3d過渡金屬錯合物之鍵性研究

Abstract

本論文主要利用多極模型精算方式處理由低溫X光單晶繞射儀器實驗，得到的錯合物晶體結構因子，以獲得分子的總電荷密度分佈，再輔以分子軌域計算與密度泛函數理論計算方法，描述一系列以3d過渡金屬為中心的錯合物分子中，原子與原子相互間鍵結的電子組態。 論文中第一系列錯合物是以Cu原子為中心的三個錯合物，分別是[CuI(phen)(μ-NCS)]、[CuII2(phen)2(NCS)2(μ-OH)2•2H2O]及[CuII(phen)2(NCS)2]，此三個分子具有相同(phen)與(NCS)配位基，但是中心Cu原子分別為四、五及六配位三種不同的配位環境，經多極模型精算分析與拓樸學分析的結果，顯示金屬與配基Cu-L鍵結的鍵性，其中從Laplacian的數值為正值(3.90(1) ~ 12.28(1) e/Å5)，以及總能量密度數值為負值(-0.11 ~ -0.46 Hartree/Å3)兩種指標，Cu-L鍵性為具過渡封閉性殼層作用性質的極性共價鍵鍵性，另藉由拓樸學上量化的數據分析，也觀測到分子與分子間微弱作用力的鍵性，如氫鍵，π－π堆疊等電子分佈性質。 第二系列錯合物分別是[FeIII(C5H4NHCOO)(μ-SO4)(μ-OH) (H2O)]錯合物以及 [MII(C5H4NCOO)2(H2O)4], ( M = Mn, Fe, Co, Ni, Cu, Zn )錯合物，此系列錯合物是由一系列3d過渡金屬與尼古丁酸分子所形成具相同配位環境的同型異構物，主要目的是藉由固定金屬原子週邊配位基，更換錯合物上不同的金屬原子方式，模擬探討在配位環境不變情形時金屬原子的氧化價態變化後的金屬—配基間的鍵性性質。經由多極模型精算與拓樸學方法的分析後，對於金屬-配基鍵結的部分可以觀察到，配位基分子為σ-電子施予者連接金屬的原子上的電子是集中指向金屬原子方向，而金屬則為σ-電子接受者，相同的從數值為正值的Laplacian ( 3.22(1) ~ 12.08(1) e/Å5)，以及總能量密度數值為負值(-0.01 ~ -0.12 Hartree/Å3)兩種指標，可知金屬-配基鍵的鍵性為極性共價鍵的性質，另外依據此系列錯合物的晶體結構數據資料、多極模型精算以及拓模學計算等分析結果，3d金屬部分顯示出有離子半徑收縮以及銅金屬錯合物的Jahn-Teller形變的特性。

A series of 3d transition metal complexes were investigated in this dissertation, of which bonding characteristics and the electronic configuration of metal centers were pursued. Single crystal X-ray diffraction experiment at low temperature was applied. An aspherical multipole model was introduced subsequently to give a better description of total electron density distribution, based on which topological analysis was also carried out. Molecular orbital calculations and single-point theoretical calculations at density-functional-theory level (DFT) were performed as well for comparison. In the first part three Cu-complexes, [CuI(phen)(μ-NCS)], [CuII2(phen)2(NCS)2(μ-OH)2•2H2O] and [CuII(phen)2(NCS)2], were studied. Though, same ligands (phen and NCS-) were found in all three compounds, of which local environments around Cu centers were different (coordination number = 4, 5 and 6, respectively). All Cu-ligand bonds are classified as transit closed-shell interaction (or polarized covalent bond) according to the corresponding positive Laplacian ( 3.90(1) ~ 12.28(1) e/Å5) and negative total energy densities ( -0.11 ~ -0.46 Hartree/Å3) given by the topological analysis. In addition, weak interactions such as hydrogen bonds and π-π stacking interactions were observed as well supported by the numerical evidence on the bond path. In the second part a series of complexes constructed by 3d transition metal and nicotinic acid ([FeIII(C5H4NHCOO)(μ-SO4)(μ-OH)(H2O)] and [MII(C5H4NCOO)2(H2O)4] where M = Mn, Fe, Co, Ni, Cu, Zn) were investigated. In these iso-structural compounds different metal centers are crystallized in roughly the same local coordination environment, of which the oxidation states and the corresponding bonding characteristics (M-L) are inspected. Local charge concentrations addressed on atoms in the first coordination shell are clearly toward metal centers showing the σ-donor behavior. All the metal-ligand bonds in these complexes are also classified as transit closed-shell interaction due to the positive Laplacian ( 3.22(1) ~ 12.08(1) e/Å5) and negative total energy densities ( -0.01 ~ -0.12 Hartree/Å3). Besides, wd-block contraction of the 3d transition metal centers and the Jahn-Teller distortion around Cu ones were observed as well.