Supramolecular architecture of new lanthanide coordination polymers of 2-aminoterephthalic acid and 1,10-phenanthroline

This paper presents five new lanthanide coordination polymers with 2-aminoterephthalic acid (H2atpt) and 1,10-phenanthroline (phen), [Ln(atpt)1.5(phen)(H2O)]n [Ln = La (1); Eu (2)], [Ln2(atpt)3(phen)2(H2O)]n [Ln = Tb (3); Er (4)] and [Yb2(OH)(atpt)2.5(phen)2]n·1.75nH2O (5), prepared by hydrothermal reactions and structurally characterized. 1 and 2 are isostructural, in which all the Ln3+ ions are eight-coordinated. 3 and 4 are also isostructural and have two types of lanthanides; Ln(1) (Ln = Tb, Er) is seven-coordinated and Ln(2) (Ln = Tb, Er) is eight-coordinated in the asymmetric unit. 1–4 are two-dimensional rhombus-like grids constructed by bridging atpt ligands, and further form 3-D supramolecular architectures via hydrogen bonds and π–π stacks between phen molecules. Complex 5, in which there are two eight-coordinated Yb3+ ions linked by one hydroxyl group and one atpt ligand in the asymmetric unit, exhibits an interpenetrated 3-D network with a brick structure. In 1–4 one atpt ligand is coordinated to three or four Ln3+ ions (Ln = La, Eu, Tb, Er) in bridging modes and in 5 one atpt ligand is coordinated to two or three Yb3+ ions by double chelating or chelating-bridging mode. The high-resolution emission spectrum of 2 shows only one Eu3+ ion site in 2, which is in agreement with the results of the X-ray diffraction. The thermal stabilities of the supramolecular compounds 2, 4 and 5 show that the presence of amino groups induces formation of hydrogen bonds that are responsible for the increase in the thermal stability.