Sculpting Energy Transfer Pathways in Lanthanide Complexes via Fluorinated β‐Diketonate and Substituted Bipyridine Ligands: Experimental and DFT Insights

ABSTRACT

Lanthanide luminescence underpins many modern technologies from chemical sensing and bioimaging to optoelectronic and photonic devices. Among them, europium(III) and terbium(III) complexes are particularly attractive as they efficiently convert UV light into sharp red and green emissions, respectively. Improving their quantum yield is the key to enhancing device sensitivity and performance. Herein, a new heteroleptic series of [Ln(ftfa) ₃ (dmbpy)] complexes (Ln = Eu, Tb, Gd; ftfa = 2‐furoyltrifluoroacetylacetone; dmbpy = 4,4′‐dimethyl‐2,2′‐bipyridine) was synthesized for optimized ligand‐to‐metal energy transfer. The comprehensive structural and spectroscopic characterization (FT‐IR, CHN, HR‐MS, NMR, PXRD, TGA) confirmed their stability and purity. The photophysical investigations, such as including lifetimes, radiative and non‐radiative rate constants, and Judd–Ofelt analysis highlight tunable emissive behavior in solid and solution state. The [Eu(ftfa) ₃ (dmbpy)] exhibits sharp red emission with the experimental total photoluminescence quantum yield of 42%, while the Tb(III) analogue produces characteristic green emission with a yield of 12%. The enhanced efficiency arises from effective ligand‐to‐metal energy transfer processes. The complementary DFT and advanced bonding analyses, like NBO, EDA‐ETS‐NOCV, and LF‐DFT supported these observations, demonstrating strong coordination and favorable thermodynamics. These findings position [Ln(ftfa) ₃ (dmbpy)] complexes as promising candidates for advanced optical applications, including luminescent sensors, imaging probes, and light‐emitting devices.