Abstract
Solvothermal reactions of lanthanide (III) salts with 1,2-phenylenediacetic acid in N,N′-dimethylformamide (DMF) solvent lead to the formation of the metal complexes of the general formula Ln2(1,2-pda)3(DMF)2, where Ln(III) = Pr(1), Sm(2), Eu(3), Tb(4), Dy(5), and Er(6), 1,2-pda = [C6H4(CH2COO)2]2−. The compounds were characterized by elemental analysis, powder and single-crystal X-ray diffraction methods, thermal analysis methods (TG-DSC and TG-FTIR), infrared and luminescence spectroscopy. They exhibit structural similarity in the two groups (Pr, Sm, and Eu; Tb, Dy, and Er), which was reflected in their thermal behaviours and spectroscopic properties. Single-crystal X-ray diffraction studies reveal that Sm(2) and Eu(3) complexes form 2D coordination polymers with four crystallographically independent metal centers. Every second lanthanide ion is additionally coordinated by two DMF molecules. The 1,2-phenylenediacetate linker shows different denticity being: penta- and hexadentate while carboxylate groups exhibit bidentate-bridging, bidentate-chelating, and three-dentate bridging-chelating modes. The infrared spectra reflect divergence between these two groups of complexes. The complexes of lighter lanthanides contain in the structure coordinated DMF molecules, while in the structures of heavier complexes, DMF molecules appear in the inner and outer coordination sphere. Both carboxylate groups are deprotonated and engaged in the coordination of metal centers but in different ways in such groups of complexes. In the groups, the thermal decomposition of the isostructural complexes occurs similarly. Pyrolysis of complexes takes place with the formation of such gaseous products as DMF, carbon oxides, ortho-xylene, ethers, water, carboxylic acids, and esters. The complexes of Eu and Tb exhibit characteristic luminescence in the VIS region, while the erbium complex emits NIR wavelength.
Highlights
As an important branch in the field of supramolecular chemistry and crystal engineering, the design and assembly of metal–organic coordination frameworks (MOFs) or coordination polymers (CPs) have stimulated the interest of chemists over the past few decades [1,2,3,4,5,6,7], due to their intriguing network topologies, and the possible 4.0/).their unpredicted structures
Some coordination polymers based on 1,2-phenylenediacetic ligand, often together with another rigid ligand, have been reported with transition metal ions [19,20,21,22,23,24]
All compounds were obtained in the form of polycrystalline powdered samples but in the case of Sm and Eu complexes, we have been able to isolate in the N,N’-dimethylformamide solution.X-ray
Summary
As an important branch in the field of supramolecular chemistry and crystal engineering, the design and assembly of metal–organic coordination frameworks (MOFs) or coordination polymers (CPs) have stimulated the interest of chemists over the past few decades [1,2,3,4,5,6,7], due to their intriguing network topologies, and the possible 4.0/).their unpredicted structures. As an important branch in the field of supramolecular chemistry and crystal engineering, the design and assembly of metal–organic coordination frameworks (MOFs) or coordination polymers (CPs) have stimulated the interest of chemists over the past few decades [1,2,3,4,5,6,7], due to their intriguing network topologies, and the possible 4.0/). The 1,2-phenylenediacetic acid (1,2-H2pda) has flexible –CH2– groups that cut conjugation and allow free rotation of the carboxylate groups (Figure 1). This dicarboxylic acid bears two C atoms in the aliphatic. Some coordination polymers based on 1,2-phenylenediacetic ligand, often together with another rigid ligand, have been reported with transition metal ions [19,20,21,22,23,24]
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