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01:26Photochemical Electrocyclic Reactions: Stereochemistry
1.8K
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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01:19Complexation Equilibria: The Chelate Effect
525
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
525
03:02Colors and Magnetism
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Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
11.7K
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.1K
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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00:43Complexometric Titration: Ligands
965
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
965
01:58Cooperative Allosteric Transitions
7.9K
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
7.9K
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マルチコンポーネントランタニド・オーガニック・アセンブリにおけるエキサイテッド・マルチメディアド・スーパモレキュラー・アップコンバージョン
Xiao-Fang Duan1,2, Li-Peng Zhou1, Hao-Ran Li1
1State Key Laboratory of Structural Chemistry, CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, P. R. China.
Journal of the American Chemical Society
|October 16, 2023
まとめ
研究者は,ユニークなアップコンバージョン (UC) 性質を示す新しいランタニド有機複合体を開発した. この新しい戦略は,強化された光機能のためのエキサイテッド-マルチプレート状態を利用することによって,調整可能なUC材料を可能にします.
科学分野:
- 材料科学
- 光学について
- 化学について
背景:
- アップコンバージョン (UC) は,広範なアプリケーションを持つ反ストークス光学プロセスです.
- 既存のUCメカニズムは,しばしば金属イオン間の直接のエネルギー転送に基づいているため,材料の設計と調節性を制限しています.
研究 の 目的:
- アセンブリ誘発興奮マルチメアの状態を利用して新しいランタニド有機複合体を合成する.
- 調整可能なUC材料の設計のための新しい戦略を実証する.
主な方法:
- 2種類のLn8L12型ランタニド-有機複合体の合成
- 980 nm刺激下での上向き変換された光の特徴化.
- 協調的な感受性および興奮-マルチメディアドエネルギーリレーメカニズムの研究
主要な成果:
- Yb8 ((L2R/S) 12) アセンシビライゼーションによる多重緑色光が示された.
- ヘテロメタリック (Yb/Eu) 8L12アセンブリは,エキサイテッド-マルチメーター媒介のエネルギーリレーを通して,上向きに変換された赤色の放射を達成した.
結論:
- アセンブリ誘発のエキサイテッドマルチマー状態はUC材料設計の新たな経路を提供します.
- このアプローチは,高度な光機能のための多成分ランタニド-有機複合体の設計性と調整性を高めます.