鉻、鐵、鈷過渡金屬錯合物之電子組態與電荷密度研究

The investigation of the electronic configurations and charge density of Chromium, Iron and Cobalt transion metal

王澤元(Tze-Yuan Wang)

指導教授 ： 王瑜

國立臺灣大學/理學院/化學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.00803

摘要

複雜多變的分子系統的化學鍵與電子組態與化學反應息息相關。為了瞭解其中的物理化學細節，我們利用一系列的光譜方法來分析。同步輻射為近年來興起的非常重要的研究設施，本論文之實驗引用了多種不同能量吸收光譜，以及結合了不同的實驗方法如變形電子密度分析、電子密度拓樸學分析等，對於瞭解文中所述的三種錯合物系統的電子組態與化學鍵有很大的助益。第一章仿生錯合物鐵-一氧化氮[PPN][Fe(NO)(S2C6H4)2]系統以及其還原態分子的價數以及是否具non-innocent性質皆不容易確定。我們利用同步輻射X-ray吸收光譜術如金屬 K’L-edge , 與配基(N’S) K-edge來研究此系統。N K–edge吸收前緣為二重態分裂可以配合理論計算認定還原態分子的一氧化氮氧化態為NO·而(-1)價錯合物離子中之NO則為NO+氧化態。鐵金屬介於正一價至正二價之間。(-2)價錯合物離子未成對電子是分佈於鐵與一氧化氮之間，(-1)價錯合物離子未成對電子則是分佈在鐵與配基之間。另外從變溫實驗中也可以發現隨著溫度的降低，未成對電子未定域化區域可能會隨著改變。第二章[Co(bpy)3]2+錯合物為高自旋態離子錯合物。將此錯合物分子以ship-in-a-bottle的方式合成至Zeolite-Y的超孔洞中，因為受了沸石孔洞的侷限影響，會造成鈷錯合物[Co(bpy)3]2+從不具溫度驅動自旋交叉現象到具有溫度驅動自旋交叉現象。另一個例子為藉由金屬草酸架構來合成類似的化學計量定比系統。我們合成出錯合物[Co(bpy)3][LiCr(ox)3]也會因為侷限效應而造成自旋交叉現象。利用X-ray K-edge吸收光譜來研究其自旋相轉移的過程。根據理論計算得到的吸收邊緣光譜。發現Co K-edge在自旋交叉前後的吸收前緣變化主要是來自於結構的轉變(鍵長)，與Co本身之自旋態的關連性較小。最後一章我們展示了利用電子密度多極精算模型來研究錯合物[(C6H6)Cr(CO)3]的電子密度以及拓樸學分析。我們在苯環與金屬鉻之間找到了三個鍵臨界點，在CO與金屬鉻之間也找到三個。這代表此錯合物為一六配位形式。另外由Cr K-edge吸收前緣光譜確認鉻原子不具有中心對稱，與二苯鉻之光譜不同。

關鍵字

吸收光譜 ； 電子組態 ； 電荷密度 ； 仿生錯合物

並列摘要

The chemical bonds of a complicated molecular system are highly correlated to the electronic configuration and chemical reactions. In order to gain insight on the physical and chemical details of the molecular system, a series of spectroscopic techniques had been used. Synchrotron radiation becomes to be more and more important research facilities these years. In this thesis, the absorption spectra various energy are applied using this facility. Electron deformation density and topological properties are also applied to further our understanding of chemical bond. In the first chapter, the formal oxidation state and the non-innocent behavior of biomimic Iron nitrosyl complexes [PPN][Fe(NO)(S2C6H4)2] are still an open question. X-ray absorption techniques such as iron K’L-edge and Ligand(S’N) K-edge are used. The pre-edge feature are used to characterize the oxidation states of NO, it existed as NO· in the reduced (-2) complex anion, but as NO+ in the (-1) complex anion. The oxidation state of iron is between +1 and +2. The unpaired electron of (-2) complex anion is delocalized between Iron and nitrosyl group however the unpaired electron is delocalized between iron and thiolate ligand in (-1) complex anion. Such delocalization properties are changing with the change in temperature. In the chapter two, complex [Co(bpy)3]2+ is normally a high spin species, when loading these complex into the supercage of zeolite-Y, the thermally driven spin crossover occurred due to the confinement in the supercage of the zeolite-Y framework. A stoichiometric metal-oxalato compound [Co(bpy)3][LiCr(ox)3] is synthesized to confirm the spin crossover phenomenon using the Co K-edge absorption technique. The change in XANES region is mainly due to the difference in the Co-N bond length, little to do with spin state of Co. In the last chapter we demonstrate the chemical bonding with the deformation density and topological analysis of the complex [(C6H6)Cr(CO)3]. Three bond critical points are found between benzene ring and Cr atom and three bond critical points are located between Cr atom and carbonyl ligands. It represents the six-coordinated bonding character. The pre-edge region of Cr K-edge absorption demonstrates the site symmetry of the chromium atom is different from that of di-benzene chromium.

並列關鍵字

electronic configuration ； absoption specta ； biomimic complexes ； charge density

參考文獻

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