Subtle Structural Changes in Coordination Chains: Influence of the Flexibility of the Precursor Ligands and of the Solvent

A novel flexible ligand dpap·2H2O (1) (dpap = 2,6-(N,N‘-di(4-pyridyl)amino)pyridine) and its five related coordination
polymers {[Cu(dpap)(OAc)2]·CH3CN}n (2·CH3CN), {[Cu(dpap)(OAc)2]·0.25CH2Cl2}n (2·0.25CH2Cl2), {[Cu(dpap)(OAc)2]·CHCl3}n
(2·CHCl3), {[Cu(dpap)(OAc)2]·0.5CH3OH}n (2·0.5CH3OH), and {[Cu(dpap)(maa)2]·2CH3OH}n (3·2CH3OH) (Hmaa = 2-methyl-acrylic acid) have been synthesized and structurally characterized by X-ray crystallography. The networks showed a lack of dependence
on the nature of the counterion and solvent. Compound 2·CH3CN consists of uncoordinated guest CH3CN molecules and a one-dimensional (1D) zigzag chain. The diffusion in the CH2Cl2 solvent system results in a 1D helical chain of 2·0.25CH2Cl2, and that
in CHCl3 system leads to a meso-helix chain [Cu(dpap)(OAc)2] motif of 2·CHCl3. The overall structure of 2·0.5CH3OH was found
to be similar to that of 2·0.25CH2Cl2 despite the presence of different solvent molecules. The volumes of the channels are as
follows:  2·CHCl3 > 2·0.25CH2Cl2 > 2·CH3CN > 2·0.5CH3OH. Using an maa group instead of an OAc- anion, we obtained
polymer 3·2CH3OH, which displays a topological meso-helix chain.

一种新型柔性配体dpap·2H₂O(1)（dpap=2,6-二(N,N'-二(4-吡啶基)氨基)吡啶）及其五种相关配位聚合物{[Cu(dpap)(OAc)₂]·CH₃CN}ₙ(2·CH₃CN)、{[Cu(dpap)(OAc)₂]·0.25CH₂Cl₂}ₙ(2·0.25CH₂Cl₂)、{[Cu(dpap)(OAc)₂]·CHCl₃}ₙ(2·CHCl₃)、{[Cu(dpap)(OAc)₂]·0.5CH₃OH}ₙ(2·0.5CH₃OH)以及{[Cu(dpap)(maa)₂]·2CH₃OH}ₙ(3·2CH₃OH)（Hmaa=甲基丙烯酸）已被合成，并通过X射线晶体学完成结构表征。此类配位聚合物的骨架网络与抗衡离子及溶剂的种类无关。化合物2·CH₃CN由未配位的客体CH₃CN分子与一维（1D）锯齿链构成。在二氯甲烷溶剂体系中经扩散得到的2·0.25CH₂Cl₂呈现一维螺旋链结构；而在三氯甲烷溶剂体系中得到的2·CHCl₃则拥有以[Cu(dpap)(OAc)₂]为基元的内消旋螺旋链结构。尽管溶剂分子种类不同，2·0.5CH₃OH的整体结构仍与2·0.25CH₂Cl₂高度相似。各体系的孔道体积大小依次为：2·CHCl₃ > 2·0.25CH₂Cl₂ > 2·CH₃CN > 2·0.5CH₃OH。以甲基丙烯酸根替换乙酸根（OAc⁻）后，得到聚合物3·2CH₃OH，其展现出拓扑学意义上的内消旋螺旋链结构。