符合形态的异质性控制了五烯-二烯-四烯二二中的电荷转移路径
Aleesha George1, David C Bain1, Kanad Majumder2
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, 14850, USA.
概括
分子构造障碍决定了捐赠者-接受者系统中的放松路径. 平面形式显示快速的电荷转移,而扭曲的形式显示长寿命状态,影响光电子应用.
科学领域:
- 摄影化学的使用.
- 分子光谱学 分子光谱学
- 材料科学 材料科学 材料科学
背景情况:
- 了解分子构造障碍对于设计高效的供体-接受体系统至关重要.
- 分子内电荷转移 (ICT) 动态对分子结构和环境高度敏感.
研究的目的:
- 为了研究形状异质性对共价连接的供体-受体二中分子内电荷转移 (ICT) 的影响.
- 为了阐明同一分子内的不同适合体如何导致不同的光物理放松路径.
主要方法:
- 使用激发能量依赖的短暂吸收光谱学.
- 在各种溶剂中采用光发光谱学.
- 分析了一个共连接的捐赠者-接受者二 (P-D).
主要成果:
- 稳定平面形态体表现出超快速的分子内孔转移,形成短暂的,黑暗的电荷转移状态从带边激发.
- 在更高的能量下激发的不稳定的扭曲适合体导致了长期存在的发射电荷转移状态.
- 证明单个分子内的构造变化导致不同的放松动态.
结论:
- 形态异质性显著影响分子系统中的电荷转移路径和激发状态寿命.
- 对光电子产品的分子捐赠-接受系统的合理设计需要仔细考虑构造性障碍.
- 这些发现突显了研究具有多样化的构造景观的分子二次体对于先进应用的重要性.
相关概念视频
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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
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01:26Thermal and Photochemical Electrocyclic Reactions: Overview
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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.
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01:18Aromatic Hydrocarbon Cations: Structural Overview
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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...
Removing one hydrogen from the intervening CH2 group...
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01:17Thermal Electrocyclic Reactions: Stereochemistry
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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.
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Due to the absence of continuous...
Due to the absence of continuous...
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01:28Stability of Conjugated Dienes
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Introduction
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A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
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