Synthesis, characterization and thermal behavior of some addition compounds between rare earth picrates (pic) and 2,2′-dithiobis(pyridine-N-oxide)

Rare earth picrates addition compounds with 2,2′-dithiobis(pyridine-N-oxide) (dithio) were synthesized and characterized. CHN analysis suggest a general formula Ln(pic)3·1.5dithio·4H2O (Ln = La, Nd, Eu, Dy, Ho). IR spectra indicate: (a) the presence of water molecules; (b) the presence of picrate in bidentade form; and (c) a bond of dithio to the RE through NO groups. Parameters, calculated from Nd absorption spectra at room temperature are in agreement with a small covalent character of the Ln:L interaction. Thermogravimetric data under N2 and air atmospheres, show that: (a) the water molecules loss is the first decomposition step (up to 453 K); (b) the residue, at ca. 1173 K, is essentially Ln2O3.