Series of anion-directed lanthanide-rigid-flexible frameworks: syntheses, structures, luminescence and magnetic properties

A series of novel self-assembly lanthanide coordination polymers formulated as {[Ce-2(pyda)(2)(mu(4)-SO4)center dot 5H(2)O]center dot 2H(2)O}(n) (1), {[Gd-2(Hpimda)(2)(mu(4)-C2O4)center dot 4H(2)O]center dot 2H(2)O}(n) (2), {[Sm-4(pyda)(2)(mu(4)-C2O4)(4)center dot 8H(2)O]center dot 6H(2)O}(n)} (3), and {[Gd-2(pyda)(mu(4)-C2O4)(2)center dot 4H(2)O]center dot 3H(2)O}n (4), (H(3)pimda = 2-propyl-4,5- imidazole-dicarboxylic acid, H(2)pyda - 2,6-pyridine-dicarboxylic acid) have been synthesized from the reactions of H(3)pimda or H(2)pyda with lanthanide salts in the presence of different anions, and were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Compound 1 is a 2D hybrid in which Ce3+ ions are doubly linked by a carboxylate group of the pyda(2-) ligand. Complexes 2, 3 and 4 have 3D framework structures fabricated through two alternately arranging hexanuclear Ln(3+) motifs, among which the guest water molecules are trapped in the 1D tunnel. In 3 and 4, the [Ln(2)(pyda)(2)](n) layers also consist of alternate left- and right helical chains. Both complexes 2 and 4 exhibit the robust network based on the hexadimeric subunits as 3,3-connected nodes. The emission spectra of the complexes vary depending on which lanthanide ion is present and the aromatic ligands. In addition, compound 1 exhibits weak but significant ferromagnetic couplings between the Ce(III) ions through carboxylato bridges, while dominant antiferromagnetic interactions were observed in compounds 2, 3 and 4.