Thermal and spectroscopic (IR, XPS) properties of lanthanide(III) benzene-1,3,5-triacetate complexes

Abstract

The metal–organic frameworks of the formula Ln(bta)·nH2O where n = 3, 4, 5 or 6; bta = benzene-1,3,5-triacetate ion: [C9H9(COO)3]3−; Ln = La(III), Nd(III), Eu(III), Tb(III), Ho(III), Tm(III), Lu(III) were synthesized by the reaction of LnCl3·xH2O with ammonium salt of H3bta acid in water solution. Insoluble water compounds crystallize in the monoclinic or triclinic crystal system, and they are stable up to 30 °C. When heated, they decompose up to 160–200 °C in two stages to stable anhydrous compounds. The dehydrated compounds Ln(bta) are still crystalline and stable up to about 350 °C. When heated above 350 °C, they undergo decomposition where the intermediate products are Ln2O2CO3 or Tb4O6CO3 and the residues are: Ln2O3 or Tb4O7. The interpretation of IR spectra of title compounds was made taking into consideration the experimental and theoretical wavenumbers obtained for H3bta specie. The XPS spectra of H3bta and its complexes were recorded. The way of metal–carboxylate group of ligand coordination was discussed. This work presents the results of the XPS analyses, which allowed to determine the binding energies (E b) for the main lines of Ln3d, Ln4d, Ln5p, C1s, O1s spectra, spin–orbital splitting and full width at half maximum complexes.