超高速光学刺激は,電荷移転特性を有する超分子金属サイクルで発生する
Daniel C Flynn1, Guda Ramakrishna, Hai-Bo Yang
1Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
Journal of the American Chemical Society
|January 9, 2010
まとめ
プラチナ金属サイクルの超高速ダイナミクスは,構造が電荷移転と興奮状態の寿命にどのように影響するかを明らかにします. 進んだ材料設計のための幾何学と結合の違いが,光学特性に影響を及ぼします.
科学分野:
- オーガノメタリック化学
- マテリアルサイエンス 材料科学
- フォトフィジックスの光学
背景:
- 二次元金属サイクリングと三次元金属サイクリングは,光学,電子,エネルギーアプリケーションにおいて極めて重要です.
- 超高速ダイナミクスを理解することは,新しい機能的材料の開発の鍵です.
研究 の 目的:
- 2つの異なるプラチナを含む金属サイクルの超高速ダイナミクスを調査する.
- サンブ・チャージ・トランスファー・ダイナミクスとインターシステム・クロス・レート.
- 構造的な差異と光学的性質を相関させる.
主な方法:
- フェムト秒の光向上変換スペクトロスコピー
- 暫定吸収スペクトロスコピーは,一時的な吸収スペクトロスコピーを用います.
主要な成果:
- 超高速のシステム間交差と電荷移転プロセスは,長方形と三角形の金属サイクルの間で異なります.
- 長方形の金属サイクルは,リガンド間の弱い電子結合を示します.
- 三角形の金属サイクルは,結合されたリガンドと金属の中心との強い相互作用を示し,結合が増加したより長い一時的な寿命につながります.
結論:
- メタルサイクルの次元性と構造は,光学特性に大きく影響します.
- 発見は,非線形光学材料の設計を導くことができます.
- 電子アプリケーションのための新しい,寿命が長い興奮状態の材料の開発の可能性.
関連する概念動画
03:02Colors and Magnetism
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 eye.
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 eye.
01:26Photochemical 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
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
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.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:52Stereoisomerism
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...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...