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 C2v 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.