A bidentate ligand N,Nâ²- bis(3-pyridinecarboxamide)-1,6-hexane (L) and its silver complexes have been synthesized and characterized by single crystal X-ray diffraction. Reaction of AgClO4 and L in H2O/EtOH gives rise to a coordination polymer [Ag2L3OH][ClO4]·2.5H2O. The X-ray crystal structure of the compound shows honeycomb-like networks in which four-coordinated Ag ions are linked to three-coordinated Ag ions via three ligands L. The coordination of the long ligands L to the Ag ions creates tube-like structures and the tubes of adjacent honeycomb layers are interlocked, leading to an interpenetrating network. The compound [AgL][ClO4], synthesized from CH3OH, is composed of twisted zigzag coordination polymers in which ligands L are linked by Ag ions. Ligand L displays two different conformations A and B within a single strain of polymer. The two conformers differ in the orientation of the two pyridyl-groups which are arranged periodically in the polymer in the sequence ABBABBA. The polymer chains assemble into 2-D undulating sheets via amide hydrogen bonds. Reaction between AgNO3/AgCF3SO3 and L leads to polymeric compounds [AgL][NO3] and [AgL][CF3SO3]. The compounds are composed of coordination polymers in zigzag conformation and the polymer chains assemble into undulating sheets via inter-chain hydrogen bonds. The inter-sheet AgâAg distances of the compounds are in the order [AgL][CF3SO3] > [AgL][ClO4] > [AgL][NO3]. The anion exchange properties of the compounds are monitored by using X-ray powder diffraction, infrared spectroscopy and elemental analysis. Our results show that the anions in [AgL][NO3] and [AgL][CF3SO3] can be totally replaced with ClO4â. However, the exchange is not reversible. In additional, inter-conversion between [AgL][NO3] and [AgL][CF3SO3] by anion exchange is shown to be unfeasible. Anion selectivity could be due to the different hydration energy of the anions and the structural reorganization involved in the conversion.
我们合成了一种双齿
配体 N,Nâ²-双(3-
吡啶甲酰胺)-1,6-己烷(L)及其
银配合物,并利用单晶 X 射线衍射法对其进行了表征。Ag 和 L 在
H2O/EtOH 中反应生成了配位聚合物 [Ag2L3OH][ ]Â-2.5 。该化合物的 X 射线晶体结构显示出蜂窝状网络,其中四配位的 Ag 离子通过三个
配体 L 与三配位的 Ag 离子相连。由 CH3OH 合成的化合物 [AgL][ ]是由
配体 L 与 Ag 离子连接的扭曲之字形配位聚合物组成。
配体 L 在单株聚合物中呈现出 A 和 B 两种不同的构象。这两种构象在两个
吡啶基的取向上有所不同,这两个
吡啶基按照 A
BBABBA 的顺序在聚合物中周期性地排列。聚合物链通过酰胺氢键组合成二维起伏片。AgNO3/AgCF3SO3 与 L 反应生成聚合物 [AgL][NO3] 和 [AgL][CF3SO3]。这些化合物由之字形构象的配位聚合物组成,聚合物链通过链间氢键组合成起伏的薄片。化合物的片间 AgâAg 距离顺序为 [AgL][CF3SO3] > [AgL][ ] > [AgL][NO3]。利用 X 射线粉末衍射、红外光谱和元素分析监测了这些化合物的阴离子交换特性。结果表明,[AgL][NO3]和[AgL][CF3SO3]中的阴离子可以完全被
ClO4 取代。但是,这种交换并不可逆。此外,阴离子交换法在[AgL][NO3]和[AgL][CF3SO3]之间的相互转化也不可行。阴离子选择性可能是由于阴离子的
水合能不同以及转换过程中涉及的结构
重组。