Structures, luminescent and magnetic properties of a series of (3,6)-connected lanthanide–organic frameworks

Abstract

Through hydrothermal reactions with corresponding lanthanide nitrates and 4-(4-carboxyphenylsulfonyloxy)-3-metnoxybenzoic acid (H₂vspc), seven novel three-dimensional (3D) lanthanide–organic frameworks ([Ln(vspc)(Hvspc)(H₂O)]_n [Ln = Pr (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6) and Er (7)]) have been synthesized and structurally characterized. All of them are isostructural and crystallize in the monoclinic crystal system, P2₁/c space group. Their structures feature a (3,6)-connected topological network, in which Ln³⁺ were connected by carboxylate groups to give a 1D lanthanide chain, and the adjacent chains are further spanned by vspc²⁻ and Hvspc⁻ anions to form a 3D framework. The luminescent properties and lifetimes of 2 (Eu^III), 4 (Tb^III), and 5 (Dy^III) have been studied, and the corresponding luminescent lifetimes are 0.53, 0.99 and 0.014 ms, respectively. The magnetic investigations reveal that compound 3 displays weak antiferromagnet interaction, 4 and 5 exhibit ferromagnetic coupling, and compound 5 exhibits slow magnetic relaxation behavior.