Syntheses and Studies of Linear Multinuclear Nickel String Complexes with the Oligo-α-pyridylamino Ligands

合成一系列多吡啶胺配基(oligo-α-pyridylamino ligands)，並開發新的錯合物合成法，成功合成出多種配位模式之直線型三核、四核、五核、六核以及七核鎳金屬串錯合物，而新型配位模式之錯合物可以經由軸向配基(axial ligand)或分子間氫鍵自組裝得到一維與二維超分子化合物。
五氮配基(H2tpda)與不同鎳(Ni2+)金屬起始物反應，分別得到特殊不對稱型四核鎳與對稱型五核鎳金屬串錯合物，由於結構上的差異，磁性量測結果顯示在四核鎳錯合物兩末端鎳離子具有鐵磁性作用，而五核鎳錯合物則有反鐵磁作用。
中性與一個電子氧化之七核鎳金屬串錯合物[Ni7(teptra)4XY]Z (X ,Y = axial ligands, Z = anions)，其結構為四個七氮配基(teptra3-)以全順向式(all syn form)配位構型螺旋環繞七個直線型排列的鎳離子。其中七核鎳氧化物 [Ni7(teptra)4Cl2](PF6)、[Ni7(teptra)4(NCS)2](BF4)為對稱型，一個電子氧化在中間鎳離子上，而[Ni7(teptra)4(H2O)(ClO4)](ClO4)2為不對稱型，一個電子氧化在末端鎳離子上，與磁性結果相吻合。氧化物鎳-鎳之間的距離短於中性錯合物，表示七核鎳氧化物含有部分金屬-金屬鍵結，此結果可望應用於奈米金屬導線以及分子開關上。
雙配基三核鎳[Ni3(H2peptea)2](OTf)2、[Ni3(H3hxppea)2](OTf)2與五核鎳錯合物[Ni5(H2hephxa)2](ClO4)2的多氮配基都以特殊夾子(clip)狀之新型配位模式螺旋環繞鎳離子(Ni2+)，並且依比例將三氮(Hdpa)、九氮(H4peptea)配基與鎳離子反應，得到混配基三核鎳錯合物[Ni3(dpa)2(H2peptea)X]n+ (X = CH3CN, n = 2 ; X = NCS-, n = 1)，經由自組裝可以得到二聚物[{Ni3(dpa)2(H2peptea)}2(fumarato)](ClO4)2。

The syntheses of the novel oligo-α-pyridylamino ligands and their linear multinuclear nickel string complexes are reported. The tri-, tetra-, penta-, hexa- and heptanuclear nickel chain and supramolecular assembly of tri-nickel complexes have been synthesized.
The structures of tetra-nickel complexes, [Ni4(Htpda)(tpda)3NCS] and [Ni4(Htpda)(tpda)3](ClO4), containing tetranickel in a chain, which are helically wrapped by one Htpda- and three tpda2- ligands. The magnetic moment of the two terminal nickel displays ferromagnetism.
The crystal structures of the neutral and one-electron oxidized hepta-nickel complexes, [Ni7(teptra)4XY]Z (X and Y is axial ligands, Z is anions), provide the linear heptanickel chain is helically wrapped by four all syn type teptra3- ligands. The symmetrical Ni7 unit of oxidized complexes [Ni7(teptra)4Cl2](PF6) and [Ni7(teptra)4(NCS)2](BF4) reveal the one-electron oxidation may occur over the internal(inner) Ni5 unit. The unsymmetrical Ni7 unit of oxidized one [Ni7(teptra)4(H2O)(ClO4)](ClO4)2 reveals the one-electron oxidation occurs at the terminal Ni(7) ion. All of the oxidized compounds show stronger Ni-Ni interactions with shorter Ni-Ni distances as compared to those of the neutral compounds.
The structures of the tri- and penta-nickel complexes, [Ni3(H2peptea)2] (OTf)2, [Ni3(H3hxppea)2](OTf)2, [Ni3(dpa)2(H2peptea)X]n+ (X = CH3CN, n = 2 ; X = NCS-, n = 1) and [Ni5(H2hephxa)2](ClO4)2, provide the linear nickel chain is helically wrapped by novel clip-like type ligands. Supramolecular assembly of tri-nickel complexes [Ni3(dpa)2(H2peptea)CH3CN](ClO4)2 obtain a dimer, [{Ni3(dpa)2(H2peptea)}2(fumarato)](ClO4)2.The magnetic moments of the two terminal nickel display antiferromagnetic coupling.