了研究一种新的4,5-dithiazolylimidazolium盐作为光色材料.
- 通过光诱导的结构变化来探索静电相互作用和化学反应的调制.
主要方法:
- 一种4,5-dithiazolylimidazolium盐的合成.
- 用紫外线和可见光照射进行可逆转换的光色学研究.
- 用光谱分析 (UV-Vis) 来研究溶和离子色素.
- 在甲氧化的存在下核友反应性的评估.
主要成果:
- 4,5-dithiazolylimidazolium盐在开放形式 (imidazolium) 和封闭形式 (imidazolinium) 之间展示了可逆的光转换.
- 封闭形式的伊米达呈现出显著的溶和离子色差 (吸收转移>80 nm),与开放形式的伊米达不同.
- 伊米达的形式显示出对核的增强反应性,使其成为光照反应系统,而伊米达的形式是惰性的.
结论:
- 光照射有效地控制着伊米达和伊米达状态之间的相互转换,调节它们的特性.
- 在imidazolinium形式中观察到的色差归因于光诱导的离子相互作用的变化.
- 开发的系统成功地展示了光控制的核友反应,突出了其在光响应化学中的潜力.
相关概念视频
01:26Photochemical Electrocyclic Reactions: Stereochemistry
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
Selection Rules: Photochemical Activation
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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.
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.
01:17Ion Exchange
Ion exchange chromatography separates charged molecules from a solution by reversibly exchanging them with mobile, or 'active', ions associated with the oppositely charged stationary phase. This method can be used to separate ions, soften and deionize water, and purify solutions. The polymers comprising the ion-exchange column are high-molecular-weight and chemically stable polymers, crosslinked to be porous and essentially insoluble. They are also functionalized with either acidic or basic...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:11Aryldiazonium Salts to Azo Dyes: Diazo Coupling
The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the para position.