多吡啶胺配基之五核及七核異金屬錯合物之合成與研究

Syntheses and Studies of Penta- and Heptanuclear Heterometallic String Complexes with Oligo-α-pyridylamine Ligands

顏丞偉(Cheng-Wei Yan)

指導教授 ： 彭旭明

國立臺灣大學/理學院/化學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201900862

摘要

本實驗室主要致力於研究不同金屬搭配不同配基合成出具有導電性與金屬-金屬鍵的金屬串錯合物，並藉儀器去量測其導電度，再與其他金屬串分子做比較，希望在未來可以應用在電子元件上，發展為分子導線的奈米材料，對元件微小化是非常有幫助的。
本篇論文主要是利用傳統直線型配基Tripyridyldiamino ligand (H2tpda)與Tetrapyridyltriamindo ligand (H3teptra)混合不同金屬在高溫萘燒下進行反應，成功合成出最長七核異金屬錯合物[Ni2Ru2Ni3(μ7-teptra)4(NCS)2](PF6) (1)及不對稱混金屬錯合物[Os2Ni3(μ5-tpda)4Cl2](PF6) (2)、[Os2Co3(μ5-tpda)4Cl2](PF6) (3)。
由X-ray單晶繞射儀鑑定結構後發現，所有錯合物皆以四片全順向式配基螺旋纏繞在金屬離子外圍。對於1而言，中間失序的金屬為Ru雙核與Ni，雙核釕金屬單元為[Ru2]5+，其餘鎳金屬皆為正二價，磁性量測部分為在300 K時μeff為5.49 B.M.，推測金屬電子自旋依序為S = 1、0、3/2、0、1，接近純自旋理論μeff = 5.56 B.M.，合成此金屬串目的是想了解是否有負微分電阻的性質存在。錯合物1之單分子導電度8.53 × 10-4 G0 (電阻值為15.1 ± 4.8 MΩ)，與[Ni7(μ7-teptra)4(NCS)2] +之單分子導電度3.2 × 10-4 G0 (電阻值40.0 ± 7.9 MΩ)相比，導電度提高約兩倍左右; 另外，在I-V曲線圖中發現只有少部分的曲線才有NDR的現象存在。在電化學部分，有兩對可逆的氧化還原對E1/2 = 0.75 V和-0.16 V; 對2而言，金屬的部分沒有失序，Os-Os鍵長為2.3151(2) Å，為2.5個鍵序，於磁性量測部分為在300 K時μeff為4.95 B.M.，推測金屬電子自旋為S = 1、0、0、3/2，與純自旋理論μeff = 4.58 B.M.相近，為反鐵磁性。在3中，結構中的金屬有失序的情況，但鍵長仍落在合理範圍內，而磁性在300 K時μeff為3.05 B.M.，與純自旋理論μeff = 5.48 B.M.有落差，推估其未達飽和值的緣故，若溫度持續上升是有可能達飽和值的。

關鍵字

金屬串 ； 奈米導線 ； 單分子導電度 ； 無機化合物

並列摘要

Over the past few decades, a considerable number of studies have been made on metal string complexes which are believed to have the potential to be used for nano-electronics. Herein, we develop new generation of metal string complexes, which are the first example of the longest heteronuclear Ruthenium-based metal chain and Osmium-based metal string complexes.
The first part is to synthesize a novel heptanuclear heterometallic string complex [Ni2Ru2Ni3(μ7-teptra)4(NCS)2](PF6) (1), and the idea comes from pentanuclear metal string complex [Ni3Ru2(μ5-tpda)4(NCS)2], which showed some negative differential resistance (NDR) behavior. Thus, we try to synthesize and explore whether it still show the NDR behavior when prolonging the metal chain. For 1, the molecular structure reveals that the metal ions (NiII-NiII-NiII-Ru2V-NiII-NiII) are helically wrapped by four deprotonated teptra- ligands which adopted a syn-syn arrangement to coordinate with metal atoms. Furthermore, the central of three metal atoms (diruthenium unit and nickel atom) are disordered in the structure, resulting in the comparison of the bond length is unreliable in the central [Ru2Ni] unit. However, we still confirm that there exists a metal-metal bond (about 2.2498(3) Å) in diruthenium unit. The magnetic susceptibility measurement of 1 exhibits μeff = 5.49 B.M. at 300 K, which is consistent with the theoretical spin-only value μs.o. = 5.56 B.M.. Moreover, 1 also shows an antiferromagnetic interaction since the different electron spin coupling (S = 1、3/2 and 1). The conductance for single molecule of 1 is 8.53 × 10-4 G0, which is almost two-time higher than that of [Ni7(μ7-teptra)4(NCS)2]+ (3.2 × 10-4 G0), but 1 shows rarely NDR behavior around Ebias = 1.25 V in I-V curve diagrams. We consider that the main reason is due to the metal-metal bond in [Ru2] 5+ unit, which cause an increase of in electrical conductively. The results of cyclic voltammetry indicate the presence of two reversible redox couples at E1/2 = 0.75 V and -0.16 V.
In the second part, two asymmetrical pentanuclear heterometallic strings [Os2Ni3(μ5-tpda)4Cl2](PF6) (2) and [Os2Co3(μ5-tpda)4(Cl)2](PF6) (3) supported by H2tpda ligands are synthesized and characterized. By using X-ray single crystal diffraction, complex 2 shows that the structure is non-disordered, and Os–Os bond length is 2.3151(2) Å, but 3 have slightly disordered. The magnetic susceptibility measurements confirm that 2 and 3 exhibit an antiferromagnetic interaction since the different electron spin coupling (S = 1 and 3/2 for both 2 and 3). Furthermore, the effective moment μeff = 4.95 B.M. at 300 K for 2 is similar to the theoretical spin-only value μs.o. = 4.58 B.M. and μeff = 3.05 B.M. at 300 K for 3 is lower than the theoretical spin-only value μs.o. = 5.48 B.M., which is assigned to unsaturation magnetic moment. Cyclic voltammetry measurements of 2 shows two reversible redox couples at E1/2 = 0.37 V and -0.31 V; 3 reveals four reversible redox couples at E1/2 = 1.31 V、0.85 V、0.45 V and -0.30 V.

並列關鍵字

metal string ； nano-wire ； single-molecule conductance ； inorganic compound

參考文獻

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