Structural Variation and Preference in Lanthanide-pyridine-2,6-dicarboxylate Coordination Polymers

Abstract

Ten lanthanide coordination polymers were designed and synthesized using pyridine-2,6-dicarboxylic acid (H 2 pdc) and two different heating techniques (conventional and microwave): [Ln(pdc)(H 2 O) 4 ] 3 •3Cl {Pa3̅ ; Ln = Pr (I), Nd (II), Sm (III), Eu (IV), and Gd (V)}, [Ln(pdc)(Hpdc)-(H 2 O) 2 ]•3H 2 O {P2 1 /c; Ln = Pr (VI), Nd (VII), and Sm (VIII)} and [Ln(pdc)(H 2 O) 4 ] 3 •3Cl {Ia3̅ ; Ln = Sm (IX), and Eu (X)}. These complexes show variation in structures depending on the heating technique and the lanthanide ions.They can be classified into the cubic Pa3̅ (I−V) and Ia3̅ (IX, X), and the monoclinic P2 1 /c (VI−VIII) complexes. The cubic complexes exhibit supramolecular isomerism and a tubular three-dimensional structure of interpenetrated lcs and pcu net topologies, while the monoclinic complexes are the supramolecular assemblies of the one-dimensional chains. As the cubic Pa3̅ structures are favored by the use of the microwave, there is variation in structures as conventional heating was employed, although the cubic Pa3̅ structures are still the most favored except for the VI case. The title complexes showed moderate thermal stabilities. The organic ligand is revealed to be a modest sensitizer to initiate the photoluminescence in the title complexes.

Two Novel Lanthanide Metal–Organic Frameworks: Selective Luminescent Sensing for Nitrobenzene, Cu2+, and MnO4–

“…Compound 2 represents the typical luminescence of Eu 3+ ions excited at 351 nm, where four characteristic emissions at 591, 615, 651, and 698 nm originate from 5 D 0 to 7 F J ( J = 1, 2, 3, and 4) transition were observed (Figure S5). Among these transitions, the intensity of the 5 D 0 → 7 F 2 electric dipole transition, which dominates the bright red light, is much stronger than the 5 D 0 → 7 F 1 magnetic dipole transition because of the low symmetry of the Eu­(III) ion. − …”

Crystal structures of two SmIII complexes with dipicolinate [DPA]2− ligands: comparison of luminescent properties of products obtained at different pH values

“…The luminescent characteristics can be explained by the fact that the formed lanthanide(III) complex with three [DPA] 2ligands coordinating to the central lanthanide(III) cation exhibits an almost perfect tricapped trigonal prism (TTP) coordination environment (Albertsson, 1970;Brayshaw et al, 1995;Kim et al, 1998;Li et al, 2019;Murray et al, 1990;Salaam et al, 2022;Zhou et al, 1994). The luminescence properties have been studied in great depth; however, our knowledge of Sm III with [DPA] 2as the ligand is rather limited (Chuasaard et al, 2017;Kumar et al, 2019;Sharif et al, 2016;Viveros-Andrade et al, 2017).…”

Thermodynamic Modeling and Solubility Parameter of 2,6-Pyridinedicarboxylic Acid in Selected Solvents at Different Temperatures

“…Coordination polymers (CPs) with nitrogen-containing heterocyclic ligands attracted a lot of attention during the recent decades because of their unique structures relevant for applications related to fluorescence, catalysis, adsorption, and magnetism . Among various nitrogen-containing heterocyclic compounds, pyridine-dicarboxylic acids are excellent ligands because of their outstanding biological activity and strong coordination ability. − 2,6-Pyridinedicarboxylic acid (PDCA, C 7 H 5 NO 4 , CAS no. 499-83-2) contains two carboxylic groups on each side of the pyridine ring.…”