Photophysical and Optical Properties of β-keto Carboxylate Tb(III) Complexes with Heterocyclic Sensitizers

Octa-coordinated terbium complexes containing β-ketocarboxylic acid (L) as main ligand and 1,10-phenanthroline, neocuproine, 2,2-bipyridyl and 2,2-biquinoline as auxiliary ligands have been extensively explored for their optical and photoluminescent properties. Spectroscopic investigations IR and NMR verify that Tb(III) binds to ligand with O-atom and the auxiliary moiety through N-atom. XRD data reveal sharp peaks, indicating the crystalline nature of complexes. The photoluminescence emission spectra for all complexes exhibit a distinct peak at 546 nm, attributed to the ⁵D₄→⁷F₅ transition, which is responsible for green luminescence on exposure to UV light. Additionally, Commission Internationale de l'Éclairage (CIE) color coordinates indicate that synthesized complexes exhibit a green luminous nature. All complexes demonstrated good color purity values. Green luminescence and high thermal stability (210 ℃) of these complexes could be beneficial for developing effective light conversion devices for display and lighting systems. The J-O parameter (Ω₂, Ω₄, Ω₆) and intensity ratio were also calculated to ascertain the coordination environment around the metal ion. Furthermore, we explored the potential application of these complexes in forensic science for latent fingerprint detection, demonstrating their efficacy as enhanced labeling agents. This study establishes a foundation for further research into the utilization of lanthanide complexes in optical applications and forensic investigations.