ABSTRACT Strategic ligand design continues to play a critical role in optimizing the photophysical behavior of lanthanide complexes for functional materials applications. In this work, a new series of green‐emitting Tb(III) complexes was synthesized using a chromone‐derived primary ligand, 6‐ethyl‐4‐oxo‐4 H ‐1‐benzopyran‐3‐carboxaldehyde. The coordination environment of the complexes was systematically modulated by introducing various N , N ′‐donor auxiliary ligands, including bathophenanthroline, 1,10‐phenanthroline, and 2,2′‐bipyridine, to enhance their luminescent performance. The complexes were comprehensively characterized by FTIR, CHN, PXRD, UV–vis, PL, and TGA. FTIR, CHN, and UV–vis measurements confirmed complex formation and ligand coordination. Sharp peaks in x‐ray diffractograms suggest their crystalline nature. All complexes exhibited the characteristic sharp 5 D 4 → 7 F J ( J = 6–3) transitions, with emission peaks at approx. 491, 547, 587, and 623 nm corresponding to the dominant green 5 D 4 → 7 F 5 transition. Among these, the bipyridine‐containing complex (Tb4) displayed the highest quantum yield (66.20%) and an extended emission lifetime (0.67 ms), attributed to efficient energy transfer and minimized non‐radiative decay. TGA confirmed good thermal stability, with decomposition temperatures above 200°C. These findings highlight the importance of ligand architecture and coordination geometry in tuning the optical and thermal properties of Tb(III) complexes for advanced photonic and solid‐state lighting technologies.
Langyan et al. (Sun,) studied this question.