Synthesis and spectroscopic behavior of highly luminescent Eu3+–dibenzoylmethanate (DBM) complexes with sulfoxide ligands

Abstract In this paper the synthesis, characterization and photoluminescent behavior of the [RE(DBM) 3 L 2 ] complexes (RE = Gd and Eu) with a variety of sulfoxide ligands; L = benzyl sulfoxide (DBSO), methyl sulfoxide (DMSO), phenyl sulfoxide (DPSO) and p -tolyl sulfoxide (PTSO) have been investigated in solid state. The emission spectra of the Eu 3+ –β-diketonate complexes show characteristics narrow bands arising from the 5 D 0  →  7 F J ( J  = 0–4) transitions, which are split according to the selection rule for C n , C nv or C s site symmetries. The experimental Judd–Ofelt intensity parameters ( Ω 2 and Ω 4 ), radiative ( A rad ) and non-radiative ( A nrad ) decay rates, and R 02 for the europium complexes have been determined and compared. The highest value of Ω 2 (61.9 × 10 −20  cm 2 ) was obtained to the complex with PTSO ligand, indicating that Eu 3+ ion is in the highly polarizable chemical environment. The higher values of the experimental quantum yield ( q ) and emission quantum efficiency of the emitter 5 D 0 level ( η ) for the Eu-complexes with DMSO, DBSO and PTSO sulfoxides suggest that these complexes are promising Light Conversion Molecular Devices (LCMDs). The lower value of quantum yield ( q  = 1%), for the hydrated complex [Eu(DBM) 3 (H 2 O)], indicates that the luminescence quenching occurs via multiphonon relaxation by coupling with the OH-oscillators from water molecule coordinated to rare earth ion. The pure red emission of the Eu-complexes has been confirmed by ( x , y ) color coordinates.