迪乙烯二聚体,三聚体和四聚体的高效光环化:量子产量和反应动态
Teruaki Kaieda1, Seiya Kobatake, Hiroshi Miyasaka
1Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, and CREST, Japan Science and Technology Corporation, Higashi-ku, Fukuoka 812-8581, Japan.
Journal of the American Chemical Society
|February 28, 2002
概括
合成的多二甲基乙烯阵列在紫外线/可见光照射时呈现可逆色变. 增加的二甲基乙烯单位可以提高光循环的量子产量,这是由于高效的能量迁移.
科学领域:
- 有机化学 有机化学
- 摄影化学的使用.
- 材料科学 材料科学 材料科学
背景情况:
- 狄氏乙烯 (DTE) 化合物以其光色特性而闻名.
- 光色学涉及由光引起的可逆色变.
- 调整DTE属性对于开发先进光学材料至关重要.
研究的目的:
- 为了合成和表征多二甲基乙烯阵列.
- 为了研究数组长度对光环化量子产量的影响.
- 为了阐明增强光色性能背后的机制.
主要方法:
- 合成乙烯桥式多二甲基乙烯阵列 (二聚体,三聚体,四聚体).
- 在紫外线和可见光照射下对光染色性能进行评估.
- 对于光环化反应的量子产量确定.
- 皮秒激光光解和光脱极化研究.
主要成果:
- 合成的阵列在紫外线照射时显示可逆的紫蓝色变色,随着可见光消失.
- 光环化量子产量从0.21增加到0.40,随着DTE单位的增加 (1到4).
- 观察到有效的刺激能量从平行到反平行对应物的迁移证据.
结论:
- 多二甲基乙烯阵列提供可调节的光色特性.
- 增加的结合和能量迁移提高了这些阵列中的光循环效率.
- 这些发现有助于设计新型光响应材料.
相关概念视频
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.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
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
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
01:28Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
01:17Pericyclic Reactions: Introduction
Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...