Correlation between structural data and spectroscopic studies of a new β-diketonate complex with trivalent europium and gadolinium

Abstract

This paper reports the study of structural and luminescence parameters of a seven-coordination compound containing β-diketone butyl methoxy-dibenzoyl-methane (bmdm) and triphenylphosphine oxide (tppo), both acting as antennae. The complex was obtained by substitution of water molecules in the [RE(bmdm)₃(H₂O)₂] precursor, where RE = Eu³⁺ or Gd³⁺. The structural data determined by X-ray monocrystal diffraction reveal that the compound crystallizes in a triclinic space group P and the coordination polyhedron is near a capped trigonal prism, with a symmetry site near a C_2v point group. The ground state geometry was determined using Sparkle/AM1 implemented in mopac2009 software, and compared with that obtained by monocrystal. The triplet (T) and singlet (S) levels were determined using INDO/S-CIS implemented in the Zindo software, the results obtained are very close to the experimental measurements. The intensity parameters Ω₂ and Ω₄ were calculated from emission spectrum. The high value of the Ω₂ parameter (37.2 × 10⁻²⁰ cm²) shows a highly polarizable environment around the europium ion and a high degree of covalence between the ligand and metal, showing that tppo molecules contribute to an increase in the covalence between the metal and ligand. The transfer rates show a predominance in the transfer process when compared with back transfer ones, with the main channel of transfer processes: T → ⁵D₁ and T → ⁵D₀.