Structural and Functional Studies of Rare-Earth Complexes With 4-Methylbenzoic Acid and Terpyridine Ligands

This study successfully synthesized four rare-earth complexes (Tb, Er, Ho, and Nd) using 4-methylbenzoic acid (4-MHBA) and 2,2′:6′,2″-terpyridine (terpy) as ligands. Single-crystal X-ray diffraction analysis revealed that all four complexes possess identical binuclear structural features, with crystallographic data confirming their highly consistent space groups and coordination configurations. Structural purity and isostructural characteristics were further verified through complementary characterization techniques including infrared spectroscopy (IR), Raman spectroscopy, and powder X-ray diffraction (PXRD). In this work, thermogravimetric-differential scanning calorimetric technique (TG-DTG-DSC) in combination with its Fourier transformation infrared spectrometry/mass spectrum (FTIR/MS) was used to examine the thermal degradation behaviors of the complexes in a systematic manner. Results demonstrate that the complexes undergo multistage decomposition upon heating, accompanied by the release of characteristic gaseous products. Special emphasis was placed on investigating the luminescent properties of the Tb complex. Under UV excitation, this complex exhibited distinct Tb³⁺ characteristic emission peak wavelengths of 490 and 545 nm, as well as 585 and 620 nm, primarily resulting from the ligand-sensitized “antenna effect.” Fluorescence lifetime confirmed the excellent luminescent performance of this complex.