本文分三個部分，首先以β-雙酮類(L1)，合成一系列的Fe2Ln2的四核混金屬化合物，此類化合物中心以一個μ4的氧原子作為架橋，連接起這四個金屬核，而兩個鑭系金屬皆為扭曲的十二面體。在直流(dc)磁化率的測量下，顯示兩個鐵三價的金屬存在著很強的反鐵磁(antiferromagnetic)作用力。而在未外加直流磁場條件的交流磁化率(ac)測量當中，鏑(dysprosium)及鈥(holmium)的類似物皆有觀測到磁緩現象(slow magnetic relaxation)，其中在化合物2•Dy的磁異向能障(Ueff)超過180 K，是目前發現的鐵(III)-鑭系單分子磁鐵中最高的。而在第二部份我們同樣也用兩種β-雙酮類(L2和L3)合成出一系列Fe4Ln2的六核結構。此六個化合物都是存在著一個中心的{Fe4Ln2O10(CO2)2}核，且四核的鐵組成一個近共平面的單元，鑭系金屬則是以一個八配位、扭曲雙面三角棱柱的構型。從直流磁化率的測量發現此Fe4的單元具有很強的反鐵磁交互作用，而在交流磁化率的測量中10•Dy也有很高的磁異向性的表現，不外加磁場下，化合物7•Tb和8•Ho也觀測到明顯的磁緩現象。最後一個章節中，我們介紹以β-雙酮類(L4)合成一系列之前從未發現的Fe2Ln4的混金屬六核化合物，這個化合物的結構有點類似於第二章的結構，但是原本鑭系金屬的位置被置換成鐵金屬，中間的Fe4單元也變成Ln4。此結構中有兩個不同配位環境的鑭系金屬，分別是八配位的扭曲雙面三角棱柱(biaugmented trigonal prism)及九配位介於單帽反四角棱柱(mono-capped square antiprism)、三面三角棱柱(spherical tricapped trigonal prism)及馬芬蛋糕(muffin)的幾何構型，直流磁化率的測量顯示此類化合物有反鐵磁的作用，也以居禮-外斯定律(Curie-Weiss law)得到θ值皆小於零，表示分子間也存在著反鐵磁的交互作用，在交流磁化率中，只有在含高磁異向性的鑭系中(如鋱(terbium)及鏑(dysprosium))觀測到磁緩的現象。

This work contains three parts. First, a new family of heterometallic tetranuclear Fe2Ln2 (Ln = Y, Dy, Ho and Er) complexes were synthesized using the β-diketone ligand, L1. Four metals are linked together with a μ4−O atom. The geometries of both lanthanides are distorted triangular dodecahedron. The dc magnetic studies reveal that the presence of strong antiferromagnetic interaction between two Fe3+ ions. Dynamic magnetic susceptibility measurements indicate that slow relaxation of magnetization is present in dysprosium(III) and holmium(III) analogues at the absence of external dc field. Moreover, complex 2•Dy possesses the highest energy barrier (Ueff), over 180 K, among all the FeIII–LnIII SMMs to date. For the second part, a series of Fe4Ln2 compounds were synthesized using two different β-diketone ligands L2 and L3 ([FeIII4LnIII2(μ4-O)2(μ2-OMe)2(μ2-OH)2(L2)4 (OAc)2Cl2(MeOH)2]Cl2•2MeCN•xH2O (Ln = Y (5•Y), Gd (6•Gd), Tb (7•Tb), Ho (8•Ho) and Er (9•Er)) and [FeIII4DyIII2(μ4-O)2(μ2-OMe)4(L3)4(OAc)2Cl2(H2O)2] Cl2•10H2O (10•Dy)). All these seven complexes possess a {Fe4Ln2O10(CO2)2} core with a strictly coplanar Fe4 unit. The lanthanides possess distorted biaugmented trigonal prismatic geometries. Static magnetic susceptibility measurements show that the dominant antiferromagnetic interactions within Fe4 unit. In the alternating current magnetic measurements, complex 10•Dy also possesses a larger reversal magnetization barrier. The phenomenon of slow magnetic relaxation was also observed in complexes 7•Tb and 8•Ho under a zero dc filed. In the final chapter, the unprecedented heterohexnuclear FeIII–LnIII clusters (Ln = Y (11•Y), Gd (12•Gd), Tb (13•Tb) and Dy (14•Dy)) were synthesized using β-diketone ligand, L4. The structure model is similar to the Fe4Ln2 compounds mentioned in previous section. In contrast to the last chapter (Fe4Ln2) with the complexes herein (Fe2Ln4), the two lanthanides were replaced by irons and the coplanar Ln4 unit is in the central position. Different coordination spheres on the two individual lanthanides, one is eight-coordinated (biaugmented trigonal prism) while the other is nine-coordinated (among mono-capped square antiprism, spherical tricapped trigonal prism and muffin). Direct current (dc) susceptibility measurements indicate that the presence of antiferromagnetic interactions for four complexes. The Curie-Weiss equation also suggests that the intermolecular antiferromagnetic interactions due to the negative Weiss constant (θ). Alternating current (ac) magnetic susceptibility studies show that only composing highly anisotropic lanthanides, e.g. TbIII and DyIII, exhibit slow magnetic relaxation.

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