偶氮三唑為橋基之多核鐵簇錯合物合成.結構與磁性研究

Synthesis, Structure and Magnetic Characterization of dmatrz (3,5-dimethyl-4-amino-1,2,4-triazole)-base polynuclear iron complexes

林欣怡(Hsin-Yi Lin)

指導教授 ： 王瑜

國立臺灣大學/理學院/化學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.02703

摘要

具有多核性與恰當的拓樸學之特質的多核金屬簇，由於本身在基態時擁有大規模的整體自旋數值，因此有時能夠作為單分子磁鐵(single-molecule magnets , SMMs)的應用潛力。目前的研究主要是著重在以氧原子和含氮的triazole配基作為架橋配基，進一步地設計及合成出多核鐵金屬簇(polynuclear iron clusters)。 成功地合成出三個新穎多核鐵簇化合物︰
(一) [Fe4(μ4-O)(μ-OR)4(μ-dmatrz)3(NCS)6] ,
(μ-OR = CH3CH2O(1) ; CH3O (2))
(二) [Fe3(μ-dmatrz)4(O)(OH)(NCS)6].2H2O (3)

在第一系列鐵簇錯合物[Fe4(μ4-O)(μ-OR)4(μ-dmatrz)3(NCS)6] , (μ-OR= CH3CH2O (1) ; CH3O (2))中，這兩個鐵簇都具有相同的晶體結構(isostructure)，都是由一個氧原子連接著四個金屬鐵離子為一[Fe4O]結構單元形成四角錐狀(tetrahedral)之四核鐵簇。錯合物(1)和(2)之平均鐵金屬離子與氧之間鍵長分別為2.019(2)、2.017(2) Å；平均鐵金屬離子與氮之間鍵長分別為2.185(4)、2.194(4) Å。第二系列的錯合物(3)為一個直線形的三核鐵金屬簇，其位於中間處的鐵離子位於反轉中心上，並經由四個triazole配基以N1,N2架橋鍵結模式和兩個氧橋來連接著兩個末端的鐵離子而構築成扭曲的八面體結構(distortion octahedral)，其中間的鐵離子與氮跟氧原子之間平均鍵長分別2.155(3) 和1.896 (2) Å。除了架橋配基之外，位於末端處的鐵離子也由另外三個NCS陰離子所提供的氮原子以fac 形態鍵結而形成六配位的配位環境。
本研究中將經由電化學之循環伏安法(CV) 量測來研究其電化學性質、電子順磁共振光譜(EPR)來鑑定推斷出鐵離子所具有未成對的電子數目、X光吸收光譜(K-edge and L-edge)來決定多核鐵離子的氧化態和自旋態，並經由超導量子干涉儀的測量來探討多核鐵金屬簇的磁性現象，皆顯示鐵簇錯合物(1)、(2)和(3)都為強烈的反鐵磁作用力之磁性性質，並利用鐵之K-edge 和L-edge X光吸收光譜分析來決定多核鐵離子的氧化態和自旋態，也能進一步地去了解作為架橋配基的氧原子應為hydroxide (OH-)或是oxide (O2-)。

關鍵字

多核鐵簇 ； 磁性 ； X光吸收光譜

並列摘要

Abstract

Metal cluster assembly with high nuclearty and appropriate topology could sometimes have a large total spin values (S) at ground state that can function as a single-molecule magnet (SMM). The present research is focusing on the design and synthesis of polynuclear iron clusters with primarily oxygen, triazole ligands as bridging ligands.
Three novel cluster compounds [Fe4(μ4-O)(μ-CH3CH2O)4(μ-dmatrz)3(NCS)6] (1), [Fe4(μ4-O)(μ-CH3O)4(μ-dmatrz)3(NCS)6] (2) and [Fe3(μ-dmatrz)4(O)(OH)(NCS)6].2H2O (3) have been synthesized and structure characterized. Complex 1 and 2 are isostructure with the cluster consists of Fe4O unit and an O atom connects to four iron atoms to form a trigonal pyramid with the average Fe-Oavg (oxo) =2.019(2) and 2.017(2); Fe-Navg(μ-dmatrz)= 2.185(4) and 2.194(4) Å for 1 and 2, respectively. Complex 3 consists of linear trinuclear iron cluster. The central iron of the cluster is located at a crystallographic inversion center and connected to two terminal iron atoms through N1,N2-bridging mode of four triazole ligands and two oxygen bridging to adopt a distorted octahedral conformation (Fe-Navg(μ-dmatrz) = 2.155 (3) and Fe-O = 1.896 (2) Å). In addition to the bridging ligands, the six-coordinated environment of the terminal iron is completed by nitrogen atoms of three NCS- anions in a fac configuration.
The magnetic properties, studied by SQUID magnetometer, reveal strong antiferromagnetic interaction between the iron centers of complex 1, 2 and 3. The Fe K- and L-edge X-ray absorption spectroscopy (XAS), EPR and CV measurements are resolved the oxidation and spin state of the iron, as well as to determine the bridging oxygen atom being hydroxide or oxide.

並列關鍵字

polynuclear iron clusters ； magnetic property ； XAS

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