関連する概念動画
01:26Photochemical Electrocyclic Reactions: Stereochemistry
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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
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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01:34The Z-Scheme of Electron Transport in Photosynthesis
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The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of water molecules to produce oxygen. However, oxidation of water molecules is a thermodynamically unfavorable reaction and requires a strong oxidizing agent. This is accomplished by the first product of light reactions: oxidized P680 (or P680+), the most powerful oxidizing agent known in biology. The oxidized P680 that acquires an electron from the...
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01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
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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.
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01:29The Photochemical Reaction Center
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Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
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01:17Thermal Electrocyclic Reactions: Stereochemistry
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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.
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フルレンベースのダイアドのレドックス状態を調節することによって,光誘導電子移転方向の局所的な切り替え
Yongqiang Chai1,2, Xiaolong Liu1, Bo Wu1
1Beijing National Laboratory for Molecular Sciences, Key Laboratory of Molecular Nanostructure and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Journal of the American Chemical Society
|February 8, 2020
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PubMed で要約を見る
まとめ
研究者らは,交換可能な電子移転を持つ新しいフルレンベースのドナー-受容体ダイアードを開発しました. この突破は,高度な分子エレクトロニクスのための調節可能な分子光ダイオード動作を可能にします.
科学分野:
- 材料科学
- 超分子化学
- 写真化学
背景:
- フラーレン基のドナー-受容体 (DA) ダイアッドは分子電子工学にとって極めて重要です.
- 光誘発電子伝送 (PET) の方向を制御することは,デバイスの機能の鍵です.
研究 の 目的:
- 新しいフルレンベースのDA二酸化物,Sc3N@C80-PTZとC60-PTZを合成し,研究する.
- リドックス状態を調節することにより,切り替え可能な光誘導電子移転方向を示す.
- 分子フォトダイオードのような 行動の可能性を探るためだ
主な方法:
- Sc3N@C80-PTZとC60-PTZダイアードの合成
- 暫定吸収 (TA) スペクトロスコーピーを用いた詳細な光物理的調査.
- 実験結果を裏付けるための理論的計算
主要な成果:
- 中性ダイアードで PTZ から Sc3N@C80 への還元電子移転が確認された.
- PTZの部分の可逆性酸化を観察した.
- Sc3N@C80 から PTZ 根幹カチオンへの酸化電子移転が実証され,メタステーブルな電荷移転状態を形成する.
- このCT状態はC60- PTZ+二酸化物では観察されなかった.
結論:
- フルレンの二酸化物を使って,最初の局所調節可能な分子光ダイオードのような振る舞いを達成した.
- 切り替え可能な電子伝送方向は,分子電子装置に新しい可能性を提供します.
- この発見は,フルレンベースの DA 結合物の先進的な応用への道を開く.