鎳,銅錯合物及含硒樣品之電子組態研究: 電子密度分析及X光吸收光譜

Abstract

一系列以含硫且具自身氧化能力的配位基MNT (maleonitriledithiolate； S2C2(CN)2)所形成的金屬-硫錯合物(PyH)z[M(MNT)2] (M = 鎳、銅；z = 2、1)，展現了位置選擇性的氧化還原性質。金屬的K-edge及L-edge X光吸收光譜分別對鎳與銅金屬氧化態提供了直接的證據。在鎳錯合物的系統中，氧化還原反應發生在具自身氧化還原能力的配位基上(Ligand-Based)。相反地，在銅的錯合物系統中，氧化還原反應發生在金屬銅本身(Metal-Based)。此外，硫的X光吸收光譜配合DFT計算亦提供了金屬-硫鍵結的資訊，結合鎳、銅金屬及硫的X光吸收光譜結果確認了此系列樣品的氧化還原性質。經由高解析的低溫X光單晶繞射數據所得到的電子密度分析，藉由變型電子密度分析及鍵臨界點的拓樸分析也提供了金屬-配位基的鍵結特性。由多極模型導出的金屬d軌域電子分佈及monopole charge皆驗證了XAS所提出的氧化還原性質。 含第四週期元素硒原子之樣品的電子密度研究：第一個樣品為3,4-trimethylene-6a-selenaselenophthene，此分子包含了一接近線型排列且具有三中心四電子鍵結特性的三核硒鏈型部分。第二個樣品為平面四方形的鎳-硒錯合物Ni[Se2P(O-iPr)2]2，其分子間具有微弱的硒-硒作用力(3.294A)，有趣地，透過分子內及分子間的硒-硒作用力形成了平面四方的硒原子網狀結構，結合拓樸分析及Hirshfeld surface證實了微弱的分子間硒-硒作用力。 為了合理解釋以atr (azotriazole)為架橋配位基的三維及二維自旋交叉錯合物Fe(atr)3(ClO4)2•2H2O與Fe(atr)(pyz)(NCS)2 之兩階段自旋交叉的磁行為與結構的關係，進行了詳細的磁性量測實驗，證實三維系統中兩階段的磁行為是取於晶格中溶劑分子的存在與否，且二維與三維的樣品皆明顯地展現出晶格中的溶劑分子影響磁行為改變的溫度，溶劑影響自旋交叉現象的也成功地利用X光單晶結構解析加以證明。

A series of metal-sulfur square planar complexes, (PyH)z[M(MNT)2], where M = Ni and Cu, MNT a non-innocent ligand maleonitriledithiolate, [S2C2(CN)2]z-, z=2, 1, are synthesized in order to characterize the site-selected oxidation-reduction properties. Metal K-edge and L-edge X-ray absorption spectroscopy(XAS) are used to deliver the direct evidence for the oxidation state of metal ion. It is clearly demonstrated that redox reaction takes place in the ligand (Ligand-Based) for Ni complexes but in the metal (Metal-Based) for the Cu complexes. In addition, the sulfur K-edge absorption together with the DFT calculation gives a clear picture on the covalency of M-S bond. With the XAS of metal and S, the oxidation reduction site is firmly established for Cu and Ni complexes. The charge density studies from high resolution single crystal X-ray diffraction measurements at 100K are also investigated to aim at the understanding on the nature of the metal-ligand bond in terms of deformation densities and topological properties associated with the bond critical points (BCP). The d-Orbital populations of metal ion derived from multipole model and the monopole charge thus obtained are agreeable with the redox properties established from XAS. Charge density studies on Se-containing compounds are undertaken: 3,4-trimethylene-6a-selenaselenophthene contains a linear tri-selenium chain in the molecule, which exhibits a three-centered four-electron bond for Se-Se-Se part. A square planar Ni complex bonded with four selenide ligands, Ni[Se2P(O-iPr)2]2 is studied. Ni-Se bonds are characterized together with the short intermolecular Se-Se contact of 3.294 A. Interestingly, there is a Se square network in the crystal through the intra- and inter- molecular Se×××Se contacts. Such contacts are first characterized by topological analysis and Hirshfeld surface mapping. The magnetic measurements of three-dimensional and two-dimensional atr-based Fe(II) spin crossover (SCO) framework systems (Fe(atr)3(ClO4)2•2H2O and Fe(atr)(pyz)(NCS)2•4H2O) are studied in detail in order to solve the puzzle of the stepwise spin transition phenomena. It is found that the stepwise transition is due to the loss of water molecules in the lattice, where the hydrated/dehydrated forms of 2D and 3D systems apparently exhibit quite different transition temperatures. The solvent-dependent spin crossover phenomena in these structures are systematically demonstrated.