Syntheses, structures, and photoluminescence of lanthanide coordination polymers with pyridine-2,3,5,6-tetracarboxylic acid

Six lanthanide(III) coordination polymers with the formulae {[Ln(Hpdtc)(H2O)(3)]center dot H2O}(n) [Ln = La (1), Ce (2), Pr (3)], {[Ln(Hpdtc)(H2O)(2)]center dot 2H(2)O}(n) [Ln = Eu (4), Tb (5)] and {SmK(pdtc)(H2O)(4)} n (6) (H(4)pdtc = pyridine-2,3,5,6-tetracarboxylic acid) have been synthesized by reacting the corresponding rare earth salts or oxides with H(4)pdtc under hydrothermal conditions. In the three kinds of structure, H(4)pdtc displays three different coordination modes. H(4)pdtc is an elegant ligand with rich coordination sites and low symmetry, but has seldom been used to synthesize complexes. 1-6 are the first examples from lanthanide ions and H(4)pdtc. Furthermore, the novel wave-like T3(2)4(2)6(2) water tape with (H2O)(4) as the substructure is present in complex 6. The two complexes of Eu(III) and Tb(III) exhibit the corresponding characteristic luminescence.