Syntheses and Crystal Structures of a Series of Zn(II)/Cd(II) Coordination Polymers Constructed from a Flexible 6,6′-Dithiodinicotinic Acid

Five novel Zn(II)/Cd(II)-based coordination polymers 1–5 with a flexible disulfide derivative of the nicotinate 6,6′-dithiodinicotinic acid (H2cpds) and two rodlike N,N′-donor ligands (bpa =1,2-bi(4-pyridyl)ethane; bpp = 1,3-bis(4-pyridyl)propane) have been successfully synthesized under the liquid diffusion condition and characterized by elemental analysis, IR spectra, and X-ray diffraction, namely {[Zn(cpds)]·H2O}n (1), {[Zn(cpds)(bpa)0.5]}n (2), {[Zn(cpds)(bpp)]}n (3), {[Cd(cpds)(bpa)1.5]·H2O}n (4), and {[Cd2(cpds)2(bpp)·(H2O)3]·4H2O}n (5). Complexes 1–5 display various coordination motifs due to different conformations, and coordination modes of the H2cpds ligand, at the same time the effect of the auxiliary ligands plays important roles in the construction of extended supramolecular networks. Complexes 2–4 all exhibit 2D layer structures, in which 2 displays a 2-fold 2D → 2D parallel interpenetration framework containing a rotaxane-like motif and 3 is a 2D 44 gridlike layer. Compound 4 contains two kinds of 2D chiral layers composed of three types of single-helical chains and two types of double-stranded helices. Two high-dimensional complexes (3D) with a microporous network containing a 1D metal–organic nanotube filled with plenty of free water molecules for 1, and a 3-fold interpenetrating network with (46·64) topology by considering the cadmium dimer unit as a five-connected node for 5, are observed. Solid-state properties of thermal stability, X-ray powder diffractions, and the photoluminescence properties at room temperature for these crystalline materials have been investigated.以6,6'-二硫二烟酸（H₂cpds，6,6′-dithiodinicotinic acid）的柔性二硫代衍生物为配体，结合两种棒状双氮供体配体：1,2-双(4-吡啶基)乙烷（bpa，1,2-bi(4-pyridyl)ethane）与1,3-双(4-吡啶基)丙烷（bpp，1,3-bis(4-pyridyl)propane），通过液相扩散法成功合成了5种新型锌(II)/镉(II)基配位聚合物1~5，产物经元素分析、红外光谱及X射线衍射进行了表征，其分子式分别为{[Zn(cpds)]·H₂O}ₙ（1）、{[Zn(cpds)(bpa)₀.₅]}ₙ（2）、{[Zn(cpds)(bpp)]}ₙ（3）、{[Cd(cpds)(bpa)₁.₅]·H₂O}ₙ（4）与{[Cd₂(cpds)₂(bpp)·(H₂O)₃]·4H₂O}ₙ（5）。由于H₂cpds配体的不同构象与配位模式，配合物1~5展现出多样的配位基元；同时辅助配体的结构差异在扩展超分子网络的构建中发挥了重要作用。其中配合物2~4均呈现二维层状结构：配合物2拥有含类轮烷基元的二重二维→二维平行互穿骨架，配合物3为二维4⁴网格层状结构；配合物4则包含两类由三种单螺旋链与两种双链螺旋构成的二维手性层。配合物1与5为高维（三维）结构：配合物1拥有微孔网络，其内含有填充大量游离水分子的一维金属有机纳米管；配合物5则以镉二聚体作为五连接节点，构建出具有(4⁶·6⁴)拓扑结构的三重互穿网络。本研究还对上述晶体材料的固态热稳定性、X射线粉末衍射性能以及室温下的光致发光性能进行了表征与探究。