Near infrared spectroscopic properties of new beta-diketonates lanthanide complexes with different phosphine oxide ligands

Abstract

The present work reports the synthesis, characterization and luminescent properties of the Ln3+--diketonate complexes, Ln(-dik)2(NO3)L2, Ln()3L2 and Ln(DBM)3L, where Ln3+ = Pr3+, Nd3+, Sm3+, Er3+ and Yb3+, -dik = thenoyltrifluoroacetone (TTA) and dibenzoylmethane (DBM), L = triphenylphosphine oxide (TPPO), tributylphosphine oxide (TBPO), and trioctylphosphine oxide (TOPO). The complexes were characterized by complexometric titration with EDTA, CHN elemental analysis, IR spectroscopy (FT-IR) and thermogravimetric analysis (TGA) [1]. Single-crystal X-ray diffraction analyses reveal that Ln(DBM)2(NO3)(TOPO)2 complexes crystallize in the monoclinic space group P21/c with parameters cell: a=36.727 Å; b=13.752 Å; c=15.836 Å; =90°; =93.09° e 90°. Photoluminescent properties in the near infrared (NIR) region were investigated from excitation and emission spectra. Excitation spectra are characterized by the presence of large bands associated with transitions centered on organic ligands, indicating that these ligands act as good sensitizers for Ln3+ ions that exhibit luminescence in the NIR region. The emission spectra in the NIR region of the bis- and tris-diketonate complexes of Pr3+, Nd3+, Sm3+, Er3+ and Yb3+ ions present the set of intraconfiguration transitions, characteristic of each metal center (Figure 1) [2]. Furthermore, it was observed that changes in the nature and number of ligands coordinated to the Ln3+ ion slightly influence the spectral profiles. The results obtained from the studied systems suggest that these are potential candidates to act as Molecular Light Converting Devices.