Synthesis of a functionalized europium complex and deposition of luminescent Langmuir–Blodgett (LB) films

Abstract

The synthesis, characterization and formation of Langmuir–Blodgett (LB) films for the luminescent [(C₁₂H₂₅)₂(CH₃)₂N][Eu(tta)₄] complex, where [(C₁₂H₂₅)₂(CH₃)₂]N⁺ is didodecyldimethylammonium and the tta ligand is thenoyltrifluoroacetone, are reported. The coordination of tta ligands to the Eu³⁺ ion was confirmed by FTIR spectroscopy and the emission spectrum comprised bands corresponding to ⁵D₀ → ⁷F_0–4 transitions. The lifetime (τ) from the emission state (⁵D₀) was 0.41 ms, measured by monitoring the hypersensitive ⁵D₀ → ⁷F₂ transition, with the curve being fitted with a first-order exponential function. The surface pressure–area isotherm indicated that the anionic complex may form condensed structures at the air–water interface due to the amphiphilic properties of the counter ion and the β-diketone ligand. Y-type LB films of [(C₁₂H₂₅)₂(CH₃)₂N][Eu(tta)₄] were deposited on quartz substrates, with preserved luminescence and a band assigned to the ⁵D₀ → ⁷F₂ transition. The molecular arrangement at the air/water interface and the preserved luminescence in LB films are consistent with theoretical predictions using a semi-empirical Sparkle/AM1 calculation method for the molecule in vacuum. These tools were used for the first time to predict the behavior of organized films.