含有光色二甲基乙烯的离子液体和N-异环碳化合物
Vivian Wing-Wah Yam1, Jason Ka-Wai Lee, Chi-Chiu Ko
1Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, PR China. wwyam@hku.hk
Journal of the American Chemical Society
|January 6, 2009
概括
研究人员开发了新的光色二甲基N-异环碳 (NHCs) 用于黄金,银和. 这些化合物表现出可逆光色行为和可调节的发光,使可光切换的含金属材料和催化剂成为可能.
科学领域:
- 有机金属化学 有机金属化学
- 材料科学 材料科学 材料科学
- 摄影化学的使用.
背景情况:
- 在有机金属化学中,N-异环碳 (NHCs) 是多功能联体.
- 迪亚利是众所周知的光色分子,在辐射时具有显著的结构变化.
- 将光色单元与NHC连接体结合在一起,为刺激响应材料提供了潜力.
研究的目的:
- 设计和合成含有阿尔杜恩戈类型的新型光色日利乙烯的N-异环碳 (NHCs).
- 研究这些NHC与金 (I),银 (I) 和 (II) 金属中心的协调化学.
- 探索由此产生的金属复合物的光色和发光特性.
主要方法:
- 用二甲功能化的伊米达盐的合成.
- 通过脱化形成N-异环碳.
- 与黄金 (I),银 (I) 和 (II) 前体复合.
- 使用NMR光谱学,质谱学和X射线晶体学进行表征.
- 光物理研究包括UV-Vis吸收,辐射光谱和光色切换实验.
主要成果:
- 成功合成和表征了新的光色NHC配体及其金属复合物.
- 在UV-Vis照射下显示可逆光色行为 (颜色和结构变化).
- 对复合体的开放式和封闭式的不同发光性质的观察.
- 与光环化和光环逆转相关的电子和形状变化的证据.
结论:
- 合成的二甲基乙烯-NHC配体及其金属复合物表现出有希望的光色和发光特性.
- 这些发现为开发新的光响应联结体和金属基材料开辟了道路.
- 潜在的应用包括可光开关的催化剂,传感器和具有可调节功能的智能材料.
相关概念视频
Photochemical 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
Thermal 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.
[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.
Thermal 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.
Aromatic Hydrocarbon Cations: Structural Overview
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 with both...
Removing one hydrogen from the intervening CH2 group with both...
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry
Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.


