非ヘム・マンガン ((IV) -オクソ複合体の電子移転反応性が強化され,スカンジウムイオンと結合する
Heejung Yoon1, Yong-Min Lee, Xiujuan Wu
1Department of Material and Life Science, Graduate School of Engineering, ALCA, Japan Science and Technology Agency, Osaka University, Suita, Osaka 565-0871, Japan.
Journal of the American Chemical Society
|June 8, 2013
まとめ
スカンジウムイオン (Sc3+) は,マンガン-オクソ複合体の電子伝送率を大幅に高めます. この結合は反応機構を変化させ,酸化反応における触媒活性を高めます.
科学分野:
- 無機化学 無機化学とは
- カタリシス カタリシス カタリシス
- バイオ・オーガニック化学 バイオ・オーガニック化学
背景:
- ノンヘムマンガネス-オクソ複合体は酸化触媒において極めて重要です.
- 反応性に対する金属イオン結合の影響を理解することは,触媒設計の鍵です.
研究 の 目的:
- スカンジウムイオン (Sc3+) の結合がマンガン ((IV) -オクソ複合体の電子特性および反応性に及ぼす影響を調査する.
- 酸化反応における Sc3+ 調整によって引き起こされるメカニズム的変化を解明する.
主な方法:
- 複合体を特徴付けるために,光譜技術 (例えば,UV-Vis,EPR) が採用されました.
- 密度関数理論 (DFT) の計算を使用して,電子構造と結合相互作用を分析しました.
- 電子移転運動は,マルカス理論分析を用いて,様々な電子ドナーを用いて研究された.
主要な成果:
- スカンジウムイオン (Sc3+) は,マンガン ((IV) -オクソ複合体と強く結合し,Mn ((IV) ((O) - ((Sc3+) 1とMn ((IV) ((O) - ((Sc3+) 2) の種を形成する.
- Sc3+結合は,マンガン複合体の1電子還元ポテンシャルを大幅に増加させる.
- 2つのSc3+イオンの結合により,電子移転反応速度は最大107倍に増加し,これは低再構成エネルギーと高還元ポテンシャルに起因する.
結論:
- スカンジウムイオン協調は,マンガン ((IV) -オクソ複合体の電子移転反応性を劇的に高めます.
- Sc3+イオンの結合により,酸化硫化反応における反応機構は,直接の酸素原子移転から電子移転経路にシフトする.
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.
02:58Properties of Transition Metals
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
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...
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
01:21Radical Oxidation of Allylic and Benzylic Alcohols
Activated manganese(IV) oxide can selectively oxidize allylic and benzylic alcohols via a radical intermediate mechanism. Primary allylic alcohols are oxidized to aldehydes, while secondary allylic alcohols yield ketones. The redox reaction of potassium permanganate with an Mn(II) salt such as manganese sulfate (under either alkaline or acidic conditions), followed by thorough drying, yields the oxidizing agent: activated MnO2. While MnO2 is insoluble in the solvents used for the reaction, the...
01:19Complexation Equilibria: The Chelate Effect
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...