Lanthanide-pyridyl-2,5-dicarboxylate N-oxide frameworks with rutile topology

Abstract

Four novel lanthanide-organic frameworks Ln(2,5-pdco)(CH₃COO)(H₂O) [Ln = La (1), Eu (2), Gd (3), Tb (4); 2,5-H₂pdco = pyridyl-2,5-dicarboxylic acid N-oxide] have been synthesized and characterized. The coordination networks are similarly constructed viaLn₂(μ-CH₃COO)₂ dinuclear secondary building units (SBUs), which are further linked by six 3-connected 2,5-pdco tectons to result in a novel 3D (3,6)-connected framework with rutile topology. Compound 2 shows the characteristic red emissions of Eu³⁺ at room temperature with the life time of 0.42(1) ms and emission quantum yield of 32.1%. The variable-temperature magnetic susceptibility studies indicate the presence of weak antiferromagnetic coupling between Gd³⁺ in 3 while weak ferromagnetic like one between Tb³⁺ in 4 through chelating-bridging acetate anions, despite their similar crystal structures.