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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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02:34Structural Isomerism
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Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can...
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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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01:34Woodward–Hoffmann Selection Rules and Microscopic Reversibility
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Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
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02:52Stereoisomerism
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Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
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イリジウム (III) 複合体の自己組み立て可能な可逆的興奮状態変換による構造的リジメ化戦略
Xiangyu Liu1, Jing Liu2, Danlei Zhu1
1Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University Beijing 100084, P. R. China.
Journal of the American Chemical Society
|October 15, 2024
まとめ
研究者は,自己組み立てを使用して刺激反応性イリジウム (III) コンプレックスを作成する新しい方法を開発しました. これらの材料は異なる条件に晒されると色を変えて 複数の刺激に対応したデータ暗号化が可能になります
科学分野:
- 材料科学
- 写真化学
- 超分子化学
背景:
- 刺激に反応する色素材料は,外部の刺激で色を変えて,幅広い用途を見つけます.
- 移行金属複合体,特にイリジウム (III) 複合体は,構成と積み重ねによって影響される調節可能な興奮状態のため,クロミック材料にとって有望である.
- 多重刺激反応のための八面体イリジウム (III) 複合体における秩序ある積み重ねを達成することは困難である.
研究 の 目的:
- イリジウム (III) 複合体の興奮状態の可逆調節のための自己組み立てによる構造的硬化戦略を開発する.
- データ暗号化アプリケーションの様々な刺激下で,イリジウム (III) 複合体の色切り替えを実現する.
- 八面体イリジウム (III) 複合体で並ぶという難題を克服する.
主な方法:
- テトラキス (perfluorophenyl) -ボラート ([B (PhF5) 4]) カウンテリオンを持つカチオンイリジウム (III) 複合体の調製.
- カウンテリオンとイリジウム (III) カチオンの間の極性π相互作用を利用して,自己組み立てと構造的硬化を引き起こす.
- 集積状態における金属からリガンドへの電荷移転 (3MLCT) からリガンド中心の (3LC) 状態への興奮状態変換を調査する.
主要な成果:
- 構造的硬化により,3MLCT興奮状態の形状の変化が制限され,3LC興奮状態への変換が容易になった.
- 興奮状態の変換は,光発光スペクトルの54nmの青いシフト (黄色から空の青) を導いた.
- 低温,蒸気蒸気,およびデータの暗号化のための機械的な力に対して明確な反応を示す,開発されたイリジウム (III) 複合体.
結論:
- オクタエドール複合体の並び並びのための新しい戦略が成功裏に実装されました.
- この研究は,移行金属複合体の振る舞いを支配する光物理学的プロセスに関するより深い洞察を提供します.
- この研究は,高度な複数の刺激に反応するクロミック材料の設計に新しい視点を提供します.