Co(II), Ni(II), Mn(II), and Cd(II) Coordination Polymers Constructed with Tetracarboxylic Linker: Syntheses, Structural Investigations, and Catalytic Application

Eight transition metal coordination polymers were synthesized via hydrothermal methods utilizing primary ligand [1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta) alongside auxiliary ligands including phenanthroline (phen), 2,2′-bipyridine (bipy), pyridine (py), 1,4-bis(pyrid-4-yl)benzene (bpb), 1,2-di(4-pyridyl)ethylene (dpe), and bis(4-pyridyl)amine (bpa). The synthesis yielded three 1D and five 3D coordination polymers, which were formulated as [Ni2(μ4-tpta)(phen)2(H2O)4]n·6nH2O (1) [Co2(μ4-tpta)(bipy)2(H2O)4]n·8nH2O (2), [Ni2(μ4-tpta)(bipy)2(H2O)4]n·7nH2O (3), [Ni2(μ6-tpta)(py)3(μ-H2O)(H2O)]n·2nH2O (4), [Cd2(μ6-tpta)(μ-bpb)]n·nH2O (5), [M2(μ6-tpta)(μ-dpe)2]n·3nH2O [M = Co (6), Mn (7)], and [Co2(μ6-tpta)(μ-bpa)2]n·2nH2O (8). These coordination polymers were meticulously analyzed using standard methodologies to investigate their topological structures and catalytic properties. Remarkably, Co(II) coordination polymer 8 demonstrated remarkable activity in the Henry reaction with benzaldehydes, attaining elevated yields under optimal conditions. Moreover, it demonstrated remarkable stability, high efficiency, and excellent reusability as a heterogeneous catalyst. This work explores the application of H4tpta as the flexible tetracarboxylate linker for the synthesis of functional coordination polymers.