Abstract
The new 1D CPs [Zn(L1)(H2O)4]n.nH2O (1) and [Zn(L2)(H2O)2]n (2) [L1 = 1,1′-(ethane-1,2-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid); L2 = 1,1′-(propane-1,3-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid)] were prepared from flexible dicarboxylate pro-ligands (H2L1 and H2L2). Both CPs 1 and 2 were characterized by elemental, FTIR, and powder X-ray diffraction analysis. Their geometry and the structural features were unveiled by single-crystal X-ray diffraction analysis. The underlying topology of the CPs was illustrated by the topological analysis of the H-bonded structure of CP 1, which revealed a 3,4,6-connected trinodal net. On the other hand, topological analysis on the hydrogen-bonded network of CP 2 showed a 2,3,3,4,6,7-connected hexanodal net. The thermal stability of the CPs was investigated by thermogravimetric analysis. CPs 1 and 2 act as heterogeneous catalysts in one-pot tandem deacetalization–Knoevenagel condensation reactions under environmentally mild conditions. CPs 1 exhibits a yield of ca. 91% in a microwave-assisted solvent-free medium, whereas a slightly lower yield was obtained for CP 2 (87%) under the same experimental protocol. The recyclability of catalyst 1 was also assessed. To our knowledge, these are the first Zn(II)-based CPs to be applied as heterogeneous catalysts for the above tandem reactions under environmentally friendly conditions.
Highlights
Coordination polymers (CPs) have attracted an enormous interest over the years because of their intriguing architectures and topologies, and for their diversified applications in various areas such as gas adsorption and separation, molecular magnetism, luminescence, sensing, etc. [1,2,3,4,5,6,7]
It is noteworthy to mention that the present study provides the first report on Zn(II) based CPs, which act as a heterogeneous catalyst for the above tandem reactions in a solvent-free medium
The underlying topology of the CPs was illustrated by the topological analysis of H-bonded structure of CP 1, which revealed a 3,4,6-connected trinodal net and point symbol
Summary
Coordination polymers (CPs) have attracted an enormous interest over the years because of their intriguing architectures and topologies, and for their diversified applications in various areas such as gas adsorption and separation, molecular magnetism, luminescence, sensing, etc. [1,2,3,4,5,6,7]. Apart from these, CPs, as heterogeneous catalysts have marked their foothold due to their recyclability and easy workup [8,9,10,11,12,13] Numerous factors such as the choice of organic ligands, metal ions, solvent, metal to ligand ratio, pH, temperature, etc. Among the different organic linkers, flexible multicarboxylate (in particular dicarboxylate) ligands have been regularly employed as multifunctional linkers in light of their plentiful coordination modes to a metal ion for the generation of polymeric frameworks. MOFs/CPs as catalysts forbarrier such reactions carried ronmentally friendly solvent-free conditions. )(H2O)4]n.nH2O friendly (1) and (2), flexible ligandsand and their as environmentally [Zn(L2)(H2O)2]n catalysts (2), with flexible multicaboxylate ligands and their application as environheterogeneous for solvent-free microwave-assisted one-pot deacetalization–.
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