Series of Highly Stable Lanthanide-Organic Frameworks Constructed by a Bifunctional Linker: Synthesis, Crystal Structures, and Magnetic and Luminescence Properties

摘要

By utilizing a preselected functional ligand produced by 1H-imidazole-4,5-dicarboxylic acid, three isostructural lanthanide coordination polymers (CPs), denoted as {[Ln(2)(OH)(2)(L)(2)].(DMF)-(H2O)(4)}n (Ln = Gd (1), Eu (2), Dy (3); L = 1(4-carboxybenzyl)imidazole-4-carboxylic acid), containing a 1D infinite [Ln(4)(OH)(4)] subchain have been successfully constructed. The highly connected mode between the multifunctional ligand and 1D building units is responsible for the exceptional chemical stability of three lanthanide CPs. In addition, a study of the magnetic properties reveals that 1 displays a large magnetic entropy change (-Delta S-m = 30.33 J kg(-1) K-1 with T = 2 K and Delta H = 7 T). Furthermore, genetic algorithm and quantum Monte Carlo methods were combined to simulate the magnetic coupling parameters of compound 1, shedding light on the effect of linking bridges on magnetic propagation. 2 shows intense luminescence in the range of 350-710 nm. Comparably, magnetic studies of 3 reveal the existence of a metamagnetic transformation from an antiferromagnetic interaction to a ferromagnetic interaction along with a decrease in temperature. Through fitting of the results of HF-EPR measurements, a component of the g tensor is obtained, g(II) = 16.4(5), indicating the large anisotropy of 3.