Lanthanide complexes with pyridinecarboxylic acids - Spectroscopic and thermal studies

The effect of 14 lanthanides on the structure and the electronic system of isonicotinic acid was studied using IR (KBr), IR (ATR), Raman, UV-Vis, spectrofluorometric, elemental analysis and thermogravimetric (TG/DTG) methods. The influence of the lanthanides ions on the electronic charge distribution of the ligand is discussed. The nephelauxetic parameters and the degree of covalency in the lanthanide-ligand bonds were established. Moreover, the molecular structures of the lanthanide complexes with isonicotinic, nicotinic, picolinic and benzoic acids were compared, with a particular emphasis on the changes within the aromatic ring of metal complexes. (C) 2018 Elsevier Ltd. All rights reserved.