Structural diversity of lanthanide coordination polymers with 2,2′-biquinoline-4,4′-dicarboxylate

Eight new lanthanide complexes [Ln(bqdc)1.5(phen)] (Ln = La, 1; Pr, 2), [Gd4(bqdc)4(µ3–OH)4(H2O)4]·4H2O (3), [Ln2(bqdc)2(µ3–OH)2(H2O)2]·2H2O (Ln = Tb, 4; Yb, 5), [NaLn(bqdc)1.5(Ac)(H2O)2] (Ln = Pr, 6; Nd, 7; Y, 8) (bqdc2− = 2,2′-biquinoline-4,4′-dicarboxylate, Ac = acetate, phen = 1,10-phenanthroline) have been prepared by hydro/solvothermal reactions and characterized by single-crystal X-ray diffraction. Complexes 1 and 2 are isostructural, and have a 2D layered framework. Complex 3 is built from a tetrahedral tetranuclear gadolinium hydroxo cluster, and possesses a 3D metal–organic framework with a 1D channel along the b-axis. And in 3, there are R- and L- (–M–O–C–O–M–)n helical chains which are formed by a bqdc2− ligand linking the cubane-like building block along the b-axis. Complexes 4 and 5 are isostructural, but they have similar 3D packing to 3, the difference can be found in the cell parameter. Complexes 6–8 are isostructural, and have a 3-D metal–organic framework which is built from parallelogram-like heterotetranuclear unit linked by one oxygen atom of acetate. The magnetic properties of 3, 6 and 7 are investigated.