ペンタデント酸ポリピリジルアミンリガンドによるコバルト複合体の電子およびステリックチューニング
Ping Wang1, Guangchao Liang2, M Ramana Reddy1
1Department of Chemistry , The University of Memphis , Memphis , Tennessee 38152 , United States.
Journal of the American Chemical Society
|June 28, 2018
まとめ
コバルト触媒におけるピリジンとイソキノリンの交換は,水素進化反応 (HER) の活性を著しく高めます. この構造的変更により,過剰な潜在力が低下し,H2生成の触媒効率が向上し,触媒設計に関する洞察が得られます.
科学分野:
- 協調化学
- カタリシス
- 電気化学
- 写真化学
- 水素進化反応 (HER)
背景:
- 分子コバルト触媒は,水素進化反応 (HER) の構造-機能関係を理解するために重要である.
- 以前の研究では,リガンド構造を改変することで,H2生成のための触媒性能を調整することが示されました.
- HER触媒におけるペンタデント酸コバルト複合体の軸性群の役割については,さらなる調査が必要である.
研究 の 目的:
- ペンタデント酸コバルト複合体の軸性イソキノリン群がHERに及ぼす電子およびステリック効果を調査する.
- 2つの新しいコバルト複合体を合成し,改造されたリガンド:DPA-1-MPIとDPA-3-MPIを特徴付ける.
- 水素生産のためのこれらの複合体の電気および光化学的性質を評価する.
主な方法:
- 2つの新しいペンタデント酸コバルト複合体の合成と特徴付け,Co ((DPA-1-MPI) ((H2O) ((PF6) 3とCo ((DPA-3-MPI)) ((H2O)) ((PF6) 3である.
- レドックスポテンシャル (CoII/CoIとCoIII-H/CoII-Hカップル) を決定する電気化学測定
- 水溶液での光触媒による水素生成実験
- 反応機構とエネルギーの解明のための密度関数理論 (DFT) の計算.
主要な成果:
- イソキノリンリガンドを含むコバルト複合体は,ピリジン類に比べて,電気化学的性質が著しく変化した.
- [Co ((DPA-1-MPI)) ((H2O)) ] ((PF6) 3は,リドックスポテンシャルで正のシフトを示し,[Co ((DPA-3-MPI)) ((H2O)) ] ((PF6) 3) よりも約32倍の活性で光触媒的なH2生成でした.
- DFT計算は,CoIからCoIII-HへのプロトネーションがDPA-1-MPI複合体にとってエネルギー的により有利であることを示し,低値コバルト種を安定させ,プロトン結合を促進する鍵として平面結合ビピリジル単位と電子ドナー軸性群を特定した.
結論:
- イソキノリン群を組み込むことにより,ペンタデント酸リガンドの構造的改変は,HERに対するコバルト複合体の触媒活性と電気化学的特性に大きな影響を及ぼします.
- 軸性リガンドの電子およびステリック性質は,重要な中間物質を安定させ,触媒サイクルにおける陽子転送ステップを容易にするために重要な役割を果たします.
- この研究は,効率的な分子水素生成触媒の開発におけるリガンド設計の重要性を強調する,誘導性H2進化のための改変された電子伝送-陽子伝送-電子伝送-陽子伝送 (mod-ECEC) 経路を提案している.
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