Synthesis and Physicochemical Properties of Terbium(III) and Gadolinium(III) Coordination Compounds with Some Alkyloxybenzoic Acids

New coordination compounds of terbium(III) and gadolinium(III) with alkoxybenzoic acids and 1,10-phenanthroline were prepared by the electrochemical synthesis method. The structure and some properties of the compounds synthesized were studied by IR spectroscopy and luminescence spectroscopy, as well as by thermogravimetry. Mixed-ligand complexes of terbium(III) were found to be thermally stable up to 250–300°C, which enables their deposition by thermal vacuum evaporation in the production of electroluminescent devices. The triplet energy levels of the ligands were determined, and the influence of the neutral ligand on the luminescent properties of the terbium(III) coordination compounds was evaluated.