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(mu 4-tpta)(phen)2(H2O)4] n <middle dot>6nH2O (1) [Co2(mu 4-tpta)(bipy)2(H2O)4] n <middle dot>8nH2O (2), [Ni2(mu 4-tpta)(bipy)2(H2O)4] n <middle dot>7nH2O (3), [Ni2(mu 6-tpta)(py)3(mu-H2O)(H2O)] n <middle dot>2nH2O (4), [Cd2(mu 6-tpta)(mu-bpb)] n <middle dot>nH2O (5), [M2(mu 6-tpta)(mu-dpe)2] n <middle dot>3nH2O [M = Co (6), Mn (7)], and [Co2(mu 6-tpta)(mu-bpa)2] n <middle dot>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.