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Atomic Layer Deposition of Vanadium Dioxide and a Temperature-dependent Optical Model
Published on: May 23, 2018
マンガン ((V) -オクソポリオクソメタラート中間物の特徴と,酸素移転反応におけるそれらの性質
Alex M Khenkin1, Devesh Kumar, Sason Shaik
1Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel 76100.
Journal of the American Chemical Society
|November 30, 2006
まとめ
この研究では,酸化触媒として,マンガン代用ポリオキシメタラート (P2W17MnIII) を調査しています. 高反応性の理論的予測にもかかわらず,実験結果は,ポリオキソメタラートの電荷とエントロピーに対する溶媒効果のために,より遅い触媒を示しています.
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
- 材料科学 材料科学とは
背景:
- ポリオキソメタラート (POM) は,調節可能な性質を持つ多用途の無機クラスターです.
- マンガン代用POMは酸化触媒として有望であることが示されています.
- 活性部位の電子構造と反応性を理解することは,触媒設計において極めて重要です.
研究 の 目的:
- マンガン (III) に置換されたポリオキシメタラート,P2W17MnIIIの触媒活性を調べるために,モノ酸素ドナーとしてイオドペンタフローロベンゼンビス (F5PhI (TFAc)) (F5PhI (TFAc)) を用いた.
- カタリシス中に形成されるマンガン-オクソ種の電子構造と反応機構を解明する.
- 実験的反応性を理論的予測と比較し,触媒性能を制限する要因を特定する.
主な方法:
- 反応中介物質と種を特定するために,光譜的特徴付け (19F NMR, 31P NMR) を行う.
- 電子構造と移行状態をモデル化するための密度関数理論 (DFT) 計算.
- 反応速度と活性化パラメータを決定するために,基板として1オクテンを用いた運動測定.
主要な成果:
- マンガン ((V) -オクソ種 (P2W17MnV=O) の形成が観察されました.
- DFTの計算は,エポキシデーションとヒドロキシル化の低層のトリプルトランジション状態を予測し,高い反応性を示唆しました.
- 実験的な動力学は,予想より低い反応性を明らかにし,これは活性化の非常に負のエントロピーに起因する.
結論:
- P2W17MnIIIのマンガン ((V) -オクソ種は,類似のポーフィリン複合体よりも反応性が低い.
- 極性溶媒と水による高電荷のポリオックスメタラートの強い溶解は,移行状態に大きな影響を及ぼします.
- 溶媒分子の電圧と自由度損失は,活性化の負のエントロピーをもたらし,触媒効率を低下させます.
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