Coordination Compounds of Lanthanides with 3-Hydroxy-4-oxo-4H-pyran-2,6-dicarboxylic Acid: Synthesis, Structure, and Photoluminescent Properties

Complex compounds of 3-hydroxy-4-oxo-4H-pyran-2,6-dicarboxylic (meconic) acid (H(3)Mec) with europium(III), gadolinium(III), terbium(III), dysprosium(III), erbium(III), thulium(III) and ytterbium(III) ions were synthesized by the ion exchange method in aqueous solution. The hydrates of the complex compounds [Ln(HMec)(H2O)]center dot nH(2)O (n = 0-4) are solid amorphous substances (Sm3+, Eu3+, Gd3+, and Tm3+ complexes) and fine crystalline substances (Tb3+, Dy3+, Er3+, and Yb3+ complexes) with colors characteristic of lanthanide ions. The region of thermal stability of the complexes was determined by the TG/DTG/DSC methods. The Ln(3+) ions are coordinated monodentately to the ionized carboxyl groups and the oxygen atom O-1 of the pyrone ring. The coordination of Ln(3+) to the C-3-OH group and the C-4=O ketogroup of the second ligand molecule leads to the formation of a polymer chain. The triplet level of the ligand (T-3*) was determined from the phosphorescence spectrum of the Gd3+ complex compound (77 K). The spectral-luminescent properties of Sm3+, Eu3+, Tb3+, Dy3+, and Tm3+ complexes were studied.

Automated summary

Complex compounds of 3-hydroxy-4-oxo-4H-pyran-2,6-dicarboxylic (meconic) acid with europium(III), gadolinium(III), terbium(III), dysprosium(III), erbium(III), thulium(III) and ytterbium(III) ions were synthesized by ion exchange method in aqueous solution. The compounds exhibited different crystalline and thermal stability properties, while lanthanide ions were coordinated to carboxyl groups and oxygen atoms forming polymer chain. The triplet level of the ligand was determined by phosphorescence spectrum of the Gd3+ complex compound, and the luminescent properties of other complexes were studied.