Structural, thermal, and spectral investigations of the lanthanide(III) biphenyl-4,4′-dicarboxylates

The lanthanide biphenyl-4,4'-dicarboxylates (bpdc) series of the general formulae Ln(2)(bpdc)(3)center dot nH(2)O, where Ln = lanthanides from La(III) to Lu(III); bpdc = C12H5(COO) (2) (2-) ; n = 4, 5 or 6 have been obtained by the conventional precipitation method. All prepared complexes were characterized by elemental analysis, simultaneous thermal analyses thermogravimetric-differential scanning calorimetry (TG-DSC) and TG-FT-IR, FT-IR, and FT-Raman spectroscopy as well as X-ray diffraction patterns measurements. In the whole series of analyzed complexes the bpdc(2-) ligand is completely deprotonated. In view of that, four carboxylate oxygen atoms are engaged in the coordination of Ln(III) ions. The synthesized compounds are polycrystalline and insoluble in water. They crystallize in the low symmetry crystal systems, like monoclinic and triclinic. Heating in the air atmosphere resulted in the multi-steps decomposition process, namely endothermic dehydration and strong exothermic decomposition processes. The dehydration process leads to the formation of stable anhydrous Ln(2)bpdc(3) compounds which subsequently decompose to the corresponding lanthanide oxides.