鐵二價之偶氮三唑自旋交叉錯合物合成與鑑定

Abstract

合成一新穎並具雙配位性質的配基，此配基是藉由偶氮連接兩端 的三唑基團形成一共平面結構。兩端的三唑基團都具有配位性質因此成為合成多維度自旋交叉錯合物的理想配基。我們藉由不同比例的反應條件或者搭配其他配位配基方式順利合成出1D、2D 以及3D 的錯合物。一維系統是以水分子和NCS 等配基搭配atr 形成，在二維系統則是改採吡阱配基和NCS、atr 等配位形成二維層狀結構，層和層之間則互為交錯結構，分子式為[Fe(µ-atr)(µ-pyz) (NCS)2]．4H2O。三維錯合物分子式為[Fe(µ-atr)3](ClO4)2．2H2O，結構互為交錯連結，陰離子和水分子則位於連接孔洞中。以atr 配基所形成的錯合物都具特殊磁性性質。一維錯合物具有鐵磁性質，居里溫度為6 K。二維和三維則具有自旋交叉性質。二維錯合物相轉變溫度為227 K，具有5 K 的磁滯曲線。三維錯合物則具兩階段的磁性變化，相轉變溫度分別為276K 和259K，在261 K~269 K 具有另一平緩階段變化。我們分別對二維高自旋、低自旋狀態和三維的265 K 及高、低自旋狀態進行晶體和吸收光譜另外輔以熱分析進行實驗。

A new ligand, trans-4,4`-azo-1,2,4-triazole (atr) was designed and synthesized to construct the possible candidates for spin crossover system. The ligand is a planar molecule with two 1,2,4-triazole linked by an azo group. It could be served as a multi-dentate ligand or a good linkage ligand. A series of Fe(II) polymeric compounds in 1D, 2D and 3D frameworks have been successfully synthesized and studied structurally and magnetically. The crystal structures of the ligand and the series of polymeric Fe(II) complexes will be presented. In all the complexes, each ligand atr serves as a bridge between two Fe(II) centers; There are water molecules and NCS ligand around each Fe(II) in the 1-D polymeric compound, [Fe(µ-atr)(NCS)2(H2O)2]; An additional bridge ligand,pyz, is used to form a rectangular 2D framework, [Fe(µ-atr)(µ-pyz)(NCS)2]．4H2O. A cationic species with Fe to atr ratio of 1 to 3 is formed in a 3D framework with the perchlorate as the inclusion counter anions,[Fe(µ-atr)3](ClO4)2．2H2O, the structure shows a interlock network. The magnetic properties are quite interesting: It is ferromagnetic for the 1D system but display spin transitions for both 2D and 3D systems. It exhibits an abrupt spin transition at Tc= 227 K for [Fe(µ-atr)(µ-pyz)(NCS)2]．4H2O. However, it shows a two-step spin transition for the 3D frameworks [Fe(µ-atr)3](ClO4)2．2H2O. The crystal structures at various spin states will be compared.