場所によって差異化され,高スピン鉄のクラスターにおける一酸化炭素のレドックス依存結合のための熱力学モデル
Charles H Arnett1, Matthew J Chalkley1, Theodor Agapie1
1Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States.
Journal of the American Chemical Society
|March 29, 2018
まとめ
レドックス化学は,低スピンの複合体とは異なり,COに対する高スピンの鉄のクラスタ afinity に最小限の影響を及ぼします. 電子移転はFe ((III)) 部位でのCO結合を促進し,窒素化コファクター結合のメカニズムを示唆する.
科学分野:
- バイオ有機化学
- 有機金属化学
- 生物化学
背景:
- 窒素酵素のFeMo共因子は,その酸化還元状態の影響でN2とCOを結合する.
- リドックス変化が π 酸に対する高スピン鉄のクラスタ afinity にどのように影響するかを理解することは極めて重要ですが,十分に解明されていません.
研究 の 目的:
- 場所によって区別された鉄のクラスターによる一酸化炭素 (CO) の結合親和性と活性化に対するリドックス化学の影響を調査する.
- 高スピン鉄のクラスターと低スピンと単金属鉄の複合体のリドックス効果を比較する.
主な方法:
- 場所によって区別された鉄のクラスターを合成し,可逆的なCO結合が可能である.
- Fe (II) 4からFe (II) Fe (III) 3までの酸化還元状態を検出するための電気化学的研究.
- CO結合と活性化を評価するために,光譜分析 (例えば, νCO 周波数).
主要な成果:
- 1電子リドックスイベントは,高スピン鉄のクラスターに対するCO親和性と活性化にわずかな変化 (最大400倍) を引き起こした.
- 対照的に,低スピンおよび単金属鉄複合体は,結合部位における酸化還元化学により,大きな親和度 (105−10^22倍) を示した.
- 遠隔の金属センターでの電子負荷は,CO結合エネルギー (~1 kcal·mol−1) を最小限に影響したが,内部電子移転を通じてFe (III) センターでのCO結合を可能にしました.
結論:
- レドックス化学は,高スピンの鉄のクラスターのCO結合親和性に限られた直接的な影響を及ぼします.
- クラスター内の遠隔電子転送は,小さなエネルギーペナルティでFe (III) センターでのCO結合を促進します.
- これらの発見は,FeMo-コファクターによるN2とCOの調整のメカニズムを示唆し,潜在的にコファクターの酸化エッジを含む.
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