修飾二吡啶胺配基及其直線型三核鎳金屬串錯合物之合成與研究

Abstract

本論文研究內容為吡啶噻唑胺(Hpta 2-pyridyl-2’-thiazolylamine)與吡啶奎林胺(Hpqa 2-pyridyl-2’-quinolinylamine)配基之直線型三核鎳金屬串錯合物合成、結構分析、磁性及其電子吸收光譜之探討。 首先，合成出吡啶噻唑胺(Hpta)與吡啶奎林胺(Hpqa)配基，經由紅外線光譜、1H NMR與快速原子撞擊質譜(FAB-MS)確認配基的組成，將其與Ni(OAc)2•4H2O高溫萘燒，加入NaSCN當作軸向配基之來源，可得到三核鎳金屬串錯合物[Ni3(μ3-pta)4(NCS)2]與(2,2)-cis form [Ni3(μ3-pqa)4(NCS)2]；在常溫下以NaCN可置換NCS-分別得到[Ni3(μ3-pta)4(CN)2]與(2,2)-cis form [Ni3(μ3-pqa)4(CN)2]。 由X-ray 單晶繞射解析可知，四個pta-或pqa-配基以全順向式之配位模式與鎳離子鍵結；中間鎳離子與四個胺基鍵結成四配位形式，兩端鎳離子則為五配位形式。此外，pta-與pqa-配基均為不對稱配基，因此造成三核鎳金屬串錯合物有異構物的存在，pta-配基合成出的三核鎳金屬串錯合物分子結構在結晶學上會有吡啶與噻唑互相重疊產生失序(disorder)的情形，無法分辨出實驗得到的是屬於哪一種構型。pqa-配基則沒有此類問題，從單晶構造上得知[Ni3(μ3-pqa)4(NCS)2]與[Ni3(μ3-pqa)4(CN)2]均為(2,2)-cis form，吡啶與奎林並沒有失序的問題。 磁性結果得知，上述三核鎳金屬串錯合物均為反鐵磁性物質，利用末端鎳離子為高自旋電子組態(S = 1)及中間鎳離子電子組態為低自旋(S = 0)去擬合，可得到偶合常數約-76.4 ~ -108.8 cm-1，與X-ray單晶繞射解析中Ni-Ni距離相互比較，符合Ni-Ni距離愈短，偶合常數愈大的趨勢。 經由循環伏安法則發現[Ni3(μ3-pta)4(NCS)2]在+1.6 ~ -0.8 V沒有觀察到氧化還原電位；(2,2)-cis form [Ni3(μ3-pqa)4(NCS)2]則在+0.66 V與-0.76 V各有一組氧化還原峰。 另一方面，利用pqa-配基合成出軸向配基為Cl-的三核鎳金屬串錯合物(4,0) form [Ni3(N-μ3-pqa)3(C-μ3-pqa)Cl](PF6)，符合改變較大之軸向配基能合成出(4,0) form之推測；從X-ray單晶繞射解析與紅外線光譜亦發現有C-H活化現象。 (4,0) form [Ni3(N-μ3-pqa)3(C-μ3-pqa)Cl](PF6)的磁性結果在300 K時，有效磁矩為2.86 B.M.，與一個鎳離子(II)為獨立之高自旋電子組態(S = 1)之純自旋理論μeff = 2.828 B.M.相當接近。電子吸收光譜結果則發現(4,0) form與(2,2)-cis form吸收位置與強度均有明顯差異。

The aim of this thesis is to investigate the synthesis, structures, and correlative properties of linear trinickel metal string complexes, where the ligands are 2-pyridyl-2’-thiazolylamine (Hpta) and 2-pyridyl-2’- quinolinylamine (Hpqa). Hpta and Hpqa ligands have been synthesized and characterized by various techniques. Linear trinickel metal string complexes, [Ni3(μ3-pta)4X2] (X = NCS, CN) and (2,2)-cis form [Ni3(μ3-pqa)4(NCS)2] (X = NCS, CN), have also been synthesized and characterized. The X-ray structural studies reveal the terminal nickel ions with five-coordinate and the inner nickel ion with four-coordinate. Due to asymmetrical Hpta and Hpqa ligands, trinickel metal string complexes may have several isomers. However, the pyridyl ring and the thiazolyl ring determined by X-ray diffraction are undistinguishable and a series of [Ni3(μ3-pta)4X2] (X = NCS, CN) are all disorder in crystallography. A series of (2,2)-cis form [Ni3(μ3-pqa)4(NCS)2] (X = NCS, CN) are the (2,2)-cis form without disorder in crystallography. The magnetic results show that the trinickel metal string complexes all are antiferromagnetic compounds with the coupling constant in the range of -76.4 to -108.8 cm-1. While the Ni-Ni distances increase, the coupling constants decrease significantly. Cyclic voltammetrical data shows that [Ni3(μ3-pta)4(NCS)2] exhibits no potential between +1.6 and -0.8 V whereas (2,2)-cis form [Ni3(μ3-pqa)4(NCS)2] exhibits one oxidative potential at +0.66 V and one reductive potential with ligands at -0.76 V. Additionally, (4,0) form [Ni3(N-μ3-pqa)3(C-μ3-pqa)Cl](PF6) has been synthesized and characterized by various spectroscopic techniques. X-ray structural studies show that C-H activation is occurred in the complex and Ni-Ni distances are 2.407(1), 2.361(1) Å, respectively. Four quinolinyl rings of the compound are faced toward the same way ((4,0) form). One of terminal Ni2+ ions is bounded to the chloride ion as the axial ligand. IR spectra shows ν(N-H) = 3390 cm-1, ν(PF6-) = 844 cm-1. Magnetic measurement shows μeff = 2.86 B.M. at 300 K which belongs to paramagnetism of the high spin (S = 1) Ni2+ ion. The electronic absorption spectra indicate that there are obviously different wavelengths between the (4,0) form [Ni3(N-μ3-pqa)3(C-μ3-pqa) (NCS)](PF6) and (2,2)-cis form [Ni3(μ3-pqa)4(NCS)2].