Metal–Organic Frameworks Built from a Linear Rigid Dicarboxylate and Different Colinkers: Trap of the Keto Form of Ethylacetoacetate, Luminescence and Ferroelectric Studies
作者:Tapan K. Pal、Rajesh Katoch、Ashish Garg、Parimal K. Bharadwaj
DOI:10.1021/acs.cgd.5b00784
日期:2015.9.2
The ligand 2,6,2′,6′-tetranitro-biphenyl-4,4′-dicarboxylic acid (H2L) has been used alone or with a coligand to construct a number of metal organic frameworks (MOFs) with different metal ions that are X-ray crystallographically characterized. The porous three-dimensional (3D) MOF [Gd2(L)3(DMF)4]·(4DMF)·(3H2O)}n (1) (DMF = N,N′-dimethylformamide) is found to be an excellent host to the keto form of ethylacetoacetate to produce [Gd(L)1.5(DMF)2(H2O)2](S)(H2O)}n (1a) (S = ethyl 3-oxobutanoate) in single crystal to single crystal (SC–SC) transformation. This involves drastic rearrangement of the channels including several carboxylate shifts and concomitant movement of water molecules from the cavity to the metal center. Interestingly, the daughter framework 1a reverts back to the mother framework 1 upon keeping it in DMF for 3 days at room temperature, suggesting that the framework 1 can be used as a container. The linker H2L also forms the MOFs [(Cd)4(L)3(HlL1)2(DMF)(H2O)2](DMF)3(H2O)2}n (2), [Cd(L)(L2)]}n (3), [(Cd)1.5(L)1.5(L3)]}n (4), and [Cd(L)(L4)(H2O)]}n (5) in the presence of different colinkers. Solid-state photoluminescence studies performed on MOFs 2–5 at room temperature showed intraligand (π–π*) emission. The MOF 2 being a chiral compound has been subjected to ferroelectric measurements. All the compounds (1–5) have been characterized by X-ray crystallography, elemental analysis, powder X-ray diffraction patterns, thermogravimetry, and infrared spectroscopy.
配体2,6,2′,6′-四硝基联苯-4,4′-二羧酸(H2L)单独使用或与共配体合用构筑了多种金属有机骨架(MOFs),其中不同的金属离子经X射线晶体学表征。多孔三维(3D)MOF [Gd2(L)3(DMF)4]·(4DMF)·(3H2O)}n(1)(DMF=N,N′-二甲基甲酰胺)被发现是乙酰乙酸乙酯的酮式结构的优秀的宿主,以单晶到单晶(SC–SC)转化的方式生成[Gd(L)1.5(DMF)2(H2O)2](S)(H2O)}n(1a)(S=乙基-3-氧代丁酸酯)。过程涉及包括若干羧酸盐位移及水分子从腔体到金属中心的伴随运动的通道重组。有趣的是,经过框架1a在室温下于DMF中放置3天,产物的母体框架1会还原回来,说明框架1能够用作容器。配体H2L也形成了MOF [(Cd)4(L)3(HlL1)2(DMF)(H2O)2](DMF)3(H2O)2}n(2)、[Cd(L)(L2)]}n(3)、[(Cd)1.5(L)1.5(L3)]}n(4)、[Cd(L)(L4)(H2O)]}n(5),这些都是在不同共配体存在下形成的。在室温下对MOFs 2~5进行了固体荧光性能的研究,发现有配体内(π–π*)发射。由于MOF 2是一种旋光化合物,所以对其进行了铁电性测定。所有的化合物(1~5)都经X射线晶体学、元素分析、粉末X射线衍射谱图、热重分析和红外光谱进行了表征。