含2,6-二甲酰胺基吡啶单元的大环合成、结构及其对四面体构型阴离子的络合性质

采用前体二胺N,N’-(3-胺基苯基)-2,6-二甲酰亚胺吡啶(1)和5,5’-亚甲基双水杨醛(2)进行缩合反应得到含酚羟基的 1+1] 席夫碱大环L1, 将其中席夫碱C=N双键还原得到环状骨架更具柔性的饱和大环L2. 通过1H NMR、FABMS和元素分析等对大环组成进行了表征, 并通过X射线单晶衍射解析了两个大环的晶体结构. 采用UV-Vis 光谱滴定技术对大环与系列阴离子的络合作用进行了考察, 结果表明席夫碱大环L1对四面体构型的阴离子H2PO4-、 HP2O73-和H2P2O72-有明显的选择性识别作用, 进一步通过UV-Vis 光谱、核磁滴定等技术获得了识别反应的配位比及平衡常数(K), L1对3个磷酸阴离子的络合能力依H2PO4-、HP2O73-和H2P2O72-顺序递增。

Syntheses and Structures of Macrocycles Containing 2,6-Diamidopyridine Unit and their Complex Properties for Tetrahedral Anions

1+1] Schiff base macrocycle L¹ was synthesized from the reaction of precursors N,N''-bis(3-aminophenyl)-pyridine-2,6-dicarboxamide (1) with 5,5''-methylene-bis-salicylaldehyde (2), and furthermore the macrocycle L¹ was reduced to the corresponding saturated macrocycle L². The two macrocycles were characterized by ¹H NMR, FABMS spectroscopies and elemental analysis, and their crystal structures were determined by X-ray diffraction analysis. The two macrocycles exhibited non-planar structures, and L² showed a more flexible twisted conformation. The complexation of macrocycles with a series of anions was investigated by UV-Vis spectrometric titration technology. The results showed that L¹ had obvious selective recognition ability for tetrahedral anions H₂PO₄^-, HP₂O₇^3-, and H₂P₂O₇^2-, respectively. Properties of the 1+1] Schiff base macrocycle L¹ hydrogen-bonding interactions with these tetrahedral anions were investigated using UV-Vis and ¹H NMR titration, respectively. The stoichiometric ratio and binding constant (K) of the interaction were obtained. The results demonstrated that L¹ binded the three anions with a 1:1 binding stoichiometry, and the bonding constants (K_a) increased in the order of H₂PO₄^-, HP₂O₇^3-, H₂P₂O₇^2-.