Synthesis of Metallomacrocycle and Coordination Polymers with Pyridine-Based Amidocarboxylate Ligands and Their Catalytic Activities towards the Henry and Knoevenagel Reactions.

Abstract

The reactions of 3,3′‐{(pyridine‐2,6‐dicarbonyl)bis(azanediyl)}dibenzoic acid (H2L) with zinc(II), cadmium(II), and samarium(III) nitrates were studied, and the obtained compounds, [Zn(1κO:2κO′‐L)(H2O)2]n (1), [Cd(1κO 2:2κO 2‐L)(H2O)2]2 ⋅6n H2O⋅ n C4H8O2 ⋅1.5n DMF (2), and [Sm(1κO:2κO′O′′:3κO′′′‐L)(NO3)(H2O)(dmf)]n ⋅ n DMF (3), were characterized by elemental analysis, FTIR spectroscopy, thermogravimetric analysis, and X‐ray single‐crystal diffraction. Compounds 1 and 3 have 1D zigzag‐ and double‐chain‐type structures, respectively, whereas 2 features a dinuclear metallomacrocyclic complex. The ligand (L2−) orients in different conformations, that is, syn‐syn for 1 and anti‐anti for 2 and 3. Compound 1 is the first example in which the syn‐syn conformation for this ligand has been observed. These compounds act as heterogeneous catalysts for the nitroaldol (Henry; in water medium) and Knoevenagel condensation reactions of different aldehydes, and the most effective is zinc coordination polymer 1. Recyclability, heterogeneity, and size‐selectivity tests were performed, which showed that the catalyst was highly active over at least four recycling runs.