Syntheses, structures, and luminescent properties of three novel two-dimensional lanthanide coordination polymers with mixed aromatic carboxylate ligands

Three novel two–dimensional (2–D) coordination polymers {[Ln (bpdc) (BDC)0.5 (DMF) (H2O)]·1.5H2O}n [Ln = Tb (1), Sm (2), Gd (3); H2bpdc = 2,4′–biphenyldicarboxylic acid; H2BDC = 1,4–benzenedicarboxylic acid, and DMF = N,N′–dimethylformamide] have been successfully synthesized by the reactions of metal source Ln(NO3)2·5H2O with mixed aromatic carboxylate ligands named, H2bpdc and H2BDC in the mixed solution of DMF and H2O. Complexes 1–3 were characterized by element analyses, IR spectroscopy and single–crystal X–ray diffraction. The results reveal that three complexes are isostructural. In the molecular structure of 1, the neighboring Tb3+ cations are connected by the edge sharing fashion from two three-bridging μ3–oxygen atoms to construct a dinuclear polyhedron. The adjacent dinuclear units are linked by two bpdc2– ligands to form an infinite double zigzag chain containing quadrangular grids. These chains are linked by BDC2–, which acted as pillar to form a 2-D layered structure containing (4, 4) networks. The solid–state luminescent properties of complexes 1 and 2 were investigated at room temperature. Complexes 1 and 2 have displayed their characteristic emissions and decay lifetimes.