含鎳超氧化物歧化酶活性中心之擬態化合物研究―具軸位吡啶配位之含氮硫五牙基二價鎳錯合物之合成、結構及反應性之探討

Sythesis, Structure and Reactivity of N3S2-NiII Complexes Containing Axial Pyridine Relevant to the Active Site of Nickel Superoxide Dismutase (Ni-SOD)

朱允立

指導教授 ： 李位仁

國立臺灣師範大學/理學院/化學系/碩士(2011年)

摘要

為了模擬含鎳過氧化物歧化酶 ( Ni-SOD)，我們利用兩個立障大的含氮硫五牙配位基H2PPCMP以及H2IPCMP，合成四個鎳錯合物：[Ni(H2PPCMP)](ClO4)2 (1)、Ni(PPCMP) (2)、[Ni(H2IPCMP)](ClO4)2 (3)與Ni(PPCMP) (4)，並利用X光繞射結構解析、紫外/可見光光譜、核磁共振光譜以及循環伏安法，針對這類少見又具有吡咯啶/硫代酰胺、軸配位吡啶的鎳錯合物，展現此四個錯合物的特徵。
錯合物2和4是由錯合物1和3經過去質子化所得到，並預期它們會形成正三價鎳錯合物。然而，錯合物2和4在電化學探討出現不可逆的氧化還原行為，意指此二錯合物無法形成穩定的正三價鎳錯合物。
雖然 鎳錯合物 1 與 3 的差別僅在於前者配位基是拉電子基而後者是推電子基，但他們在化學性質上相當不同。其錯合物特徵吸收峰的波長大小可反映配位基的給電子能力。於紫外光/可見光光譜中，以二氯甲烷作溶劑的時候，錯合物 1 特徵吸收峰的波長出現於353 nm，而錯合物 3 在於362 nm 。循環伏安法中以Fc/Fc+ 做為參考電位時，可發現錯合物 3 於0.836V處具有一個ΔEp為87 mV的可逆NiIII/NiII氧化還原峰，而錯合物 1僅具有擬可逆NiIII/NiII氧化還原峰。此現象可能因為錯合物 3的配位基上具有推電子取代基，因此thioamide上的N-H鍵較強，因此在中心鎳離子氧化成正三價時，不易進行去質子反應變成其他物種而分解，所以在循環伏安圖譜中具有可逆的NiIII/NiII氧化還原峰。此結果說明H2IPCMP配位基有機會穩定正三價鎳錯合物。

關鍵字

含鎳超氧化物歧化酶 ； 軸位吡啶 ； 含氮硫五牙基

並列摘要

In order to mimic the Ni-SOD, four nickel complexes, [Ni(H2PPCM P)](ClO4)2 (1), Ni(PPCMP) (2), [Ni(H2IPCMP)](ClO4)2 (3), and Ni(IPC MP) (4), with a bulky ligand , H2PPCMP or H2IPCMP were synthesized and characterized by X-ray diffraction, UV/vis, and 1H-NMR spec- troscopies, and cyclic voltammetry. Such five-coordinate nickel comple- xes containing a mixed thioamide/pyrrolidine ligand were rare in literature.
Complexes 2 and 4 were the deprotonated products of complex 1 and 3, respectively, and expected to form Ni(III) complexes. However, the irreversible redox behavier was observed for complexes 2 and 4 suggestind that both complexes could not form the stable Ni(III) complexes.
Complexes 1 and 3 are only varied by an electron-accepting to an electron-donating ligand, but their chemical properties are quite different. The λmax appears to reflect the donating strength of the ligand. The λmax of 3 is at 362 nm while that of 1 occurs at 353 nm in CH2Cl2. A reversible NiIII/NiII redox couple was observed for complex 3 at 0.836V versus Fc/Fc+ with a ΔEp of 87 mV; whereas, a quasi-reversible NiIII/NiII redox couple was observed for complex 1. This can be easily explained by the fact that the stronger N-H bond of thioamide of 3 results a considerably more reversible oxidation potential and no decomposition was occurred through oxidation process. This result implies that the electron-donaing H2PPCMP better stabilizes the Ni(III) complex after oxidation.

參考文獻

18. Huaibo Ma; Swarup Chattopadhyay; Jeffrey L. Petersen; Michael P. Jensen. Inorg. Chem. 2008, 47, 7966-7968.

12. Adam T. Fiedler; Peter A. Bryngelson; Michael J. Maroney; Thomas C. Brunold. J. Am. Chem. Soc. 2005, 127, 5449-5462.

7. Anne-Frances Miller. Acc. Chem. Res. 2008, 41,501-510

9. Timothy A. Jackson; Thomas C. Brunold. Acc. Chem. Res. 2004, 37, 461-470.

19. Marcello Gennari; Maylis Orio; Jacques P_ecaut; Frank Neese; Marie-Noelle Collomb; Carole Duboc. Inorg. Chem. 2010, 49, 6399- 6401