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標題: | 內含雙核鉬單元金屬串及其長鏈配基之構型及電子結構研究 On the Electronic Structures and Conformations of Surrounding Ligands in Extended Metal Atom Chains Containing Dimolybdenum Subunits |
作者: | Tsai-Jung Liu 劉采容 |
指導教授: | 金必耀(Bih-Yaw Jin) |
關鍵字: | 金屬串分子,密度泛函理論,SSH 模型,配機構型,螺旋翻轉, Extended Metal Atom Chains (EMACs),DFT,Su-Schrieffer-Heeger model (SSH model),Ligand Conformation,Helical Perversion, |
出版年 : | 2018 |
學位: | 碩士 |
摘要: | 從奈米級的DNA結構到宏觀的植物卷鬚,自然界存在大量的螺旋構形。而同時包含左旋和右旋螺旋片段的的半螺旋構形(即手性逆轉,或稱為螺旋翻轉)也十分常見,並早在19世紀即在植物卷鬚上被特別研究過。最近,彭旭明和他的實驗團隊在一種特殊類型的分子¬──金屬串分子(EMACs)中發現了半螺旋構形的分子類似物。金屬串分子是一種由一系列金屬構成的中心長鏈和四個左旋或右旋螺旋結構的有機配基連接而成的多核錯合物家族。
在新合成的Mo2NiMo2(tdpa)4X2(X為軸向配基)分子中,顯現出了其配基螺旋性翻轉的可能。我們希望藉由這項工作,發掘此類分子構形的起源與條件,並通過密度泛函理論,證明螺旋配體的形成可歸因於中心金屬-金屬鍵和外圍碳-氮鍵鍵長的不匹配。實驗自三核金屬串(尤其是獨特的非螺旋npo配基金屬串)探討起,並闡述了金屬-金屬鍵長與氮-金屬-金屬-氮二面角之間的關係。此外,我們直接分析Mo2MMo2(tdpa)4(NCS)2 (M=Mn,Fe,Ni)系統以闡明其周圍配基的螺旋翻轉的來由,並說明隨著分子中心處的鉬-鎳鍵長增加,周圍配體中的半螺旋構形能量相對來說逐漸穩定。再者,我們也藉由推廣Su-Schrieffer-Heeger模型,建構與探討中心長鍊中原子的縱向排列與相連配基螺旋性質之間的關係。 Nature abounds with helical conformations in all scales ranging from nanoscale DNA structures to macroscopic tendrils in plants. The related hemihelical conformation that contains left-hand and right-hand helical segments simultaneously, i.e. the reversal of chirality – sometimes also referred to as a helical perversion, in the same chain, also occurs frequently and has been studied particularly in plant tendrils since the 19th century. The molecular analog of helical perversion has only been found recently by Peng and his coworkers in a special type of extended metal atom chains (EMACs), a family of multinuclear coordination complexes consisting of a string of metal atoms connected directly by metal-metal bonding and four surrounding organic ligands in left- or right-handed helical formations. The particular EMACs that show the possibility of helical perversions in its ligands have the general structural formula Mo2MMo2(tpda)4X2, where M=Ni, Co, … and X is the axial ligand. We hope to address the issue on the origin and conditions of their formations in this work. By using the DFT study, we demonstrate that the formation of helical ligands can be attributed to the unbalance of the bond lengths of central metal-metal bonds and peripheral carbon-nitrogen bonds. Starting from trinuclear EMACs, especially the unique nonhelical npo ligand EMACs, we illustrate the relationship between metal-metal bond length and the N-M-M-N dihedral angle, and the effect of ligand helicity on electronic structures. Furthermore, we analyze the Mo2MMo2(tpda)4(NCS)2 system directly to clarify the origin of its helical perversion on the surrounding ligands. Particularly, as the Mo-Ni bond length at the center is increased, the hemihelical conformation in the surrounding ligands is stabilized gradually. Furthermore, we built up a generalized Su-Schreiffer-Heeger model with linked springs representing the surrounding ligands in EMACs so demonstrate the coupling between the central chain longitudinal conformation and the ligand rotational conformation. |
URI: | http://tdr.lib.ntu.edu.tw/handle/123456789/1193 |
DOI: | 10.6342/NTU201801471 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 化學系 |
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