A 2D + 2D → 3D inclined polycatenated dynamic metal-organic framework of {[Cu(4-bpe)(2-ntp)(HO)]·2HO} [1, where 2-ntp = 2-nitroterephthalate and 4-bpe = 1,2-bis-(4-pyridyl)ethane] has been synthesized and characterized. The variable-temperature powder X-ray diffraction study indicates the dynamic nature of the inclined polycatenated framework, and the dehydrated framework with exposed metal centers exhibits excellent type I H adsorption of 1.94 wt % at 77 K and 1 bar of pressure.
Ap air of supramolecular isomers of Cd II -based MOF have been synthesized by utilizingaflexible N,N'-donor linker and ad icarboxylatew ith ESIPT (excited-state intramolecular proton transfer) fluorophore by varyingt he reaction media.O ne of the MOFs hasa3D four-fold interpenetrating framework with guests olventi nt he structure that undergoes as olvent-dependent crystalline-to-crystalline structural transformation, which has been extensively studied by powderX RD and IR spectroscopy.T he other MOF is structurally rigid in nature and has at wo-fold interpenetrating structure withouta ny guest molecules. Both the compounds show moderate CO 2 adsorption and one of them, the MOF with the four-fold interpenetrating structure, also shows moderately high H 2 adsorption.F urthermore, both the compounds show interesting luminescence behavior.I nt he solid state,t he two compounds show single-peak spectra,w hereas upon suspension of thesec ompounds in polar solvents, the maxima split into two peaks with al arge Stokes shift. On the other hand, in nonpolars olvents, only one emission maximumi so bserved. This solvatochromicd ual-emission phenomenon is due to ESIPT,w hich has been extensively studied.
Three different N,N′-donor ligands with Zn(NO 3 ) 2 •6H 2 O and two different dicarboxylates, flexible succinate (suc) and rigid fumarate (fum) afforded six different metal−organic frameworks (MOFs). Among the N,N′-donor ligands, one bent 1,4-bisHere, 3 is a pillared layer structure, whereas 4 has a 5-fold interpenetrated dimondoid network. For both the bent and straight N,N′-donor ligands an imine alike motif is embedded in the structure. When this motif is replaced by a C−C double bond by using the ligand 1,2-bis(4-pyridyl)ethylene (bpee), it produces two MOFs, {[Zn(bpee 6), having a similar structural relation like 3 and 4 respectively, 5 with a pillared layer structure and 6 with a 5-fold interpenetrated diamondoid network. All the compounds have been thoroughly characterized by powder X-ray diffraction (PXRD), elemental analysis, infrared (IR) spectroscopy, UV−vis spectroscopy, and thermogravimetric analyses. Gas/solvent vapor sorption studies have been carried out for compounds 3−6, which have 3D structures. In the case of 3, an interesting reversible crystalline to crystalline transformation was observed which has been thoroughly studied by PXRD analysis, IR spectroscopy, and UV−vis spectroscopy. Solid state emission spectral analysis for all the complexes was performed at room temperature.
The broad applicability of the hitherto unexplored reagent combination PPh3·HBr-DMSO is exemplified with multiple highly diverse one-step transformations to synthetically useful building blocks, such as flavones, 4H-thiochromen-4-ones, α-hydroxy ketones, 1,4-naphthoquinones (including vitamin K3), 2-bromo-3-substituted-1H-1-indenones, 2-methylthio-1H-1-indenones, 3-butyne-1,2-dione, and 4-pentene-2,3-diones. The simple and mild reaction conditions make the reagent superior in terms of yield and substrate scope in comparison with the existing alternatives.
Interpenetration or catenation is well explored in the network structure of metal organic frameworks, but these kinds of networks were considered as not usable for normal applications of conventional open metal−organic frameworks (MOFs). Recently, flexibility in such networks was found to be an important factor to introduce functionality in the structures of MOFs, and also, the understanding of the factors that control interpenetration also become important. To date, there is no obvious root that has been found to have an interpenetrated network with successive flexibility. In search of such types of networks and to explore the avenue of understanding of growing interpenetration in a framework, six new metal−organic frameworks (MOFs) of Cu(II), Cd(II), and Zn(II) have been synthesized from three flexible dicarboxylates and two rigid dicarboxylates along with 2-methyl-1-(4-(2-methyl-1H-imidazole-1-yl)butyl)-1H-imidazole, as a coligand. All of these synthesized complexes have been characterized by single crystal and powder X-ray diffraction and were further characterized by elemental analysis, infrared spectroscopy (IR), and thermogravimetric analysis (TGA). N 2 , CO 2 , H 2 , and CH 4 sorption studies were also done for all the MOFs, and the characteristic surface adsorptions were found in all cases. Here, from the studies of all these complexes, a common observation is found: flexible dicarboxylates give a noninterpenetrated framework whereas rigid linkers give an interpenetrated framework.
Two coordination polymers (CPs) with a different framework entanglement, namely, a triply interpenetrated two-dimensional (2D) sheet of {[Zn(bpe)(pim)]•(bpe) 0.5 (H 2 O) 3 } n (1) and a doubly interpenetrated three-dimensional (3D) net of {[Cd(bpy)(nbdc)]• (solvent) x } n (2) [where, bpe = 4,4′-bispyridylethane, bpy = 4,4′-bipyridine, pim 2− = dianion of pimelate salt, and nbdc 2− = 2-nitro-1,4-benzenedicarboxylate] were synthesized at room temperature using d 10 metal ions (Zn(II)/Cd(II)) along with two 4-dipyridyl linkers with a variation from flexible aliphatic dicarboxylates to rigid aromatic dicarboxylates. Notably, compound 1 exhibits structural dynamism through reversible solid state SC−SC structural transformation from a 3-fold interpenetrated 2D + 2D → 2D sheet to an interesting higher dimensional 2D + 2D → 3D parallel polycatenated framework (1a). This structural change occurred by heating followed by solvent exclusion. In contrast to 1, compound 2 exhibits a reversible single-crystal-to-single-crystal (SC−SC) structural transformation via the formation of a robust dehydrated framework of 2 (i.e., 2a). These structural transformations are thoroughly studied by powder X-ray diffraction analysis and infrared spectroscopy along with the single crystal X-ray diffraction. All of these structures exhibit a high degree of thermal stability as visualized by thermogravimetric analysis. The dehydrated frameworks of both the compounds were implemented for gas and vapor sorption studies.
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