直線型混價鎳金屬串與不對稱多核混金屬串之系列錯合物之合成與性質研究

Synthesis and Studies of a Series of Linear Mixed-valence Nickel-based and Asymmetric Hetero-polynuclear Metal String Complexes

華紹安(Shao-An Hua)

指導教授 ： 彭旭明

國立臺灣大學/理學院/化學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.01881

摘要

近年來，金屬串分子因具有成為未來分子器件的潛力而有著顯著的研究。在本研究中，我們致力於發展新型的金屬串分子。其中包含了兩個系列，分別為具有混價單元的鎳金屬串分子及多核混金屬串分子。
第一部分的研究為混價鎳金屬串分子的合成與性質研究。首先是一系列對稱型的七核及九核鎳金屬串。這些分子的末端都帶有可氧化還原的雙核混價鎳金屬單元。利用這樣的特性，透過磁性、電化學實驗的分析和比較，可了解電子在雙核混價鎳金屬單元之間的作用力與分子長度之間的關係。此外，我們也設計了另一種不對稱型的配基架構，利用配位環境上的差異達到調控不對稱型七核鎳金屬串的電子結構。藉由此設計的概念，此分子是第一個同時具有三種不同氧化態的鎳金屬所形成的混價金屬串分子。我們對此化合物也進行了多種光譜及理論計算的分析。
在研究的第二部份，我們採用了傳統的三吡啶二胺配基與雙核的釕、錸金屬與鈷、鎳金屬形成異核的金屬串分子。實驗上採用了管柱層析的方法純化以得到目標產物。同時也透過NMR、IR、電化學、X-Ray 等技術對此類分子做純度及結構上的鑑定與分析。實驗結果與之前建立的三核釕鎳(釕鈷)混金屬做比較分析，其五核釕鎳(釕鈷)異核金屬串為混價的電子組態。我們也對此類分子做了單子的導電度量測與分析。結果顯示，在金屬串分子裡引入具有較強的金屬金屬作用力的雙
核釕單元可有效提升分子的導電度，故此設計概念為一有效改良導電度的方法。
最後，在合成錸鎳混金屬串的實驗中，我們得到了不對稱型的四核錸鎳混金屬分子。由於配基具有不對稱但規則的排列方向，此分子並沒有晶體失序的表現。其末端未配位的吡啶單元，提供了進一步配位金屬的能力，使此分子具有混合三種不同金屬的金屬串分子之潛力。

關鍵字

金屬串 ； 導電度 ； 金屬線 ； 奈米導線 ； 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 future nano-electronics. In order to develop new generation of metal string complexes, two series of them, which contain a mixed-valence polynickel backbone or a heterometallic framework, have been studied.
The first study concerns two kinds of mixed-valence polynickel metal strings. The first kind is a symmetrical type nickel string, which includes [Ni7(bnapy)4Cl2](Cl)2 (3), [Ni9(bnapya)4Cl2](PF6)2 (4), [Ni7(bnapy)4Cl2](PF6)4 (5) and [Ni9(bnapya)4Cl2](PF6)4 (6) (bnapy2– = 2,6-bis(1,8-naphthyridylamido)pyridine and bnapya3– = bis(6-(1,8-naphthyridyl-
amido)pyridyl)amido). The extended nickel string complexes 3 and 4 possess two redox-active [Ni2(napy)4]3+ units. The electronic communication between the two redox-active units in both complexes can be investigated not only by magnetic measurements but also by analyzing the difference between two consecutive one-electron oxidation peaks (∆E1/2) of 3 and 4. The antiferromagnetic coupling between the two [Ni2(napy)4]3+ fragments becomes weaker as the metal frameworks elongated (J = –13.21 and –1.48 cm-1 for 3 and 4, respectively). Moreover, the ∆E1/2 values of 3 and 4 are 110 and 84 mV, respectively, which are smaller than that (300 mV) of their pentanickel analogue [Ni5(bna)4(Cl)2](PF6)2 (bna– = bisnaphthyridylamido) (1). These ∆E1/2 values indicate that the electronic communication decreases with increasing the number of inner diamagnetic nickel ions in nickel string complexes. The second type is an asymmetrical type of metal strings. The (4,0)- [Ni7(phdptrany)4Cl](PF6) (phdptrany3– = 2-(phenyldipyridyltriamido)-1,8-naphthyridine, 7) displays an intriguing electronic structure among the Ni-based metal string family. Because of the different coordination abilities on the terminal positions of phdptrany3–, complex 7 exhibits a charge disproportionate metal framework (Ni2)3+–NiII–NiII–(Ni3)7+ that contains two MV units with delocalized Ni–Ni bonds. This interesting character is first observed by analysis of Ni–Ni bond distances, which display remarkable contraction in comparison with other similar asymmetrical Ni-strings. Then, the antiferromagnetic interaction (J = –53.3 cm–1), as well as the absorption in the Near-IR region, indicative of the existence of two MV units within the metal framework. Furthermore, DFT calculations reveal that the relative lower energy of this charge disproportionational model compared to the charge localized model (0.63 eV).
In the second part, three asymmetrical heteronuclear compounds [NiRu2Ni2(tpda)4(NCS)2] (10), [Ru2Co3(tpda)4(NCS)2] (11) and [Re2Ni2(tpda)4(NCS)](PF6) (12) (tpda2–= tripyridyldiamido) are synthesized and characterized. By using techniques such as 1H NMR, IR, electrochemistry, UV/Vis/Near-IR and magnetism, the purity and the electronic structures are investigated. Complexes 10 and 11 can be regard as the extension of [RuRuM(dpa)4Cl2] type of heteronuclear metal strings. The combination of different metal ions within the metal framework provides the great potentials for the design the future electronic devices. Complex 12, on the contrary, displays an unambiguous structural character due to the asymmetrical arrangement of tpda2– ligand. It shows a very short Re–Re distance about 2.1695(4) Å. The electronic structure of 12 can be ascribed as a NiII–NiII–ReIII–ReIII chain. Interestingly, the non-coordinated pyridyl rings might be useful for the further coordination that results in the formation of MA–MA –MB–MB–MC type metal string complex.

並列關鍵字

Metal string ； Conductance ； Metal wire ； Nano-Wire ； Inorganic compound

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