Synthesis, characterization, spectroscopic study and thermal analysis of rare-earth picrate complexes with l-arginine

Abstract

Rare-earth picrate complexes with l-arginine were synthesized and characterized. Analysis of carbon, hydrogen, nitrogen and thermal analysis data suggest a general formula Ln(pic)3·2l-Arg·2H2O (Ln=La–Lu, Y, pic=picrate, l-Arg=arginine). IR spectra indicate the presence of water molecules and suggest that l-arginine is coordinated to the central ion through the nitrogen of the amine group. Bands due to picrate ions also indicate that at least in part they are coordinated as bidentate through the phenoxo group and one oxygen of an ortho-nitro group. X-ray diffraction powder pattern results indicate that these complexes are very similar in structure. The parameters obtained from the absorption spectrum of the solid Nd compound indicated that the metal–ligand bonds present weak covalent character. The emission spectra of the Eu compound indicate the existence of different europium coordinaton environments. Thermal analyses results indicated that all the compounds present a similar behavior.