Mixed-ligand terbium terephthalates: Synthesis, photophysical and thermal properties and use for luminescent terbium terephthalate thin film deposition

Addition of potassium terephthalate K2tph to an aqueous solution of a mixture of terbium nitrate and ancillary ligands L resulted in the formation of mixed-ligand terbium terephthalates Tb2tph3(TPPO)8(H2O)4 (II), Tb2tph3(TOPO)2(H2O)4 (III), Tb2tph3(diglyme)2(H2O) (IV), Tb2tph3(tetraglyme)4(H2O)3 (V), Tb2tph3(Phen)2(H2O)2 (VI). The composition of the mixed-ligand complexes (MLCs) was confirmed by elemental analysis, Raman spectroscopy, thermal analysis, and luminescent spectroscopy. According to the thermal analysis data, II–V exhibit lower thermal stability in comparison with the terephthalate hydrate Tb2tph3(H2O)4 (I). MLCs II, IV, and V are able to eliminate ancillary ligands, followed by formation of anhydrous Tb2tph3, while in case of III and IV ligand elimination is accompanied by partial thermal decomposition of Tb2tph3. Solubility tests showed that MLC II exhibits sufficient solubility in acetonitrile for thin film deposition. Thus thin films of II were deposited by spin-coating, and luminescent thin films of Tb2tph3 were obtained for the first time by thermal treatment of II films.