Three types of lanthanide coordination polymers from 1D to 3D based on a tetracarboxylate ligand: synthesis, structural diversities and properties

Abstract

Three types of lanthanide coordination polymers with the formulas [Ln(Habtc)(H₂O)(DMA)]_n (1–3) {Ln = Ho (1), Er (2), Tm (3)}, [Ln(Habtc)(H₂O)₂(DMF)]_n (4–6) {Ln = Gd (4), Er (5), Tm (6)} and {[(CH₃)₂NH₂][(H₂abtc)₂Ln(H₂O)]·5H₂O}_n {Ln = Gd (7), Dy (8), Er (9), Tm (10)} were constructed under solvothermal conditions in the presence of 3,3′,5,5′-azobenzenetetracarboxylic acid (H₄abtc). They have three structural types from 3D to 1D polymers. The structural features of the three types of Ln-CPs are as follows: 1–3 shows a three-dimensional (3D) framework with an sni-type topology. Compounds 4–6 form a 2D sheet-like extended structure and these sheets stack on each other to give a 3D supramolecular architecture. The structures of 7–10 can be described as 1D chains constructed from Ln³⁺ ions and H₂abtc²⁻ ligands. The versatile structures well exhibit the rich coordination chemistry of H₄abtc and the coordination geometries of Ln^III ions. In addition, the magnetic and luminescence properties of complex 8 were investigated. Luminescent selective and sensitive sensing of Cr³⁺ compared with other metal ions was investigated by using 8. Moreover, the 1D anionic lanthanide coordination polymer 10 presents highly selective adsorption of cationic dyes via ion-exchange processes. The results show that H₄abtc is a good ligand for constructing CPs with varying structures and properties.