Synthesis, structure and properties of 2D lanthanide coordination polymers based on N-heterocyclic arylpolycarboxylate ligands†
Abstract
The reaction of 3-(2,4-dicarboxyphenyl)-2,6-pyridinedicarboxylic acid (H4dppd) with rare earth nitrates under hydrothermal conditions generated a series of new two-dimensional (2D) coordination polymers, namely {[La(Hdppd)(H2O)2·(H2O)2]n (1), [Ln2(Hdppd)2(H2O)4·(H2O)3]n [Ln = Sm (2), Eu (3)] and [Ln(Hdppd)(H2O)3·H2O]n [Ln = Gd (4), Tb (5), Dy (6), Ho (7), Er (8)] [Hdppd = 3-(2,4-dicarboxyphenyl)-2,6-pyridinedicarboxylic trivalent anion]}. The complexes were characterized by X-ray single-crystal diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Luminescence spectroscopy of 3 and 5 showed bright red and green luminescences due to the 4fn–4fn transitions in Eu3+ and Tb3+ respectively, although the luminescence lifetime is shortened by non-radiative decay due to the presence of coordinating water molecules. The magnetic properties of 2–8 were measured and discussed. Compound 6 exhibits frequency dependent out-of-phase signals, and ferromagnetic coupling exists in 8.
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