Synthesis and Crystal Structures of a Lanthanum(III) 1D Polymer and a Mixed-Ligand Cerium(III) Binuclear Complex Derived from Pyridine-2,6-dicaboxylic Acid

Abstract

Lanthanum(III) and cerium(III) complexes of pyridine-2,6-dicaboxylic acid (H(2)Pydc) have been prepared and their crystal structures were determined by X-ray crystallography. The single crystal analysis reveals that the lanthanum(III) complex, 1 is polymeric consisting of {[La(Pydc)(2)(H2O)(2)]center dot 4H(2)O} (n) units linked through carboxylate oxygen atoms and exhibiting nine coordination number. Intermolecular O-H center dot center dot center dot O hydrogen bonds produce R (1) (1) (6), R (4) (4) (16) and R (4) (4) (20) rings, which lead to three-dimensional polymeric chains. The crystal structure of the cerium(III) complex, 2 [{Ce(Pydc)(3)}{Ce(Pydc)(HO-CH2CH2-OH)(H2O)(3)}center dot 6H(2)O)] shows that the complex is a mixed-ligand binuclear system in which one cerium coordinated to three Pydc molecules, while the other cerium is bound to one Pydc, one oxygen atom of the other Pydc, one ethylene glycol and three water molecules. Each of the two Ce(III) ions is nine coordinated. Intermolecular O-H center dot center dot center dot O hydrogen bonds produce R (2) (2) (8) and R (2) (2) (20) rings, which lead to three-dimensional polymeric chains. The complexes were further investigated using elemental analysis, FTIR spectroscopy and thermogravimetric analysis.