不對稱對甲基吡啶噻唑胺配基之三核混鉬/鎳異金屬串錯合物之合成與研究

本篇論文研究在於使用4-甲基吡啶噻唑胺 (4-methylpyridyl-thiazolylamine, Hmpta) 配基來合成出直線型三核混鉬/鎳異金屬串錯合物，並透過固態單晶結構、磁性、循環伏安法和電子吸收光譜來探討其性質。將4-甲基吡啶噻唑胺配基依序和Mo2(OAc)4、Ni(OAc)2•4H2O進行分段式高溫萘燒實驗，使用NaNCS當作軸向配基來源，便可得到三核混鉬/鎳異金屬串錯合物(3,1)-form [Mo2Ni(mpta)4(NCS)2] (1)，再將錯合物1和氧化劑ferrocenium hexafluorophosphate (FcPF6) 反應，便可以得到氧化過後的(3,1)-form [Mo2Ni(mpta)4(NCS)1.49Cl0.51](PF6) (2)，在經過單晶繞射解析後發現，兩個錯合物在配基或金屬離子部分都沒有失序 (disorder) 的產生，且螺旋纏繞的四個脫氫配基 (mpta-) 均以全順向式之配位模式和鉬/鎳金屬離子進行鍵結，位於金屬串兩端點的鉬/鎳金屬離子皆為五配位形式；而中間的鉬金屬離子則為四配位形式。在錯合物1之中，兩個鉬金屬離子之間的距離為2.1018 (6) Å，推測兩者之間存在著四重鍵 (quadruple bond) 作用力。而在氧化後的錯合物2之中，鉬鉬間距則為稍稍延長的2.1494 (9) Å，由此可知氧化是發生在鉬雙核單元之中 (Mo24+ → Mo25+)，且鍵級 (bond order) 因氧化而從4下降到3.5。為確定錯合物的電子組態，使用超導量子干涉儀來進行磁性的量測，由結果發現錯合物1可能屬於順磁性 (paramagnetism) 物質，其在300 K 下的有效磁矩μeff = 2.85 B.M.，和只考慮電子自旋時的理論有效磁矩μeff = 2.83 B.M. (S = 1) 接近。由此看來鉬雙核單元的電子組態為逆磁的四重鍵 (S = 0)，鎳金屬離子為高自旋電子組態 (S = 1)，並和透過結構鍵長分析所得到的結果相符合。經由循環伏安法發現錯合物1在氧化區段電位為E1/2 = +0.35 V 時有一組可逆氧化還原對，而在還原區段則無明顯氧化還原訊號。由電子吸收光譜發現錯合物1相較於配基本身，除了消光係數上升之外，同時還產生訊號紅位移的現象，並額外產生和金屬有關的躍遷吸收訊號。

關鍵字

噻唑；異金屬串；鉬

並列摘要

In this research, we report the linear trinuclear Mo/Ni heterometallic string complexes with 4-methylpyridyl-thiazolylamine (Hmpta) ligand, and investigate the properties of them by X-ray diffraction, cyclic voltammetry and electron absorption spectroscopy. In order to synthesize the trinuclear Mo/Ni heterometallic string complex (3,1)-form [Mo2Ni(µ3-mpta)4(NCS)2] (1), the ligand Hmpta is used to react with Mo2(OAc)4 and Ni(OAc)2•4H2O in refluxing naphthalene. Then the complex 1 reacts with oxidizing agent ferrocenium hexafluorophosphate (FcPF6) to obtain (3,1)-form [Mo2Ni(µ3-mpta)4(NCS)1.49Cl0.51](PF6) (2). Fortunately, The results of X-ray diffraction show that both complexes are no disorder between 4-methylpyridyl ring and the thiazolyl ring, and metal ions. The metal ions in complexes are helically wrapped by four deprotonated ligand (mpta-), which are all in syn-syn form to coordinate with Mo or Ni ions. The molecular structures reveal that the terminal Mo/Ni ions are five-coordinated and the inner molybdenum ion is four-coordinated. The distance between two molybdenum ions in complex 1 is 2.1018 (6) Å which shows that complex 1 have quadruple bond between two Mo(II) ions, however, the distance in complex 2 is slightly lengthened to 2.1494 (9) Å that shows the oxidation happen in dimolybdenum unit (Mo24+ → Mo25+), and bond order reduce from 4 to 3.5. The magnetic measurements show that complex 1 is likely paramagnetic compound, and μeff = 2.85 B.M. at 300 K which indicates that complex 1 is likely in a spin state of S = 1. On the other hand, there is a diamagnetic quadruple bond (S = 0) in dimolybdenum unit, and the electron configuration of nickel ion is high spin state (S = 1). The results of magnetism is consistent with X-ray structural analysis. The cyclic voltammetry of complex 1 exhibits only one reversible oxidation at +0.35 V in oxidative region, and there is no significant signal in reductive region. The electronic absorption spectrum indicates that there are obviously different between ligand Hmpta and complex 1, not only the increase of extinction coefficient but also the red shift of the absorption. Additionally, there are some transition which is related to metal center appear in complex 1.

並列關鍵字

thiazole ； heterometallic string ； molybdenum

參考文獻

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不對稱對甲基吡啶噻唑胺配基之三核混鉬/鎳異金屬串錯合物之合成與研究

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