Spectroscopic study of RE complexes with aliphatic dicarboxylate ligands

Abstract

The metal carboxylate complexes possess a great variety of applications such as porosity, gas storage, catalyses, medical and optical markers. This work reports the synthesis and systematic spectroscopic study of a class of compounds with general formula [RE2(L)3·x(H2O)]y(H2O), where RE = Eu3+, Gd3+, Tb3+, “x” values varying from 2 to 6, “y” values varying from 0 to 4 and L is an aliphatic dicarboxylate containing from 2 up to 12 C atoms. The complexes [RE2(L)3·x(H2O)]y(H2O) were synthetized based on literature [1] with yield values around 90% by coprecipitation method. The complexes were characterized via elemental analysis (CHN), thermal analysis (TG), X-ray diffraction (XRD) infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The CHN, FTIR and TG indicate that the complexes are hydrated. The FTIR spectra indicate that the ligand-metal bonds are via chelate-bridging. The XRD patterns indicate high crystallinity and the systems are isomorphic to the same ligand. The emission spectra, represented by the azelate complexes of Eu3+ and Tb3+, present a highly intense red and green-color emission under UV excitation (254 nm), respectively to the Eu3+ and Tb3+ ions. Moreover, characteristic narrow emission bands arising from the 5D0→7FJ (J = 0-4) transitions of Eu3+, 5D4→7FJ (J = 6-0) transitions of Tb3+. The splitting of emission bands of Eu3+ complexes suggests high crystallinity and low symmetry around the metal ion, supporting the XRD data