Some properties of Nd and Er complexes with 1,2,3,4,5,6-benzenehexacarboxylic (mellitic) acid

The influence of synthesis conditions on the structural and thermal properties of solid lanthanide 1,2,3,4,5,6-benzenehexacarboxylates (mellitates) was investigated. The general formula of the complexes is Ln2(C12O12)·nH2O (where Ln = Nd(III) and Er(III), n = 10 for Nd, and n = 14 for Er – mild conditions; n = 6 for Nd and Er – hydrothermal synthesis). They were characterized by elemental analysis, X-ray diffraction methods, IR spectroscopy and thermal analysis methods (TG-DSC and TG-FTIR). The prepared complexes are crystalline but not isostructural. The IR spectra confirm deprotonation of all carboxylic groups in all investigated complexes. Their thermal stability as well as pathway of thermal decomposition differ significantly.

► Isostructurality of Nd(3) and Er(4) do not provide the same way of dehydration process.
► Two water molecules of Er(2) were released in the relatively high temperature range.
► FTIR spectra of the gas phase products indicate the release molecules of water, carbon dioxide and carbon oxide.