自旋轉換錯合物之的溶劑熱法合成與其光激發緩解現象的研究

Studies of spin-crossover complexes via solvo-thermal syntheses and their thermal relaxation of light excited kinetic phenomena

陳科華(KOWA CHEN)

指導教授 ： 王瑜

國立臺灣大學/理學院/化學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01726

摘要

藉由溶劑熱法我們成功了合成了cis-[Fe(tzpy)2(NCS)2] (1)分子，由室溫單經繞射的結果，我們可以得知其與自旋轉換起始物同時也是異構物trans-[Fe(tzpy)2(NCS)2](2)在空間上分子堆疊，與晶體中單一分子的鍵長鍵角的比較， cis-[Fe(tzpy)2(NCS)2]與trans-[Fe(tzpy)2(NCS)2]分子在室溫下具有相似的鐵氮鍵長，也都跟一般Fe(Ⅱ)高自旋態下的鐵氮鍵長相似。兩者也具有相仿的假想八面體[FeN6]中心，只是在配位NCS基有著鄰位與順位的空間上排列不同，在單位晶格空間上cis-[Fe(tzpy)2(NCS)2]是trans-[Fe(tzpy)2(NCS)2]分子的兩倍。
這是首次對自旋轉換於cis-trans異構分子間的物理化學性質的研究。只有些微不同的順反異構分子。順反異構的cis-分子中鐵具有相似的配位環境，對於自旋轉換性質影響極大的配位場強度也應該極為類似。由變溫磁性所得的測量結果我們可以知道cis-[Fe(tzpy)2(NCS)2]在可所量測的溫度範圍中(5-300 K)一直都維持在高自旋態，這跟我們原先所預期的結果完全不同，有趣的是如何從唯一的變因，也就是晶體堆疊上的不同來解釋這兩Fe(Ⅱ) 錯合物異構物分子，在磁性性質上的巨大差異。由實驗結果可以發現雖然只有些微不同的順反異構分子，即可造成分子堆疊的極大差異，進而影響了自旋轉換的發生與否，及迥然不同的 變化。此外這也是首次以液熱（solvothermal）合成方法轉換cis-trans異構金屬錯合物分子。也證明了以液熱方法是除了以氧化還原方法之外，提供了另一條途徑，合成一般化學方法難以合成的幾何異構物。

關鍵字

自旋轉換 ； 溶劑熱合成法 ； 亞鐵錯合物

並列摘要

The novel complex Cis-[Fe(tzpy)2(NCS)2](1) has been synthesized successfully from spin crossover trans-[Fe(tzpy)2(NCS)2](2) isomer by solvothermal induced isomerization method. Single-crystal diffraction data was collected at 293 K by CAD-4 diffractometer. Complex (1) crystallizes in the monoclinic space group C 2/c with Z=4, a=14.828(4), b=11.485(5) Å ,c=15.071(2) Å, beta = 110.081(15) deg. The bond lengths of Fe-N are 2.249(4) Å, 2.197(4) Å, and 2.056(5) Å for complex 1 and 2.217(2) Å, 2.181(2) Å, and 2.097(3) Å for complex 2 at HS state. Solvothermal methods have provided rotes to otherwise inaccessible geometry isomers. Both complexes have a similar pseudo-octahedral [FeN6] core with the NCS- groups in the cis arrangement in 1 but trans in 2.
Another Dinuclear (N`, N1, N2 ,N``)2 Double bridging complex [Fe2(bpt)2(NCS)2(CH3OH)2] (3) and unique spin crossover 1D ladder complex [Fe2(bpt)2(NCS)2(bpy)2]•MeOH (4) have been synthesized successfully also by solvo- thermal syntheses from spin crossover trans-[Fe(abpt)2(NCS)2] complex.
Variable-temperature magnetic susceptibility measurement reveals that 1 and 3 staying in a high-spin state in the observed temperature range of 5-300 K. The 1D Spin-crossover complex 4 has a abrupt spin transition at 130 K and possesses unusual magnetic behavior.
It is interesting to note that the steric possible conformation can be realized by hydro-(solvo-)thermal syntheses and the differences of the crystal packing and [FeⅡN6] octahedron geometry between these iron (Ⅱ) complexes result in a dramatic change in their magnetic properties. Further studies on the origin of the discrepancy in the crystal field responsible for this result are currently in progress.

並列關鍵字

solvothermal ； spincrossover ； iron

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