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| 研究生： |
姜博仁 |
|---|---|
| 論文名稱： |
微粒體甲烷單氧化酵素之結構與功能性之模型三核銅金屬簇化物之研究(II) Structural and Functional Models for the Trinuclear Copper Clusters of the Particulate Methane Monooxygenase(II) |
| 指導教授： | 陳炳宇 |
| 學位類別： |
碩士 Master |
| 系所名稱： |
化學系 Department of Chemistry |
| 論文出版年： | 2011 |
| 畢業學年度： | 99 |
| 語文別： | 中文 |
| 論文頁數： | 82 |
| 中文關鍵詞： | 微粒體甲烷單氧化酵素 、三核銅簇金屬化合物 、催化 |
| 英文關鍵詞： | Particulate methane monooxygenases, Trinuclear copper clusters, catalysis |
| 論文種類： | 學術論文 |
| 相關次數： | 點閱：116 下載：9 |
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三核銅簇錯化物在進行羥化反應時，是經由單氧直接嵌入的過渡狀態的一步反應機構。而在反應中經由三核銅簇錯化合物的自旋態調控，使其中之一的氧原子被活化至1D狀態，而頂端第三個銅離子的存在，能有效降低反應時“oxo-transfer”的活化能。
在我的第一個研究中，為了瞭解三核銅簇系統中頂端銅離子的角色，修飾7-Me與7-Et系統的配位基，改變其七環頂端的官能基成-OH基，分別得到兩個全新的7-OH-Me與7-OH-Et的配位基，藉由改變第三個銅離子的配位環境，希望探討三核銅簇錯化物的反應活性。我們首先使用氧氣來氧化以7-OH-Me為配位基所得到的三核銅一價簇錯化物[CuICuICuI(7-OH-Me)](X) (X=BF4,ClO 4)，結果使用不同陰離子氧化後的三核銅簇錯化物[CuIICuII (-O)CuII(7-OHMe)](X) (X=BF4,ClO 4)，根據ESI-MS光譜 ，其主訊號分子量的差等於個別所含一個陰離子的分子量差異，推測其七環頂端的O-H基的氧配位在第三個銅離子上。此外，ESI-MS存在一組與主訊號峰相差m/z =14 amu的訊號，推測可能是氧化反應時，分子內反應，而使一個甲基脫掉所得。
接著我們分別使用氧氣、TBHP以及H2O2來氧化以7-OH-Et為配位基所得到的三核銅一價簇錯化物[CuICuICuI(7-OH-Et)](X) (X=BF4,ClO4)，根據ESI-MS光譜，其主訊號峰均是 {[CuIICuII (-O)CuII(7-OH-Me)](X) (X=BF4,ClO 4) + m/z = 57 amu}的訊號，推測其可能是溶劑CH3CN氧化所造成。使用CD3CN代替溶劑，卻發現主訊號峰與原來相同，並未偏移 m/z =3 amu。推測可能跟原本使用銅離子來源[CuI(CH3CN)4](BF4)的配位溶劑相關。這系列7-OH-Me與7-OH-Et的兩個系統，使用200當量H2O2當作氧化劑，對環己烷進行氧化催化反應，得到的轉化率與TON並不佳。
在第二個研究中，根據本實驗室先前發展的[CuICuICuI(7-Dipy)] (X=BF4,ClO 4)系統，使用H2O2當作氧化劑，對環己烷進行氧化催化反應。對其七環頭上做-OH的官能基改變，根據氧化後的ESI-MS光譜，經由使用不同的陰離子(BF4 or ClO4)，證實氧化後可得[CuIICuII (-O)CuII(7-OH-Dipy)](X) (X = BF4,ClO 4)，推測七環上-OH基的氧原子並未配位在上方頂端銅離子上，使用200當量H2O2當作氧化劑，對環己烷進行氧化催化反應，得到的轉化率與TON與[CuICuICuI(7-Dipy)]+系統類似。利用此一特性，改變官能基-OH成-SH，利用-SH官能基可接在金薄膜電極表面上的特性，未來我們將進行一系列電催化反應。目前，在合成-SH鍵的配位基上，還未達到有較好產率的合成設計，必須進一步改良合成的步驟，來達到較高純度的產物。
It is known that the hydroxylation of alkane molecules catalyzed by trinuclear copper complexes through the “oxene” insertion mechanism. The active “oxene” with a “1D” spin state will have lower reaction energy barrier when it is tuned by three copper ions.
In my first study, for understanding the role of the copper ion in the apex position in the scaffold of isosceles tricopper cluster, we modified a hydroxyl group on the 7-membered amino ring to obtain two whole new 7-OH-Me and 7-OH-Et ligands. By means of the modified hydroxyl group, it is capable of mediating the electron densities on the vertex of copper triad. According to the ESI-MS spectra of oxygenated [CuICuICuI(7-OH-Me)] and [CuICuICuI(7-OH-Et)], which are synthesized by mixing one equiv. of ligand and three equiv. of [CuI(CH3CN)4](BF4 or ClO4), the cluster signals which are associated with [CuIICuII(-O)CuII(L)](X) (L = 7-OH-Me or 7-OH-Et; X = BF4 or ClO4) only appear. Interestingly, a minor signal with m/z = 14 molecular weight lower than [CuIICuII(-O)CuII(7-OH-Me)](X) are suspected to encounter N-demethylation, and the main signal of oxygenated [CuICuICuI(7-OH-Me)] present a [CuIICuII(-O)CuII(7-OH-Me)](X) tricopper complex plus a m/z = 34 amu. However, the main signal of oxygenated [CuICuICuI(7-OH-Et)] refers to a [CuIICuII(-O)CuII(7-OH-Me)](X) tricopper complex plus a m/z = 57 amu. These two ESI-MS spectra are not seen in the corresponding oxygenated [CuICuICuI(7-Me)]+ and [CuICuICuI(7- Et)]+.
In my second study, based on our previous studies about efficient oxidation of cyclohexane catalyzed by [CuICuICuI(7-Dipy)]+ in the bulk of H2O2, we modified the ligand 7-Dipy to a 7-OH-Dipy as well. However, the ESI-MS of oxygenated [CuICuICuI(7-OH-Dipy)] present a main cluster, [CuIICuII(-O)CuII(7-OH-Dipy)](BF4 or ClO4)2, which shows the modified hydroxyl group is not linked to the copper ion completely different from the 7-OH-Me and 7-OH-Et ligands. Nevertheless, the hydroxyl group on the 7-membered ring might be replaced by a thiol group (-SH) to anchor the active [CuICuICuI(7-Dipy)]+ tricopper on the gold thin film for a series of electrochemical studies.
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