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標題: | 修飾三吡啶二胺配基(H2dpqda)及其直線型鎳金屬串錯合物之合成與研究 Syntheses and Studies of Modified Tripyridyl Diamine Ligand (H2dpqda) and the Linear Nickel String Complexes |
作者: | Chun-Chieh Chiu 邱俊傑 |
指導教授: | 彭旭明 |
關鍵字: | 金屬串,分子導線, metal string,metal-metal bonding, |
出版年 : | 2007 |
學位: | 碩士 |
摘要: | 本論文研究內容為吡啶奎林胺(Hdpq)之增長與三吡啶二胺(H2tpda)之微調的不對稱配基H2dpqda (2-dipyridyl-2’-quionlinyl diamine)與其直線型鎳金屬串錯合物合成、結構分析及磁性之探討。因為配基的不對稱,金屬串可能有四種構型的異構物,即(4,0)、(3,1)、(2,2) cis及(2,2) trans等構型。
將H2dpqda配基與Ni(OAc)2•4H2O高溫萘燒,加入NaSCN當作軸向配基之來源。由快速原子撞擊質譜(FAB-MS)可知有兩組訊號的產生,一是(4,0) form的[Ni5(μ5-dpqda)4(NCS)2],另一組訊號則是[Ni4(μ4-dpqda)3(μ3-Hdpqda)(NCS)],而可藉由晶體外觀明顯的不同來做分離。在H2dpqda配基與Ni(OAc)2•4H2O反應中加入LiCl,期望能藉由Cl-較大的立體效應控制金屬串的構型為(4,0) form。 由X-ray單晶繞射解析可知,(4,0)-[Ni5(μ5-dpqda)4(NCS)2]其立體效應大的奎林都在同一端,也因此造成結構上鍵長的變化。由於得到[Ni4(μ4-dpqda)3(μ3-Hdpqda)(NCS)]的單晶結構,推測微調後的H2dpqda配基也有類似三吡啶二胺的反應過程,而其單晶結構也受到奎林的影響產生改變。由(4,0)-[Ni4(μ4-Hdpqda)4(Cl)(F)](BF4)2的單晶結構,可知其構型為(4,0) form。磁性結果得知,(4,0)-[Ni5(μ5-dpqda)4(NCS)2]與(4,0)-[Ni4(μ4-Hdpqda)4(Cl)(F)](BF4)2的兩末端鎳離子皆為d8高自旋電子組態(S = 1)為反鐵磁性。[Ni4(μ4-dpqda)3(μ3-Hdpqda)(NCS)]因其特殊的部分非直線型結構與較遠的Ni(3)-Ni(4)距離,呈現弱的鐵磁性。 由單分子導電度量測可知,兩端鎳離子環境較不同的(4,0)-[Ni5(μ5-dpqda)4(NCS)2]並未呈現整流效果,其電阻值為27.5 MΩ與[Ni5(μ5-tpda)4(NCS)2]為24.0 MΩ差不多。期望之後能設計出新的不對稱配基,其金屬串將具有更好導電度與整流效果。 The aim of this thesis is to investigate the synthesis, structures, and correlative magnetic properties of linear nickel metal string complexes, where the new ligand is 2-dipyridyl-2’-quionlinyl diamine (H2dpqda). The design of H2dpqda ligand which exists sterical hindrance is expected to block the axial ligand. Due to asymmetrical H2dpqda ligand, nickel metal string complexes may have several isomers, e.g. (4,0), (3,1), (2,2) cis, (2,2) trans head-tail isomers. The H2dpqda ligand reacts with Ni(OAc)2•4H2O in high temperature of melt naphthalene, and the axial ligand is NCS- from NaSCN. From FAB-MS data, it shows two apparent signals. One is the five nickel metal string, [Ni5(μ5-dpqda)4(NCS)2] (1), and the other is [Ni4(μ4-dpqda)3(μ3-Hdpqda)(NCS)] (2). They can be separated by the different crystalline form. The reaction of LiCl with H2dpqda ligand and Ni(OAc)2•4H2O is expected to controll (4,0) form by using the chloride as axial ligand. Three linear nickel complexes 1, 2 and [Ni4(μ4-Hdpqda)4(Cl)(F)](BF4)2 (3) have been characterized by X-ray crystallography. The crystal structure shows that complex 1 belongs to (4,0) form and at crowded NCS axial ligand, the bond distances have many differences compared to [Ni5(tpda)4(NCS)2]. For complex 2, it is supposed to have the same reaction as H2tpda ligand. Complex 3 is also (4,0) form because of the chloride axial ligand. The magnetic results show complex 1 and 3 have two high spin nickel(II) atoms with antiferromagnetic coupling. The magnetic moment of complex 2 owning nonlinear crystal structure displays ferromagnetism. From STM data, unsymmetrical complex 1 does not show rectification. The resistance of a single complex 1 is 27.5 MΩ, not much different from that of complex 3 (24.0 MΩ). In the future, it is to expected to design new ligands to synthesize metal string complexes having better conductance and rectification. |
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