Red EuropiumIII complexes: Synthesis, photophysics and optoelectronics properties

In this article, four Eu^III complexes of ternary nature, [Eu(bfa)₃(L)_x] {L = diphenyl sulphoxide (dpso) (1), dpsoCl (bis(4-chlorophenyl) sulphoxide) (3) and tppo (triphenylphosphine oxide) (x = 2) (4), and dpsoCH₃ (4,4′-dimethyldiphenylsulfoxide) (x = 3) (2)}, bfa = 4,4,4-Trifluoro-1-phenyl-1,3-butanedione}, were synthesised and thoroughly characterized. The structures of the complexes were confirmed by FTIR, ¹³C and ¹H NMR analyses. The Sparkle model/PM7 analysis shows that the complexes possess structural geometries as: 1 and 4 – Biaugmented trigonal prism, 3 –square antiprism, and 2 –spherical capped square antiprism. The complexes exhibit red luminescence with a photoluminescence quantum yields ranging from 32 to 61 %. The presence of co-ligands in the complexes significantly increases the photophysical parameters, particularly in the solid state. The energy transfer rates and back energy transfer rates of the complexes are determined. The complexes showed pure red emissions with CIE color coordinates as x = 0.66 and y = 0.33 (612 nm), suggesting their possible use as red component in organic light emitting devices (OLEDs). In particular, complex 4 exhibits the highest efficiency and stability. As a result, this complex– as an emiiting component– was tested in an OLED with a multiple layer structure.