The effects of the coordination orientation and steric hindrance of ligands on the structural diversity of Pb(II) coordination polymers

Five new lead(II) coordination polymers, [Pb(L)]n (1), [Pb3(L)3]n·4nH2O (2), [Pb2(L)(1,2-bdc)]n·nH2O (3), [Pb2(L)(1,3-bdc)]n·nH2O (4) and [Pb4(L)2(1,4-bdc)2(H2O)2]n·2nH2O (5) (H2L = 4′-(4-carboxyphenyl)-6′-carboxycalte-2,2′-bipyridine, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid, H2(1,3-bdc) = benzene-1,3-dicarboxylic acid and H2(1,4-bdc) = benzene-1,4-dicarboxylic acid) were prepared under hydrothermal conditions. Compound 1 shows a 2D ladder single-layer with the hcb topology. Compound 2 presents a 2D ladder double-layer, which shows a 3-connected hcb topology. Compound 3 exhibits a 1D loop chain based on [Pb4(COO)6] tetranuclear units. Compound 4 displays a (3,4)-connected 3D framework with 3,4T10 topology consisting of [Pb2O2] units. Compound 5 exhibits a self-penetrating 3D network based on [Pb4(COO)2] units, which features an intriguing new topological net. The structural diversity of 1–5 gives some insights that the pH value and coordination orientations of aromatic dicarboxylates play significant roles in construction of coordination polymers. Meanwhile, the hemi-directed or holo-directed coordination geometries depend on coordination numbers of Pb(II) ions. Furthermore, tetrel bonds enhance the structural stability of these Pb(II) coordination polymers. © 2020 Elsevier B.V.