Wang Xing-Po, Chen Wen-Miao, Qi Hao, Li Xiao-Yi, Rajnák Cyril, Feng Zhen-Yu, Kurmoo Mohamedally, Boča Roman, Jia Chun-Jiang, Tung Chen-Ho, Sun Di
Key Lab of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, P. R. China.
Department of Chemistry, FPV, University of Ss. Cyril and Methodius, 917 01, Trnava, Slovakia.
Chemistry. 2017 Jun 12;23(33):7990-7996. doi: 10.1002/chem.201700474. Epub 2017 Apr 20.
An unprecedented reversible dynamic transformation is reported in a metal-organic framework involving bond formation, which is accompanied by two important structural changes; achiral to chiral and two- to three-dimensions. Using two bent organic ligands (diimpym=4,6-di(1H-imidazol-1-yl)pyrimidine; H npta=5-nitroisophthalic acid) and Co (NO ) ⋅6 H O the coordination polymer Co(diimpym)(npta)⋅CH OH, (1⋅CH OH), was obtained solvothermally. Its structure consists of knitted pairs of square layers (4 -sql net) of five-coordinated Co and disordered methanol, and it crystallized in the achiral Pbca space group at room temperature. It undergoes a single crystal to single crystal (SC-SC) transformation to a 3D interpenetrated framework (α-polonium-type net, pcu) of six-coordinated Co and ordered methanol in the chiral P2 2 2 space group below 220 K. Most unusual is the dynamic temperature-dependent shortening of a Co⋅⋅⋅O connection from a non-bonded 2.640 Å (298 K) to a bonded 2.347 Å distance (100 K) transforming the square pyramidal cobalt polyhedron to a distorted octahedron. The desolvated crystals (1) obtained at 480 K retain the full crystallinity and crystallize in the achiral Pbca space group between 100 and 298 K but the dynamic shortening of the Co⋅⋅⋅O distance connecting the layers into the 3D pcu framework structure is observed. Following post-synthetic insertion of ethanol (1⋅CH CH OH) it does not exhibit the transformation and retains the knitted 2D achiral Pbca structure for all temperatures (100-298 K) and the ethanol is always disordered. The structural analyses thus conclude that the ordering of the methanol induces the chirality while the available space controls the dynamic motion of the knitted 2D networks into the 3D interpenetrated framework. Consequently, 1 selectively adsorbs CO to N and exhibits Type-III isotherms indicating dynamic motion of the 2D networks to accommodate the CO at 273 and 298 K in contrast to the rigidity of the 3D framework at 77 K preventing N from penetrating the solid. The magnetic properties are also reported.
据报道，在一种金属有机框架中发生了前所未有的可逆动态转变，涉及键的形成，同时伴随着两个重要的结构变化：从非手性到手性以及从二维到三维。使用两个弯曲的有机配体（二咪唑嘧啶 = 4,6 - 二（1H - 咪唑 - 1 - 基）嘧啶；5 - 硝基间苯二甲酸）和硝酸钴六水合物，通过溶剂热法得到了配位聚合物Co（二咪唑嘧啶）（5 - 硝基间苯二甲酸）·CH₃OH，（1·CH₃OH）。其结构由五配位钴和无序甲醇的方形层（4 - sql网）的编织对组成，在室温下以非手性的Pbca空间群结晶。在220 K以下，它经历单晶到单晶（SC - SC）转变，成为六配位钴和有序甲醇的三维互穿框架（α - 钋型网，pcu），处于手性的P2₁2₁2空间群。最不寻常的是，一个Co···O连接的动态温度依赖性缩短，从非键合的2.640 Å（298 K）到键合的2.347 Å距离（100 K），将方形金字塔形钴多面体转变为扭曲的八面体。在480 K下获得的去溶剂化晶体（1）在100至298 K之间保持完全结晶性，并以非手性的Pbca空间群结晶，但观察到连接层进入三维pcu框架结构的Co···O距离的动态缩短。在合成后插入乙醇（1·CH₃CH₂OH）后，它不表现出转变，并且在所有温度（100 - 298 K）下都保持编织的二维非手性Pbca结构，乙醇始终无序。因此，结构分析得出结论，甲醇的有序排列诱导了手性，而可用空间控制了编织的二维网络向三维互穿框架的动态运动。因此，1对CO与N₂具有选择性吸附，表现出III型等温线，表明二维网络在273和298 K下具有动态运动以容纳CO，而在77 K下三维框架的刚性阻止N₂穿透固体。还报道了其磁性。
