Polymeric and Dimeric Rare Earth Phenylbutylacetate Complexes: Structural Effects on TR³⁺ Emission Efficiency

Lanthanide coordination compounds are promising materials for photonic applications owing to their unique luminescent properties. Herein, six Eu³⁺, Tb³⁺, and Gd³⁺ complexes with the general formulae [Ln(pba)₃(H₂O)]∞ and [Ln₂(pba)₆(phen)₂] were synthesized and investigated to evaluate the influence of the coordination environment on their photophysical behavior. Structural and spectroscopic characterization was performed by CHN elemental analysis, FTIR, UV–Vis absorption, and luminescence spectroscopy. The Eu³⁺ complexes exhibited markedly different quantum yields depending on the coordinated ligand, increasing from 26% for [Eu(pba)₃(H₂O)]∞ to 63% for [Eu₂(pba)₆(phen)₂] at 300 K. This enhancement is attributed to the replacement of coordinated H₂O by 1,10-phenanthroline, which suppresses non-radiative deactivation pathways and improves ligand-to-metal energy transfer. JOYSpectra calculations further confirmed the decisive role of the coordination environment in governing the luminescence efficiency of these compounds.