SYNTHESIS, CHARACTERIZATION AND JUDD-OFELT ANALYSIS OF Eu(III) OR Sm(III) β DIKETONATE COMPLEXES

The lanthanide complexes [Ln(bmdm)₃(L)] where Ln(III) = Eu and Sm were synthesized successfully using the diketone (1-(4-methoxyphenyl)-3-(4-tert-butylphenyl) propane-1,3-dione) (bmdm) and (L) = 1,10-phenanthroline (phen), 2,2’-bipyridine (bipy) ligands. The coordination modes were determined as bidentate chelate by the FT-IR. The ground state geometry was determined using the Sparkle/AM1 implemented in MOPAC2016 package. Europium complexes exhibit the characteristic emission bands that arise from⁵D₀→⁷F_J (J = 0-4); the presence of just one⁵D₀→⁷F₀ line transition means that this site is without the center of inversion. Samarium complexes display transitions at⁴G_5/2→⁶H_J (J = 5/2; 7/2; 9/2 and 11/2), being the⁴G_5/2→⁶H_9/2 the most intense, indicating that the forced electric dipole mechanism is predominant when compared with the magnetic dipole ones. The intensity parameters Ω₂ and Ω₄ were calculated according to the emission spectra for Eu(III) and absorption spectra for Sm(III). The high Ω₂ values demonstrated that the lanthanide ion in bipy or phen complexes is in a highly polarizable chemical environment. The emission lifetime (τ) increases compared with that of precursor aquo complexes, confirming that the non-radiative quenching is minimized. The low quantum efficiency is a result of NIR emissions and non-radiative transitions of Sm(III).

Keywords:
lanthanide β-diketonates; photoluminescence; Sparkle Model; Judd-Ofelt parameters