Ptナノ粒子の形状選択的エナチオ選択的水素化について
Erik Schmidt1, Angelo Vargas, Tamas Mallat
1Department of Chemistry and Applied Biosciences, ETH Zürich, HCI, CH-8093, Zürich, Switzerland.
Journal of the American Chemical Society
|August 1, 2009
まとめ
プラチナナノ粒子の形状は,エナチオセレクティブの水素化率と選択性に影響を与えます. プラチナ触媒の顔比が高くなると,触媒活性が強化され,キラル変形剤の吸収にエナティオメア過剰が加わります.
科学分野:
- 異質なカタリシスである.
- チラルの化学
- 表面科学とは,地表科学のことである.
背景:
- エナチオセレクティブ・ヒドロゲネーションは,キラル分子の合成に不可欠です.
- 金属ナノ粒子の形状が触媒性能に及ぼす影響は完全に理解されていません.
- チラルの変形剤は,水素化反応におけるエナチオセレクティビティを誘導するために不可欠である.
研究 の 目的:
- チラリックに改変されたプラチナ (Pt) ナノ粒子のエナチオセレクティブ水素化の構造感性を調査する.
- Ptナノ粒子の形状と表面面曝露 ({100} vs. {111}) が反応速度とエナチオセレクティビティに与える影響を決定する.
- 構造に依存した触媒的結果におけるキラル変形剤吸収の役割を明らかにする.
主な方法:
- 制御された形状 (立方体,立方体四面体,八面体) と平均サイズ10nmのPtナノ粒子の合成.
- チンコニジンとキニンをキラル変形剤として使用したエチルピルバートとケトパントラクトンのエナンチオセレクティブ水素化.
- Ptナノ粒子の形態学の関数として反応速度とエナティオメール過量 (ee) の分析.
- 密度関数理論 (DFT) の計算により,Pt(100) およびPt(111) 表面におけるシンコニジンの吸附行動が研究されました.
主要な成果:
- キラル変形剤がないため,Ptナノ粒子の形状は水素化の速度に影響を与えなかった.
- チンコニジンまたはキニンを加えることで,反応速度 (4-15倍) が著しく増加し,高いエナチオ選択性 (72-92% ee) が達成されました.
- Pt{111}対Pt{100}面の比率が高くなり,形状選択性を示す.
- DFTの研究では,Pt{111}と比較して,Pt{100}でシンチョニジンの強い吸収が示され,観察された構造の感受性を説明しました.
結論:
- Ptナノ粒子の形状は,キラル変形体が存在すると,エナチオセレクティブ水素化の決定的な影響を及ぼします.
- {111} 側面の比率が高い Pt ナノ粒子は,好ましいキラル変形剤吸収により,より活発で選択的です.
- Ptナノ粒子形態の最適化,特に{111}テラスを最大化することは,効率的で高度にエナチオセレクティブな水素化触媒の鍵です.
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