Sm(II) - プロトン結合電子移転:非常に弱いN-HとO-Hの同解結合強度とそれらを制御する要因の定量化
Emily A Boyd1, Jonas C Peters1
1Division of Chemistry and Chemical Engineering, California Institute of Technology (Caltech), Pasadena, California 91125, United States.
Journal of the American Chemical Society
|November 8, 2022
まとめ
この研究では,強力な陽子結合電子伝送 (PCET) 反応剤として作用する,明確に定義されたサマリウム (II) 複合体を導入し,特殊な弱いN-HとO-H結合の精密な測定を可能にします.
科学分野:
- 有機金属化学
- レドックス化学
背景:
- サマリウム二酸化物 (SmI2) は,陽子結合電子移転 (PCET) 反応で使用される単電子還元剤である.
- SmI2の反応性は,テトラヒドロフラン (THF) /アルコールなどの一般的な溶媒の混合物における定義が不十分であるため,制限されている.
- 結合解離自由エネルギー (BDFE) のような正確な熱力学データは,Sm媒介のPCET反応性を理解し,予測するために重要である.
研究 の 目的:
- SmIIベースのPCETの反応性を研究するための明確に定義されたモデルシステムを開発する.
- 機能化されたマクロサイクリックリガンドを持つ複合体におけるN-HとO-H結合のBDFE値を正確に決定する.
- このモデルシステムの反応性を従来の SmI2/THF システムと比較する.
主な方法:
- 溶解性を確保し,二分化を防ぐために,大容量でケラートするマクロサイクルリガンド ((ArOH) 2Me2cyclam) の合成.
- マクロサイクルリガンドによるSmII複合体の電気化学的特徴化.
- 2-ピロリドンとMeOH複合体のBDFEsを計算するための熱力学パラメータの直接測定
- 結合の弱まりの原因を解明するために,拡張された熱化学サイクルを分析する.
主要な成果:
- ((ArOH) 2Me2cyclam) SmII複合体は,クリーンな電気化学的行動を示し,溶解性を維持する.
- 2- ピロリドン (< 27. 2 kcal mol - 1) とMeOH (< 24. 1 kcal mol - 1) 複合体に対して,例外的に弱いN- HとO- HBDFEを測定した.
- 結合の弱化は,強く還元するSmII中心と強いSmIII-ピロリドナート/アルコキシード相互作用に起因する.
結論:
- 開発されたモデルシステムは,SmIIベースのPCETのための信頼性の高い熱力学データを提供します.
- 取得したBDFE値は,THFにおけるSmI2で通常観測される値より著しく低い.
- この作業は,SmIIベースの効率的な (電気) 触媒システムの設計のための道を開く.
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